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A study of certain physiological phases of drought resistance

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A STUDY OF CERTAIN PHYSIOLOGICAL PHASES
OF DROUGHT RESISTANCE
A Thesis
Presented to
the Department of Botany
The University of Southern California
In Partial Fulfillment
of the Requirements for the Degree
Master of Science in Botany
by
C.W. McLellan
August 1940
UMI Number: EP41412
All rights reserved
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a note will indicate fhe deletion.
UMI EP41412
Published by ProQuest LLC (2014). Copyright in the Dissertation held by the Author.
Microform Edition © ProQuest LLC.
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o'
11
T h i s t hesis, w r i t t e n b y
CIU^ES„WILF^
......
u n d e r t h e d i r e c t i o n o f h%.S . . F a c u l t y C o m m i t t e e ,
a n d a p p r o v e d b y a l l its m e m b e r s , has been
p r e s e n t e d to a n d a c c e p t e d b y t h e C o u n c i l on
G r a d u a t e S t u d y a n d Research in p a r t i a l f u l f i l l ­
m e n t o f the r e q u ir e m e n ts f o r the d egree o f
MASTER OF SCIENCE
Dean
Secretary
D a te ... AUGUST
1-940
F aculty Com m ittee
Chairm an
i( 0
c
ACKNOWLEDGMENTS
Appreciation is expressed by the writer to Dr. G.R.
Johnstone for his supervision and many helpful suggestions
in carrying out the experiments, and in organizing and
writing this paper.
Appreciation is also expressed to:
C.J. King, Director of the United States Field
Station at Sacaton, Arizona, for the loan of the equipment
used by J.A. Harris in finding osmotic pressures, and for
extending the use of their laboratory to me,
R.H. Peebles, Associate Agronomist of the United
States Field Station at Sacaton, Arizona, for his verifi­
cation of my plant identifications,
Dr. G.M. Bateman, of the Arizona State Teachers
College at Tempe, for the loan of a Beckman thermometer,
and to Dr. I.B. Judd, of the Arizona State Teachers
College at Tempe, for the use of an electric oven.
TABLE OF CONTENTS
INTRODUCTION ...............................
1
REVIEW OF LITERATURE
..........
4
........................
4
Osmotic Pressure
Bound and Free Water
....................
7
. ....................
10
MATERIALS AND M E T H O D S ......................
12
Rate of Water Loss
Collecting of Samples ............ .
12
Determination of Osmotic Pressure • • • • •
12
Determination of Bound and Free Water . . .
15
Moisture Percentage • • • • •
............
17
Determination of Water Loss
.......... .
17
DATA AND RESULTS ...........................
18
Introduction to Data on Osmotic Pressure
Introduction to Data on Rate of Drying
18
, .
32
INTERPRETATION OF DATA ......................
49
Incipient Transpiration and Rate of Drying.
49
DISCUSSION .................................
The Significance of Osmotic Pressure
. . .
56
56
The Role of Bound Water in Living
............... • • • •
58
S U M M A R Y ...................................
62
Organisms
Diversities in Placement of Plants
• • • •
62
CONCLUSION......................... .. . . .
66
LITERATURE CITED ............................
69
LIST OF TABLES
TABLE
I.
PAGE
LIST OF SPECIES INVESTIGATED AT TEMPE, ARIZONA .
13
DATA ON OSMOTIC PRESSURE......................
21
III.
DATA
. '...................
26
IV.
DATA
D R Y I N G .................
33
II.
ON
ON
BOUND WATER
RATE OF
V. PLANTS ARRANGED ACCORDING TO OSMOTIC PRESSURE
.
51
VI. PLANTS ARRANGED ACCORDING TO PER CENT OF
BOUND WATER . . . . . .
.....................
52
VII. PLANTS ARRANGED ACCORDING TO MOISTURE
PERCENTAGE BASED ON DRY LEAF WEIGHT . . . . .
53
VIII. RELATIVE POSITION OF EACH SPECIES DETERMINED
BY ITS INCIPIENT TRANSPIRATION, (COLUMN l)
AND SUBSEQUENT POSITIONS (COLUMNS 2,3,4,5)
AS DESICCATION CONTINUED
.................
IX. TOTAL PER CENT OF WATER LOST AFTER EACH
WEIGHING
54
,
. . . . . .
55
X. PLANTS ARRANGED TO SHOW THEIR RELATIVE
POSITIONS AS DETERMINED BY THE OSMOTIC
PRESSURE, PER-CENT OF BOUND WATER, PER CENT
OF FREE WATER AND INCIPIENT TRANSPIRATION . .
XI.
64
SPECIES ARRANGEMENT ACCORDING TO THE OSMOTIC
PRESSURE FOLLOWED BY THE PER CENT OF BOUND
WATER AND PER CENT OF FREEW A T E R ............
XII.
65
PLANTS ARRANGED TO SHOW RELATIVE DEGREE OF
DROUGHT RESISTANCE OF EACH SPECIES AS SHOWN
BY AVERAGE OF ALL FACTORS ASGIVEN IN TABLE X
68
A STUDY OF CERTAIN PHYSIOLOGICAL PHASES
OF DROUGHT RESISTANCE
CHAPTER I
INTRODUCTION
The migration of land plants from the aquatic to the
terrestrial habitat (Bower 1908) required many important
morphological and physiological changes in the evolution of
the plant kingdom.
The further migration of plants into
the driest regions of the world has been possible through
extended modifications of structure and behavior of plants.
In the deserts of the world plants display the highest ex­
pression of such modifications.
Extensive and intensive investigations (Maximov
1935) have been made in attempts to explain the peculiar
survival value of the morpho-physiological mechanisms which
have made possible the invasion of the desert by the plant
kingdom.
The value of this previous work, while it has
not given a complete explanation of drought resistance, has
been to show that the full explanation does not lie in
these certain fields, and therefore it has given new
direction to later work.
The impetus back of much of the earlier work was to
find the structures that drought resistant plants possess
and to examine the cultivated plants for such structures
in search for varieties suited for growth under arid condi­
tions .
Another avenue of investigation dealing with inter­
nal factors, such as the plant sap (Harris 1914-25) is now
gaining prominence as a more important factor in drought re­
sistance*
Maximov (1955) states that the center of interest
of the problem of drought resistance is, in. fact, tending to
be transferred to the specific properties of the protoplasm
of different plants*
An analogy has been drawn between winter hardiness
and drought resistance of plants*
Martin (1931) believes
that winter hardy varieties of a plant tend to have a lower
moisture content, higher concentration of solids and bound
water in the cell sap, and a greater ability to elaborate
hydrophilic colloids than do non-hardy varieties.
Drought
resistant plants may have a higher osmotic cell-sap concen­
tration or a higher imbibition pressure and a high content
of bound water, due to abundant colloidal material in the
protoplasm*
The work of other investigators (Boswell 1923) indi­
cates that hardy plants lose water less rapidly than do
plants of more tender tissue.
It is to be supposed that
drought resistant plants must necessarily carry a low content
of moisture in the leaves*
The above statements have been concluded from experi­
ments carried on at different times on many different plants*
No literature deals with data on simultaneous measurements of
all the factors, namely, water content of the leaves, rate of
loss of water, amount of bound and free water, and the osmotic
pressure measured from each plant at the same time*
This paper will deal with these four factors measured
from each plant at the same time*
An attempt will be made
to establish the degree of relationship existing between the
four factors*
Knowing the relationship and one of the fac­
tors it should be possible to predict the approximate value
of the others*
CHAPTER II
REVIEW OF LITERATURE
Osmotic Pressure. - The study of osmotic pressure,
by determining the lowering of the freezing point, and its
importance to plant life has been of continued interest to
botanists since 1886*
At this date MtLller-Thurgau deter­
mined the freezing point lowering of ground plant parts.
Maguenne, in 1896, obtained cryoscopic measurements of ex­
pressed juices of sunflower and pea seedlings.
This type
of work was followed in 1901 by Sutherst, who determined
the freezing points of turnip, celery, carrots, cabbage,
apple and peas.
Livingston (1906) used the freezing point
and boiling point methods and found that cacti have no high­
er osmotic pressure than plants of the humid regions.
E. and Hilda Drabble (1907), using the plasmolytic
method while working on the relation between the osmotic
strength of cell sap in plants and their physical environ­
ment, drew conclusions which have been verified by other in­
vestigators and are now stated under the general laws
In
plants of the same species growing under the same conditions
of water supply, the osmotic strength of the cell sap is
generally the same, and that in any area the osmotic strength
of the cell sap varies indirectly with the physiological
scarcity of water.
Hans Fitting (1911) also using the plasmolyt&c method,
worked in the Sahara desert and examined forty-six species
of plants growing in oases, saline soils, rocky wastes and
sand dunes.
He found the highest pressures in the plants
growing in dry soil and no extremely high pressures in
moist soils.
The most extensive investigations in osmotic pres­
sure as determined by the depression of the freezing point
have been carried out by Harris and his co-workers.
In
1914 H,A, Gortner and J,A, Harris published their technique
for the determination of the depression of the freezing
point of vegetable saps.
During the same year Harris and
Gortner developed a table from which the osmotic pressures
could be directly read for the depression of the freezing
points from 0,001° C,, to 2,999° C,
This table was extend­
ed by Harris in 1915 to include the degrees up to 5.999° C.
In 1925 he published a table to facilitate the correction
for undercooling In cryoscopic work.
The osmotic pressures of the juices of desert plants
were extensively determined in 1915 by Harris, Lawrence and
Gortner.
During this time many plants of the southwest
desert regions of the United States were measured.
The re­
sults showed that in the deseapt series fifty per cent of the
pressures were 15.7 atmospheres or higher, while in the
vicinity of Tucson, Arizona, about thirty per cent of the
concentrations were over 20 atmospheres.
In 1916 Harris
and Lawrence determined the cryoscopic constants of the ex­
pressed vegetable saps, as related to the local environment­
al conditions in the Arizona deserts.
Plants growing in
the drier places, such as the rocky hillsides, gave higher
pressures than did those growing in places containing more
moisture.
Harris, in 1918, worked on the tissue fluids of
the desert Loranth&ceae and found that the osmotic pressure
e o
s
of th^s parasiteA was 28.65 atmospheres as compared to 24.50
atmospheres for its host.
The osmotic concentration of the
Arizona Loranthaceae was twice as great as that of the tis­
sue fluids of the species in the montane r&in-forests of the
Jamaican Blue Mountains.
Lawrence A. Stoddart (1935) investigated the osmotic
pressures and water content of prairie plants.
He reasoned
that since the osmotic pressure of a solution is dependent
upon the proportion of water and osmotically active substances,
it may be concluded that either a decrease in the water con­
tent or an increase in osmotically active substances will have
an identical effect, namely, an increase in the osmotic pres­
sure.
He found that osmotic pressure and water content of
tissues closely parallel each other, and are highly indicative
of the availability of water.
During the progress of the
season and as the soil dried, the osmotic pressure of all
prairie plants studied increased.
Due to the soil drying,
the water content of the tissue regularly decreased.
The
water content of plant tissue was found to be a rather exact
indicator of osmotic pressure, plants with high pressures
usually having low water content and plants with low pres­
sures usually having high water content.
New growth of
plant tissue had a higher water content and a lower osmotic
pressure than old tissue.
Artificial watering in late slim­
mer lowered osmotic pressures and increased the water con­
tent of the plant tissues.
Bound and Free Water. - J.D. Sayre (1932) defines
bound water as
All water that does not show some of the common
properties of liquid water may be considered as
bound water.
He gives the three methods of finding bound water
as the cryoscopic, the calorimetric and the dilatometric
methods.
The cryoscopic method is based on the principle that
bound water is not free to dissolve sucrose.
A determina­
tion of the increased depression of the freezing point of
the material after sucrose is dissolved in it will indicate
whether or not all the wqter present is free for the solution
of sucrose.
liquid state.
This method can be used only on material in the
The addition of sucrose may cause a change in
the bound and free water equilibrium.
The calorimetric method makes use of the fact that
bound water does not freeze.
In this method the material is
frozen and water that changes to ice is determined by measur­
ing the heat necessary to thaw the frozen material.
This
method can be used on any kind of material.
The dilatometric method assumes that bound water does
not freeze and by measuring the expansion of the material dur­
ing freezing determines how much water changes to ice, the
drawbacks being that all air must be removed and that the
8
bound and free water equilibrium may be changed by freezing*
D*R. Briggs (1932) writing on the bound water in col­
loids states
All methods of finding bound water are consistent
in that they subject the total water in the system
to a set of conditions which remove or change the
state of a fraction of that water, leaving a portion
unaccounted for, this being designated as bound water*
A portion of the water in a system is associated with
the colloid phase with such strength that it is no
longer free to exhibit those properties which are
characteristic of water, i.e*, it is no longer avail­
able to act as a solvent, or it cannot be separated
from the colloid by freezing or by subjecting the sys­
tem to pressure, as in the ultrafilter.
This water
can, however, be removed by ordinary drying at 100©
C., or under a vacuum at ordinary temperatures.
Briggs defines bound water as
... that portion of the water in a system containing
colloid and crystalloid which is associated with the
colloid together with those ions which form a part
of the colloid complex.
Bound water is not a fixed
quantity of water associated with the colloid but
will vary with the activity of the water in the sys­
tem in a manner consistent with the vapor pressure
isotherm of the colloid.
E.V. Lebedentseva, working in Russia in 1930 on the
question of water-retaining capacity of drought and cold re­
sistant plants by means of the dilatometer, found that the
xerophytes of the semi-desert zone of Azerbeidschan are dis­
tinguished by a higher water retaining capacity than mesophytes grown in the same conditions.
If he increased the
drought resistance of plants by cultivating them at a low
soil moisture or subjecting them to repeated wilting, the
plants thus hardened increased their water-retaining capa­
city.
This increased capacity of retaining water is main­
tained by plants after their recovery from wilting.
The
9
amount of bound water in cold resistant plants was higher
than in the non-resistant ones.
G.A. Greathouse (1957) obtained direct correlation
between bound water and hardiness.
An analysis of his re­
sults led to the conclusion that bound water and osmotic
pressure are not closely correlated.
Hardiness was found
to be more closely correlated with bound water.
He stated
It is probable that the increase in bound water
is at least partly due to that bound by sugars,
which may be present in larger quantities even in
plants with a lower osmotic pressure.
The results of J. Levitt (1939) showed cabbage tissue
has about twice as much ice per gram of dry matter in the
unhardened as in the hardened plants.
The plants when
hardened retain a slightly larger quantity of unfrozen water
per gram of dry matter than did the unhardened.
The Outlines of Biochemistry, by Gortner, give the
results of the unpublished work of Harris (1922) using cer­
eals which were growing under dry-land farming conditions
and under irrigation in Utah.
It was found in general that
when cereals have an abundant supply of moisture, there is
relatively little tendency for the development of hydro­
philic colloids and the elaboration of bound water;
whereas,
when they are growing in conditions of stress, the onset of
drought causes a greater proportion of the water in the tis­
sues to be transformed from a free to a bound condition.
Newton (1922) in Alberta, has continued the studies of
bound and free water as related to drought resistance and has
demonstrated quantitatively that drought resistance of agri-
cultural crops and of native grasses is related to, or at
least that drought resistant varieties can be differentiat­
ed by bound water content.
J.H. Martin (1931) summarized the work on winter
hardiness and drought resistance as follows
Winter hardy varieties of plants tend to have a
lower moisture content, higher concentrations of
solids and bound water in the cell sap, a lower rate
of respiration at low temperatures, and a greater
ability to elaborate hydrophylic colloids than do
non-hardy varieties.
Drought resistant plants may
have a high osmotic cell sap concentration, or a high
imbibition pressure and a high content of bound water,
due to abitfidant colloidal material in the protoplasm.
Rate of Water Loss. - V.R. Boswell in 1923, made in­
vestigations to determine (l) J&ie relative water retaining
capacity of the tissues of plants subjected to different
treatments and of known degrees of hardiness, and (2) ^wiiether there is a close correlation between the relative amounts
of free and unfree water in such tissues and their rates of
drying.
Cabbage and tomato leaves were used throughout the
experiment.
The results show that hardy tissue lost water
less rapidly than tender tissue.
The hardening treatment
had not resulted in the development of any considerable water
retaining power in the tomato leaves, but cabbage did show a
difference.
The figures show a close correlation between the de­
gree of hardiness and rate of water loss.
Hardy tissue lost
its water slowly in the early periods of drying and had more
to lose in the later periods.
The curve in very hardy tis­
11
sue is almost a horizontal line, indicating that its water is
held more tenaciously than in the tender tissue.
The water
that is held so firmly is presumably in colloidal combina­
tion, while that which passes off early is probably free
water.
In the cabbage, thirty to forty minutes drying at
60° C., removed practically all the free water, as determined
by dilatometer experiments, and the differences in the heights
of the curves at that point indicate approximately the rela­
tive amounts of colloidal water.
Boswell states
The results suggest that the method of drying des­
cribed in this paper may be used to estimate the rela­
tive amounts of free and unfree water in plant tissue,
and comparative rates of water loss are a measure of
the relative hardiness of certain kinds of plant tis­
sues .
CHAPTER III
MATERIALS AND METHODS
Collecting of Samples. - The material used in this
investigation consisted so far as possible of the leaf blade
and petiole.
Collections for the determination of osmotic
pressure, bound water and rate of drying were made in dupli­
cate from the same plant or plants at the same time and were
deposited in three separate types of containers.
An effort
was made to have each sample consist of an equal distribution
of leaves of the same age or stage of development.
Each
collection was made during the same time of the day, that is,
during the hours from eleven o ’clock A.M., to two o ’clock
P.M., since investigations (Livingston and Brown, 1912, Maxi­
mov and Krasnoselsky-Maximov, 1924, Kusmin, 1930) have
shown that during this time of the day the water deficit in
plants is at its maximum.
It was thought that at this time
the difference for each plant would be more pronounced and
thus small differences would be less likely to be overlooked.
Table I contains a complete list of the plants inves­
tigated.
The scientific names are given according to Munz
(1939), A Manual of Southern California Botany}with the ex­
ception of Eucalyptus globulus Labil.. and Ligustrum japonicum Thuub., from Bailey’s (1925) Manual of Cultivated Plants.
Determination of Osmotic Pressure. - The leaves, as
rapidly as collected, were placed in ln x 8n test tubes,
which were tightly stoppered as soon as they were filled.
13
TABLE I
LIST OF SPECIES INVESTIGATED AT TEMPE, ARIZONA
Plants Arranged Chronologically by Dates of Collection*
Species
Date
Water Relations
Medicago sativa L.
July 7, 1939
Prosopis chilensis
(Molina) Stuntz
Atriplex elegans
(Moq) Dietr,
Salsola kali L,
Olneya tesota Gray
July 7, 1939
Larrea divaricata
Cav.
S&lix gooddingii
Ball
Populus fremontii
Wats •
Brusera microphylla
Gray (New leaves)
Amaranthus palmeri L,
July IS
July 12
July 15
July 15
July 17
July 17
July 19
July 19
Irrigated ten days
previous
Occasionally wet
1939 Growing along a dry
roadside
1939 Dry fence row
1939 Growing in a dry sandy
wash
1939 Growing in a dry sandy
wash
1939 Growing on bank of
stream
1939 Growing on bank of
stream
1939 Dry rocky hillside
July 25
1939 Fence row of citrus
grove
1939 Irrigated ten days
previous
1939 Foot of Tempe Butte*
Dry rocky hill
1939 Growing in river
July 25
1939 Hedge\ moist soil
Ricinus communis L,
July 19
Atriplex polycarpa
(Torr,) Wats,
Rorippa nasturtiumaquaticum L.
Schinz and The11,
Ligustrum japonicum
Thunb,
Eucalyptus globulus
Labil, (Adult
leaves)
Eucalyptus globulus
Labil.(Juvenile
leaves)
July 25
Aug. 3, 1939
Aug. 3, 1939
Parking lot back of
Science Building,
U.S.C. Campus, L.A.
Parking lot back of
Science Building,
U.S.C. Campus, L.A.
*The habitat or habitat characteristics are given in the
last column.
Since the lapse of time before being placed in the freezing
chambers of an electric
ice box was short itwas not necessary
to place them in an ice
bath in the field.
left the remaining part
of the day and overnight at a temper­
ature of a minus 5 to 9
degreesCentigrade.
The tubes were
When the leaves
were removed from the tube they were wrapped in a heavy
square of muslin and pressed in a completely tinned, steel
cylinder.
The plant sap was poured into a glass tube and
centrifuged at a high speed.
Before determining the freez­
ing point the sap was cooled in an ice and water mixture.
The tube containing the sap was then placed in the freezing
jacket which was surrounded by a salt and ice mixture of a
minus 12 to 15 degrees Centigrade.
The depression of the
freezing point was recorded with a Beckman thermometer.
This
reading was repeated twice and if a variation of over 0.01 of
a degree was found, several readings were made and an average
of the readings was taken as the final result.
The zero
reading of the thermometer was determined before using each
day.
For the correction of the depression of the freezing
point the formula, (Gortner and Harris, 1914)A = (l - 0.0125 u)
A*, was used.
Where
A = the true depression of the freezing
point, A* = the observed depression, and u=degrees undercool­
ing.
To speed up the calculations the table of Harris (1925)
for the value of 1 - 0.0125 u was used.
From the depression
of the freezing point the osmotic pressure was calculated by
use of the formula (Gortner and Harris, 1914)
P = 12.06 - 0.021 A 8
15
The results were later checked by the tables of Harris
and Gortner (1914) and Harris (1915) .
For each unit in the
third decimal place 0.012 of an atmosphere was allowed.
Determination of Bound and Free Water. - Heavy walled
glass tubes
x 9tt which were open at both ends, were filled
with leaves and stoppered.
The tubes, upon returning from
the fields, were immediately weighed to the nearest tenth of
a gram and placed in the freezing chambers of the electric
refrigerator.
The temperature of the freezing chamber was
recorded with a double scaled thermometer graduated from minus
0.0 degrees Fahrenheit to 110 degrees Centigrade.
The
temperature of the plant tissue at equilibrium was found to
be minus 5 degrees Centigrade.
Due to the routine of the
work, the tubes were allowed to remain in the freezing cham­
bers for about 20 hours.
The leaves were then transferred to
the calorimeter and their heat capacity determined by the
change in the temperature of the water.
A wide-mouthed pint
thermos bottle fitted with a cork stopper through which a 0.1
degree Centigrade thermometer was inserted served as a calori­
meter.
For each determination it was emptied, dried and re­
filled with 200 grams of water.
By means of a lens the read­
ings were taken to the closest 0.010 C. when at equilibrium.
The thawed leaves were taken from the calorimeter, dried at
105° C., weighed, placed in the freezing chambers, allowed to
/
establish an equilibrium and the heat capacity of the dry mat­
erial was determined in the same manner as for the green mat­
erial.
The specific heat of the dry material was calculated
by the formula (Loomis and Shull, 1937)
d
~
where the symbols have the same meaning as in the following
equation (Loomis and Shull, 1937), which was used to find
the weight of free water in the leaf tissue
W =
FgSw (tc -•*«> - fasd<*e - V +
h - (sw - Sl)
WSw(*e ~
(tm - tf)
Where w is the free or frozen water,
F is the calorimeter factor
g is the weight of water in calorimeter
d is the weight of dry sample
Sw is the average specific heat of water
S3 is the specific heat of ice
S3 is the specific heat of dry material
W is the total water in leaves
t„ is the original temperature of calorimeter
V
te is the equilibrium temperature of calorimeter
is the freezing temperature used
tm is the melting point of expressed sap
h is the heat of fusion of ice (80)
This equation has as its basis the fact that one small
calorie of heat will warm a gram of water from 0 to 1° C.,
but 81 calories are required to warm a gram of ice through
the same range, 80 calories to melt the ice and one calorie
to warm the water formed.
This energy difference is used to
17
distinguish between frozen and unfrozen water in a tissue
of known total-water content*
Subtracting the free water
from the total water in the leaf gives the total bound
water.
The total water is the difference between the weight
of the green leaves and their weight when dry.
The final re
suits are reported in percentage using the dry leaf weight as
a basis.
Moisture Percentage, - Two checks on the moisture per­
centage were possible.
One was taken from the water content
found in the determination of bound water.
The second
moisture percentage was the difference between the green and
dry leaf weight found in the rate of drying of hardy and non­
hardy tissue.
Determination of Water Loss. - The leaves were select­
ed so as to represent an average of all leaves on the plant.
Duplicate samples were taken for each determination.
dishes
Petri
inches in diameter by f inch in depth were used as
containers.
Due to the ease and rapidity with which this
type of container could be opened and closed it was found to
be best suited to this type of work.
As soon as the dishes
were filled they were closed, taken to the laboratory, the
covers removed and the dishes placed in an electric oven at
60° C.
At the end of a fifteen minute period the dishes
were taken from the oven, immediately closed, weighed, the
lids again removed and the dishes replaced in the oven.
This routine was kept up at the rate of three weighings per
hour for at least three hours.
CHAPTER IV
DATA AND RESULTS
Introduction to Data on Osmotic Pressure. - Readings
were taken for the following factors of the formula
A
equals (l - 0.0125 u ) A »
where the symbols stand for
A
equals true depression
A 1 equals observed depression
u
equals degrees undercooling
The thermometer used was graduated for boiling point
determinations, which read from zero up to five, rather than
from zero down to five;
hence the readings for the freezing
points are in the reverse order.
The first figures in the following data represent the
point on the thermometer at which the sap was found to freeze.
This point has been designated as H^O - A f, since mathemati­
cally it is the difference between the freezing point of pure
water and the observed depression of the freezing point of
the plant sap.
The freezing point of pure water is taken as
the zero point of the thermometer.
The lowest point to which
the thermometer drops is recorded as u f.
The degrees under­
cooling is the difference between the point on the thermo­
meter at which the sap freezes and the lowest point to which
the mercury drops before freezing starts.
Subtracting the
thermometer reading at which the sap froze from the point at
which the pure water froze gives the observed depression of
19
the freezing point of the plant sap, which is called A T.
Water will give a constant temperature reading during
freezing, hut the readings for solutions tend to drop contin­
uously as water is crystallized out, leaving a more concen­
trated solution (Loomis and Shull, 1937).
Because the un­
dercooled solution is warmed by ice formation, even the high­
est reading is below the true freezing point of the solu­
tion when undercooling occurs.
The formula as stated is
used to correct for this low freezing point and large freez­
ing point depression.
If 80 ml, of a solution is undercooled 1° C. before
ice formations starts, the freezing of 1 ml, of the water in
solution will be required to furnish heat to warm the system
up to the freezing point.
The removal of 1 ml, water will,
however, concentrate the solution one-eightieth and thus give
too low a freezing point reading, or too much freezing point
depression.
In general, the apparent lowering of the freez­
ing point is too large by one-eightieth for each degree of
undercooling.
If v equals the volume of the solvent and u
equals the degrees of undercooling of the solution, then
uv/80 represents the volume of the solvent removed, and
v - uv/80 represents the volume of the solvent remaining in
the solution after the formation of ice due to undercooling.
The latter formula simplified becomes
v - 0,0125uv
or
v(l-0,0125u)
Since the observed depression is too large in propor­
tion to the volume of the solvent removed, the formula for
correction can be stated as
A equals A 1 - 0.0125u A *, or A equals A 1 (l - 0.0125u)
21
TABLE II
DATA ON OSMOTIC PRESSURE
jStsO
Rorippa na stur tlum-aoua ti cum
Ho0 4.730
% 0 - At 3.915
u 1 0 f),7P..%0 - A 1 & J 00 A equals 0.777
A* .815
u 3.745
P equals 9*358
3.905
JsxJLQjQL ..
2.805
4.730
3.,AQ5 Aequals 0.796
.825
P equals 9.586
3.934
X mSDSL
2.734
4.730
&J3S& A equals 0.7706
.798
P equals 9.286
3.934
4.730
5*213- A equals 0.7787
.819
0.000
3.934
P equals 9.382
4)37.612
9.403
Bursera mlcrophvlla
3.719
0.830
2.989
4.730
P * Z M A equals 0.973
3.735
1.730
4.730
3.735 A equals 0.970
P equals 11.716
1.011
-
P equals 11.680
8)28.596
11.698
Salix goodinsii
3.528
0.650
2.878
4.730
2«S80 A equals 1.159
P equals 13.949
3.498
=•800.
3.798
4.730
3.498 A equals 1.173
1.232
P equals 14.117
3.495
4.730
3.495 A equals 1.176
1.235
=•2201
3.795
1.202
P equals 14.153
5)48.219
14.073
22
TABLE IX (Cont'd)
DATA ON OSMOTIC PRESSURE
Medicaeo sativa
Original data not available
equals 1.22
P equals 14.68
Amaranthus iwlmer-1
* 3.185
H2O 4.730
' -.040 H 0 -A» 3.185
. 3.225
A' 1.545
3.200
-.050
3.250
4.730
3.200
1.530
A equals 1.477
P equals 17.764
A equals 1.470
P equals 17.68
2)35.444
17.722
Ricinus nnmiminl a
3.113
0.740
2.373
4.730
3.113
1.617
A equals 1,569
P equals 18.868
3.145
A equals 1.542
P equals 18.544
2.145
4.730
3.145
.1.585
3.120
0.050
3.170
4.730
3.120
1.610
A equals 1.546
-
P equals 18.592
3)56.004
18.668
1.000
Pnmibia fremontil
3.017
-.500
3.517
4.730
3.017
1.713
A equals 1.638
P equals 19.698
3.060
0.250
3.310
4.730
3.060
1.670
A equals 1.601
P equals 19.275
3.030
-.400
3.430
4.730
3.030
1.700
A equals 1.627
P equals 19.587
3)58.560
19.520
23
TABLE II (Cont'd)
DATA ON OSMOTIC FEESSORE
Salsola kali
* 3.030
HoO
4.728
f. 0.880 HgO - A f 5.050 A equals 1.652
2.150
A ‘ 1.698
3.000
0.600
2.400
4.728
5.028 A equals 1.649
1.700
P equals 19.84
P equals 19.83
Salsola kali f Second sample
3 005
0.150
2.855
4.728
5.005 A equals
1.723
1.66
P equals 19.96
2.995
-.500
3.295
4.728
2 7995 A equals
1.733
1.66
P equals 19.96
2 989
-.700
3.689
4.728
2.989 A equals
1.739
1.65
P equals 19.84
5)99.45
19.886
Prosopis chilensis
Original data not available.
A equals 1.625
P equals 20.48
Ligustrum .lanonicum
2.828
-.400
3.228
4.730
2.828 A equals 1.835
1.902
P equals 22.06
2.828
-.400
3.228
4.730
2.828 Aequals 1.835
1.902
P equals 22.06
24
TABLE II (Cont'd)
DATA ON OSMOTIC PRESSURE
tesota
-
HpO 4.735
« 0.780 HpO - A t 2.860 A equals 1.826
8*080
A 1 1.875
P equals 21.95
8*678
-.800
3.478
4.735
£*678 A equals 1.967
2.057
P equals 23.64
8*830
-.400
3.230
4.735
2 1830 A equals 1.838
1.905
£C
HgO - A * 8*860
P eauals 22.09
3)67.68
22.56
Larrea dlvaricata
8.296
-.300
2*596
4.735
2.296 A equals 2.360
2.439
2.303
-.500
2.803
4.735
2.303 A equals 2.347
2.432
P equals 28.345
P eauals 28.19
2)56.535
28.267
Atriulex eleeans
0.593
-1.500
2.093
4.735
0.593 A eauals 4.034
4.142
P equals 48.31
0.360
-2.050
8.410
4.735
Q*36fl A equals 4.243
4.375
P equals 50.80
0.491
-1.600
2.091
4.735
Q■4,9,1 A equals 4.133
4.244
P eauals 49.49
3)148.600
49.53
25
TABLE II (Cant'd)
DATA ON OSMOTIC PRESSURE
Atriplex polvcarpa
(Juice diluted, 1 cc, sap to 3 cc. water)
1 3.392
HpO 4.730
T —-400 H 0 - A 1 3>292 Aequals 1.3716
3.696
A* 1.438
3.275
0.800
2.475
P equals 16.504
4.730
A equals 1.409
1.455
P equals 16.960
2)33.464
16.732
Eucalyptus globulus. Juvenile leaves
4.038
0^330
3.708
5.012
4.038 A equals 0.929
0.974
P equals 11.188
4.041
l r260
2.981
5.012
4.041 A equals 0 •935
0.971
P equals 11.260
4.017
0 .200.
3.817
5.012
4.0A2 A equals 0.9475
0.995
P eauals 11.410
3)33.858
11.286
Eucalyptus globulusf Adult leaves
3.650
-1.300
4.950
5.012
3.650 A equals 1.288
1.362
P equals 15.496
3.675
QJZQ
3.505
5.012
3.675 A equals 1.278
1.337
P equals 15.376
3.662
-.300
3.962
5.012 A equals 1.283
3.662
1.350
P equals 15.436
3)46.308
15.436
26
TABLE III
DATA ON BOUND WATER
S. M i l
Sample Sample
one
two
Wt. tube & leaves
Wt. tube
Wt. leaves
110.30 106.60
82.10 82.00
23.60 24.60
M.
gatJLVfrB.mlcrophylla
Sample Sample Sample Sample
one
two
one
two
81.50 105.00
61.20 80.80
20.30 25.20
22.00
98.30
80.80
17.50
83.10
61.10
Cal temp, at t^
Cal. temp, at te
Temp, change
31.80
22.50
9.30
31.90
23.10
8.80
32.70
25.70
7.00
32.55
25.20
7.35
31.00
24.20
6.80
30.70
25.30
5.40
Cal. temp, at te
Leaf temp, at t^
Temp, change
22.50
-5.00
27.50
23.10
-5.00
28.10
25.70
-5.00
30.70
25.20
-5.00
30.20
24.20
-5.00
29.20
25.30
-5.00
28.30
Dish & dry leaves
Wt. dish
Wt. dry leaves
88.40
82.10
6.30
82.50
77.70
4.80
79.80
75.60
4.20
85.60
80.50
5.10
81.50
75.70
5.80
84.70
80.40
4.30
6.00
4.80
4.20
5.10
5.80
4.40
Cal temp, at tc
Cal. temp, at ze
Temp, change
30.70
30.45
0.25
29.90
29.70
31.80
31.70
30.58
30.48
0.20
0.10
31.60
31.45
0.15
0.10
31.07
31.00
0.07
Cal. temp, at te
Leaf temp, at t^
Temp, change
30.45
-5.00
35.45
29.70
-5.00
34.70
31.70
-5.00
36.70
31.45
-5.00
36.45
30.00
-5.00
35.00
31.00
-5.00
36.00
.25
.27
.19
.11
Wt. green leaves
Wt. dry leaves
Wt. total water
28.20
' 6.30
21.90
24.60
4.80
19.80
20.30
4.20
16.10
25.20
5.10
22.00
Wt. free water
HgO to be added
Total free water
18.23
17.50
0.10
0.00
18.33
Dry leaves in tube
Sp. ht. dry leaves
Total bound water
% bound water
Average % bound
water
.151
1101
20.10
5.80
16.20
17.50
4.30
13.20
13.51
12.94
13.14
10.49
0.10
0.20
0.10
0.20
17.00
14.61
13.14
13.24
10.69
3.57
2.80
2.49
6.96
3.06
2.71
16.30
14.14
15.46
34.62
18.88
20.53
15.22
25.04
19.70
27
TABLE III (Contfd)
DATA ON BOUND WATER
£• chilensis
Sample Sample
one
two
Wt. tube & leaves
Wt• tube
Wt. leaves
106.50 109.20
82.10 82.00
24.40 27.20
L. .iaponicum P. fremontii
Sample Sample Sample Sample
one
two
one
two
91.40 100.20
59.30 60.20
32.10 40.00
Cal. temp, at tc
Cal. temp, at te
Temp, change
32.56
26.10
6.46
32.30
26.40
5.90
30.60
Cal. temp, at te
Leaf temp, at tf
Temp, change
26.10
—5.00
31.10
26.40
-3.00
29.40
21.20
Dish & dry leaves
Wt. dish
Wt. dry leaves
92.20
82.40
9.80
107.80 110.80
82.00 82.00
25.80 28.80
30.80
19.40
11.40
30.95
23.60
7.35
30.80
22.70
-5.00
26.20
19.40
-5.00
24.40
23.60
-5.00
28.60
22.70
-5.00
27.70
89.40
77.60
01.80
95.80
86.80
9.00
81.80
72.40
9.40
90.00
82.50
7.50
86.40
77.60
8.80
9.80
11.80
8.80
9.20
7.50
8.70
Cal. temp, at tc
Cal. temp, at te
Temp. change
30.90
30.30
0.60
31.75
30.85
0.90
30.56
30.20
0.36
30.57
30.20
0.37
30.60
30.50
30.40
30.30
0.10
0.10
Cal. temp, at te
Leaf temp, at tf
Temp, change
30.70
-5.00
35.70
30.85
-5.00
35.85
29.90
-5.00
34.90
30.20
-5.00
35.20
30.50
-5.00
35.50
30.30
-5.00
35.30
Dry leaves in tube
Sp. ht. dry leaves
.383
.473
21.20
9.40
.25
.262
.087
8.10
.078
Wt. green leaves
Wt. dry leaves
Wt• total water
24.40
9.80
14.60
27.20
11.80
15.40
32.10
9.00
23.10
40.00
9.40
30.60
25.80
7.50
18.30
20.00
Wt. free water
HgO to be added
Total free water
11.07
0.50
11.57
9.97
18.22
23.46
14.05
15.616
0.10
0.20
0.10
0.20
10.07
18.42
23.56
14.25
15.716
3.03
5.33
4.68
7.04
4.05
4.284
20.75
34.60
20.26
22.67
23.13
Total bound water
% bound water
Average % bound
water
20.75 °
21.46
28.80
8.80
0.10
21.42
21.77 '
*
28
TABLE III (Cont fd)
DATA ON BOUND WATER
Wt. tube & leaves
Wt. tube
Wt. leaves
R. nasturtium
Sample Sample
one
two
0. tesota
Sample Sample
one
two
S., gooddingli
Sample Sample
one
two
115.30 106.10
82.10 82.00
33.20 24.10
90.00 107.20
61.20 80.80
28.80 26.40
90.70 115.30
61.00 80.80
29.70 34.50
31.50
23.80
9.40
8.20
30.85
23.40
7.45
30.60
23.30
7.30
30.20
21.10
20.30
-5.00
25.30
21.20
92.60
80.40
Cal. temp, at tc
Cal. temp, at tf
Temp, change
30.50
18.20
12.30
Cal. temp, at te
Leaf temp, at tf
Temp, change
18.20
-5.00
23.20
21.10
-5.00
26.10
23.30
-5.00
28.30
23.40
-5.00
28.40
Dish and dry leaves
Wt. dish
Wt. dry leaves
84.10
82.40
1.70
97.50
96.40
84.00
75.70
8.30
88.10
86.00
80.40
7.70
75.70
10.30
7.90
7.60
9.90
12.10
Dry leaves in tube
30.50
1.10
2 .80
21.20
9.00
-5.00
26.20
12.20
Cal. temp, at t
Cal. temp, at te
Temp, change
30.54
30.40
0.14
same
same
same
31.20
30.95
31.25
31.00
30.25
30.15
30.60
30.48
Cal. temp, at te
Leaf temp, at tf
Temp, change
30.40
-5.00
35.40
same
same
same
30.95
-5.00
35.95
31.00
-5.00
36.00
30.15
-5.00
35.15
30.48
-5.00
35.48
Sp. ht. dry leaves
.315
.315
34.50
23.00
29.70
10.30
19.40
22*66
1.00
16.79
. 15.08
13.75
14.35
18.27
.02
0.10
0.10
0.00
0.20
23.66
16.99
15.18
13.85
14.35
18.47
7.84
6.01
5.32
4.95
5.05
3.83
24.88
26.13
25.95
26.47
26.03
26.09
24.10
Wt. free water
% 0 to be added
Total free water
Average % bound
water
.062
26.40
7.70
18.70
33.20
1.70
31.50
% bound water
.064
28.80
8.30
20.50
Wt* green leaves
Wt. dry leaves
Wt. total water
Total bound water
.204
.196
1.10
25.50
26.21
12.20
22.30
26.06
TABLE III (Cont’d)
DATA ON BOUND WATER
A. nalmeri
Sample Sample
one
two
Wt* tube & leaves
Wt• tube
Wt. leaves
119.SO 108.10
82.10 82.00
37.10 26.10
R. communis
Sample Sample
one
two
89.10
60.00
29.10
95.80
59.30
36.50
Cal. temp, at tc
Cal. temp, at te
Temp, change
31.05
20.60
10.45
31.20
23.50
7.70
31.55
23.10
18.45
31.60
Cal. temp, at te
Leaf temp, at tf
Temp, change
20.60
-5.00
25.60
23.50
-5.00
28.50
23.10
-5.00
28.10
21.00
Dish & dry leaves
Wt. dish
Wt. dry leaves
92.60 102.80
82.50 96.50
10.10
6.30
93.10
86.80
80.70
72.50
6.20
8.20
Dry leaves in tube
10.10
6.30
6.20
8.10
Cal. temp, at tc
Cal. temp, at te
Temp, change
31.18
30.90
0.28
31.30
31.10
0.20
30.75
30.60
0.15
30.85
30.60
0.25
Cal. temp, at te
Leaf temp, at tf
Temp, change
30.90
-5.00
35.90
31.10
-5.00
36.10
30.60
-5.00
35.60
30.60
-5.00
35.60
Sp. ht. dry leaves
29.10
27.00
20.39
0.10
37.10
Wt. free water
HgO to be added
Total free water
% bound water
Average % bound
water
10.60
-5.00
26.00
.106
26.10
6.30
19.80
Wt. green leaves
Wt. dry leaves
Wt. total water
Total bound water
.196
.17
21.00
.193
36.50
6.20
8.20
22.90
28.30
14.89
15.61
20.26
0.10
0.10
0.10
20.49
14.39
15.71
20.36
7.51
5.41
7.19
7.94
27.44
27.32
31.40
28.05
10.10
27. 38
28.72
TABLE III (Cont'd)
DATA ON BOUND WATER
Wt. tube & leaves
Wt. tube
Wt. leaves
E. alabulys
Adult leaf
Sample Sample
one
two
92.50 115.00
61.00 81.80
31.50 33.20
Cal. temp, at tc
Cal. temp, at tf
Temp, change
25.70
19.70
E. globulus
Juvenile leaf
Sample Sample
one
two
117.20 99.00
82.00 59.30
35.20 40.70
6.00
25.70
19.40
6.30
25.70
17.00
8.70
25.05
15.95
9.15
Cal. temp, at te
Leaf temp, at tf
Temp, change
18.70
-4.00
23.70
19.60
—4 .00
23.60
17.00
-4.00
21.00
15.90
-4.00
19.90
Dish & dry leaves
Wt. dish
Wt. dry leaves
56.50
43.20
13.30
56.60
43.00
13.60
45.00
34.00
50.50
38.30
11.00
12.20
Dry leaves in tube
13.00
13.50
11.00
12.10
Cal. temp, at tc
Cal. temp, at te
Temp, change
23.00
22.80
22.80
22.60
22.50
22.40
0.20
0.20
22.59
22.50
0.09
Cal. temp, at te
Leaf temp, at tf
Temp, change
22.00
22.00
-5.00
27.00
-5.00
17.00
22.50
-5.00
17.50
22.40
-5.00
17.40
Sp. ht. dry leaves
.201
.194
.104
Wt. green leaves
Wt. dry leaves
Wt. total water
31.50
13.30
18.20
33.20
13.60
19.60
35.20
Wt. free water
H^O to be added
Total free water
10.80
11.24
0.00
0.10
10.80
Total bound water
% bound water
Average % bound
water
0.10
.151
40.70
11.00
12.20
24.20
28.50
17.92
18.43
0.00
0.00
11.34
17.92
18.43
7.40
8.26
6.28
9.97
40.66
42.14
38.53
35.00
41*40
36.76
31
TABLE III (Cont’d)
DATA ON BOUND WATER
Wt. tube & leaves
Wt. tube
Wt. leaves
A. eleeans
Sample Sample
one
two
82.60 104.50
61.20 80.90
21.40 23.60
L. dlvarlcata
Sample Sample
one
two
106.50 109.10
82.10 82.00
24.40 27.10
A. polycarpa
Sample Sample
one
two
84.50 103.40
61.10 80.80
23.40 22.60
Cal. temp, at tc
Cal. temp, at te
Temp, change
32.10
26.90
5.20
31.70
26.28
5.42
30.97
26.55
4.42
31.70
26.70
5.00
30.80
28.10
2.70
30.90
28.30
2.60
Cal. temp, at te
Leaf temp, at tf
Temp, change
26.90
-5.00
31.90
26.28
-5.00
31.28
26.55
-3.00
29.55
26.70
-3.00
29.70
28.10
-5.00
33.10
28.30
-5.00
33.30
Dish and dry leaves
Wt. dish
Wt. dry leaves
81.90
75.60
93.80
85.50
11.30
89.70
77.60
86.80
75.60
90.40
80.40
6.20
87.40
80.40
7.00
12.10
11.20
10.00
6.10
7.00
11.40
11.90
11.00
10.00
Cal. temp, at tc
Cal. temp, at te
Temp, change
30.65
30.40
0.25
30.50
30.20
0.30
31.00
30.50
0.50
31.10
30.60
0.50
30.65
30.10
0.55
30.48
30.10
0.38
Cal. temp, at te
Leaf temp, at tf
Temp, change
30.40
-5.00
35.40
30.80
-5.00
35.20
30.50
-5.00
35.50
30.60
-5.00
35.60
30.10
-5.00
35.10
30.10
-5.00
35.10
0.26
0.28
Wt. green leaves
Wt. dry leaves
Wt• total w$ter
81.40
24.40
11.30
13.10
27.10
23.40
22.60
12.10
15.00
11.20
12.20
10.00
15.20
23.60
7.00
16.60
Wt. free water
H^O to be added
Total free water
7.80
7.90
6.36
7.22
1.03
1.18
0.00
0.00
0.10
0.10
0.10
0.10
7.80
7.90
6.46
7.32
1.13
1.28
Total bound water
7.40
9.70
6.64
7.68
11.07
11.32
48.68
47.60
50.68
51.20
90.74
90.00
Dry leaves in tube
Sp. ht. dry leaves
% bound water
Average % bound
water
0.20
48*14
.318
.275
50.94
.263
.242
12.60
90.46
Introduction to Data on Rate of Drying. - The follow­
ing table gives'the weighings and calculations for each
determination at fifteen minute intervals extending over a
period of three hours.
The column giving the per cent of
water lost is based on the dry weight of the leaves, while
the next column uses the total weight of water as one hundred
per cent, designated 00.00
At the bottom of the page the results of the two
samples are added together and the average of the two Is
shown.
The curve for the average percentage of water lost
has been plotted (Figure l) for every plant used.
33
TABLE IV
DATA ON BATE OF DRYING
Sallx gooddingil
Sample one
Sample two
Dish & Grams Leaf % 3s0 Total % Dish & Grams Leaf % HgO Total %
leaves lost wt. lost fifeO lost leaves lost wt. lost HgO lost
00.00 14.1 00.00
89.8
88.9
0.90
0.80
0.60
0.40
0.50
0.50
88.1
87.5
87.1
86.6
86.1
0.20
85.9
85.5
84.8
84.4
0.40
0.70
0.40
13.2 16.98
12.4 15.09
11.8 11.32
11.4 7.55
10.9 9.44
10.4 9.44
10.2 3.77
9.8 7.55
9.1 13.21
8.7 7.55
00.00
10.22
9.09
6.82
4.54
5.68
5.68
2.27
4.54
7.95
7.54
92.6
91.5
91.0
90.5
89.8
89.1
88.7
88.4
88.1
87.8
87.5
00.00 12.2 00.00
1.10 11.1 23.91
0.50 10.6 10.87
0.50 10.1 10.87
0.70
0.70
0.40
0.30
0.30
0.30
0.30
9.4 15.22
8.7 15.22
8.3 8.70
8.0 6.52
7.7 6.52
7.4 6.52
7.1 6.52
00.00
14.47
6.58
6.58
9.21
9.21
5.26
3.95
3.95
3.95
3.95
Above sample dried at 1050 C.
3.4
81.0
Total
8.8
5.3 64.15
166.04
38.62
99.97
85.0
Total
2.5
7.6
11.3 54.35 26.90
165.21 100.09
Average % water lost, computed on dry leaf basis
16.98 15.09 11.32 7.55
9.44
2.5*91. ^ 8 2 IP^gZIfijgB J&uS£
)40.89 8£*gg 83*1888 J 7
20.44 12.98 11.0911.38
3d*&6
12.33
9.44
8,70
18,04
9.07
3.77 7.5 13.21
7.55
6.52 6.52 6.52
6.52
JSL£18 14.0719.75 14.07
5.14 7.03 9.86
7.07
Average % total water lost
10.22
14.47
)24_.26
12.34
9.09 6.82
4.54
5.68 5.68
6.58 6.58
9.21
9.21 5.26
15.62 15,,4a 15,7.
514^8.9 1 0 ^ 4
7.33 6.70 6.87 7.44 5.47
2.27
5.95
6 ,g£
3.10
4.54 7.95
5 •95 5.95
8.49 11.90
4.24 5.95
4.54
3«.95
8.49
4.24
34
TABLE IV (Cont'd)
DATA ON RATE OF DRYING
T.1 gnst.-riim -iflnnni eiim
Sample one
Sample two
Dish & Grams Leaf % HgO Total % Dish & Grams Leaf % HgO Total %
leaves lost wt. lost HgO lost leaves lost wt. lost HgO lost
o
o•
o
o
101.4
100.0
1.4
1.0
1.0
1.0
0.6
99.0
98.0
97.0
96.4
96.0
95.5
95.4
94.7
94.0
0.4
0.5
0.1
0.7
0.7
14.6 00.00
13.2 41.17
12.2 89.41
11.2 29.41
10.2 29.41
9.6 17.65
9.2 11.76
8.7 14.71
8.6 2.94
7.9 20.59
7.2 20.59
00.00
86.6
12.50
8.93
8.93
8.93
5.36
3.57
4.46
0.89
6.25
6.25
85.5
84.9
84.2
83.5
82.9
82.3
81.9
81.7
81.0
80.7
00.00 14.1 00.00
1.1 13.0 32.35
0.6 12.4 17.65
0.7
0.7
0.6
0.6
0.4
0.2
0.7
0.3
11.7 20.59
11.0 20.59
10.4 17.65
9.8 17.65
9.4 11.76
9.2 5.88
8.5 20.59
8.2 8.82
00.00
10.29
5.61
6.55
6.55
5.61
5.61
3.74
1.87
6.55
2.86
Above samples dried at 105° C.
3.8
90.2
Total 11.2
3.4 111.76 34.13
329.41100.21
4.8
75.9
Total 10.7
3.4 141.17 44.88
314.70100.11
Average % water lost, computed on dry leaf basis
41.17
32.55
373.52
36:76
29.41
17.65
47.06
23.53
29.41 29.41 17.65 11.76 14.71 2.94
20.59
1Z*6£ 3-7.65 11.76 5^88
50.00
50.0035.3029.4126.47 8.82
25.00 25.00 17.65 14.70 13.23 4.41
20.59 20.59
20.59 8.82
41.18 29.41
20.59 14.70
Average % total water lost
12.50
10.28
'122.78
11.39
8.83 .8.93- 8.95 5.36 3.57
5.61 6.55 6.55 5.61 5.61
14.5415.48 15.48 10.97 9.18
7.27 7.74 7.74 5.48 4.59
4.46
3.74
8.20
4.10
0.89 6.25 6.25
1.87 6.55 2.86
2.76 12.80 9.11
1.38 6.40 4.55
35
TABLE IV (Cont’d)
DATA ON RATE OF DRYING
Eucalyptus globulus ? Adult leaves
Sample one
Sample two
Dish & Grams Leaf % H20 Total % Dish & Grams Leaf % HoO .Total %
leaves lost wt . lost HgO lost leaves lost wt. lost HgO lost
101.6
101.1
00.00 26.0 00.00
1.5
0.7
0.9
1.3
99.4
98.5
97.2
96.2
96.1
95.7
95.2
94.8
94.2
1.0
0.1
0.4
0.5
0.4
0.6
25.5 12.60
23.8 5.88
22.9 7.56
21.6 10.92
20.6 8.40
20.5 0.84
20.1 3.36
19.6 4.20
19.2 3.36
18.6 5.04
. 00.00
10.64
4.96
6.38
9.22
7.09
0.71
2.84
3.54
2.84
4.25
101.9
100.2
99.4
98.5
98.2
97.5
97.3
96.8
96.5
96.1
95.8
00.00 21.6 00.00
00.00
19.9 16.66
19.1 7.84
18.2 8.82
17.9 2.94
17.2 6.86
17.0 1.96
16.5 4.90
16.2 2.94
15.8 8.92
15.5 2.94
14.91
7.02
7.90
2.63
6.14
1.75
4.39
2.63
3.51
2.63
1.7
0.8
0.9
0.3
0.7
0.2
0.5
0.3
0.4
0.3
Above samples dried at 105© C.
87.5
6.7
Total 14.1
11.9 56.38 47.50
118.48 99.97
90.5
5.3
Total 11.4
10.2 51.96 46.48
111.76 99.99
Average % water loss, computed on dry leaf basis
12.60
16.66
)29.26
14.63
5.88 7.55
7,84 ft.8g
13.7216.58
6.86 9.19
10.92 8.40 0.84
. ^ 9 4 6^,86 jUS6
13.86 15.26 2.80
6.93 7.63 1.40
3.36
4 ^9Q
8.26
4.13
4.20
2.94
7.14
3.57
3.36
3^92
7.28
2.64
5.04
2.94
7.98
3.99
Average % total water lost
10^64
14.91
)25.55
12,77
4.96 6.38 9.22
7.02 7.90 2_._63
11.981 4 ^ 8 11*85
5.99 7.14 5.92
7.09
6^14
13A£3
6.61
0.84
1.75
2.t46
1.23
3.36 4.20
4_,39 2^63
7 ^
6,2 2
3.61 30.8
3.36
3,51
6A5£
3.17
5.04
2.63
6,88
3.44
36
TABLE IV (Cont’d)
DATA ON RATE OF DRYING
Rorippa nasturitum-aauaticum
Sample one
Sample two
Dish & Grams Leaf % HgO Total % Dish & Grams Leaf % HgO Total %
leaves lost wt. lost HgO lost leaves lost wt. lost HgO lost
00.00 19.5 00.00
1.2 18.3 85.68
1.1 17.2 78.54
102.0
100.8
99.7
99.0
98.0
97.5
96.5
96.0
95.3
94.4
93.6
0.7
1.0
0.5
1.0
0.5
0.7
0.9
0.8
16.5
15.5
15.0
14.0
13.5
49.98
71.43
35.70
71.43
35.70
12.8 49.98
11.9 64.26
11.1 57.12
00.00
6.63
6.06
3.87
5.53
2.86
5.53
2.76
3.87
4.97
4.42
113.3
110.5
109.4
108.1
106.4
105.7
104.8
103.9
103.8
102.5
101.6
00.00 16.9 00.00
1.8 14.1280.0
1.1 13.0110.0
1.3
1.7
0.7
0.9
0.9
11.7130.0
10.0170.0
9.3 70.0
8.4 90.0
7.5 90.0
7.4 10.0
6.1130.0
5.2 90.0
0.1
1.3
0.9
00.00
17.61
6.92
8.18
10.69
4.40
5.66
5.66
0.63
8.17
5.66
Above samples dried at 105° C.
83,0
Total
9*7
8.1
1.4 692*86 53*59
1292.68 100.01
97*4
4.2
Total 15.90
1.0 420.0 26.42
1590.0 99.99
Average % water lost, computed on dry leaf basis
86.68 78.54
280,.00 3.0Q,%QQ
)365.66 188.54
182.84 94.27
49.98 71.43
JSQ,mSQ lELQSL
179.98241.43
89.99 120.71
35.70 71.43 35.70 49.98 64.26 57.12
10*00. .9DJ)D 3SLSSL XQ ..00 134.00 90.00
105.70 161.45 125.75 59.98 198.26 147.18
52.85 80.71 62.85 29.99 97.13 73.56
Average % total water lost
6.63
17.61
)24.24
12.12
6.08 3.87 5.53 2.76
6.92 8.18 10.69 4.40
13.00 18.05 16.82 7.16
6.50 6.08 8.11 3.53
5.53
5.66
11.19
4.21
2.76
5^66
8.48
4.21
3.87 4.97 4.42
.63 8.17 5.66
4.50 13.17 10.08
2.24 6.58 5.04
37 TABLE IV (Cont *d)
DATA ON RATE OF DRYING
Rlclnus fnmmnnla
Sample one
Sample •
two
Dish & Grams Leaf % Ho0 Total % Dish & Grams Leaf % HoO Total %
HgO lost
leaves lost wt. lost HgO lost leaves lost wt. lost :
104.4
102.8
101.9
100.9
99.a
99.1
98.1
97.4
96.5
95.8
95.1
00.00 17.6 00.00
00.00
36.35
20.45
22.72
24.99
15.90
22.72
15.90
15.90
20.45
15.90
12.13
6.82
7.58
8.33
5.30
7.58
5.30
6.82
5.30
5.30
1.6
0.9
1.0
1.1
0.7
1.0
0.7
0.7
0.9
0.7
16.0
15.1
14.1
13.0
12.3
11.3
10.6
9.0
9.7
8.3
00.00 23.1
95.6
94.0
93.0
91.9
90.7
90.0
89.6
88.7
88.1
87.4
86.4
1.6
1.0
1.1
1.2
0.7
0.4
0.9
0.6
0.7
1.0
21.5
20.5
19.4
18.2
17.5
17.1
16.2
15.6
14.9
13.9
00.00 00.00
27.12
16.95
18.65
20.34
11.87
6.78
15.26
10.17
11.87
16.95
9.30
5.80
6.40
6.98
4.07
2.33
5.23
3.59
4.07
5.82
Above samples dried at 1050 c.
3.9
91.2
Total 13.2
4.4 88.64 29.54
300.00 100.00
78.4
Total
8.0
17.2
5.9 135.39 46.51
291.53100.10
Average % water lost, computed on dry leaf basis
36.35
27.13
>63.47
21.73
SO.45
16.95
37.40
18.70
23.72 S4.99
18.65 30.34
40.37 45.33
20.68,22.66
15.90
11.87
27.77
13.88
3S.7S
..§.,2g.
29.50
14.75
15.90 20.45
1£_,25
51.16 30.63
15.58 15.31
15.90
11,87
37.77
13.88
15.90
16,96
32.85
16.42
Average % total water lost
12.13
6.82 7.58 8.53 5.30
9.30
5.80 6.40 6.98 4.07
>21.43 13.62 15.98 15.31 9.5.7
10.71
6.31 6.99 7.65 4.68
7.58
2.53
5.30 6.82 5.30
5.33 3.59 4.07
IPjiSS IQjJA 9.37.
4.95
5.26 5.20 4.68
5.30
5,82
11^1.2
5.56
38
TABLE IV (Contfd)
DATA ON RATE OF DRYING
Larrea divaricata
Sample one
Sample two
Dish & Grams Leaf % Ho0 Total % Dish & Grams Leaf % Ho0 Total %
leaves lost wt. loft H^O lost leaves lost wt. lost HgO lost
0.4
0.3
0.4
0.3
11.7 00.00
11.3 5.72
11.0 4.29
10.6 5.72
10.3 4.29
0.2
10.1
2.86
0.3
9.8
9.6
9.5
9.4
9.2
4.29
o
o•
o
o
93.7
93.3
93.0
92.6
92.3
92.1
91.8
91.6
91.5
91.4
91.2
0.2
0.1
0.1
0.2
2.86
1.42
1.42
2.86
00.00
8.51
6.38
8.51
6.38
4.26
6.38
4.26
2.13
2.13
4.26
98.1
97.6
97.2
96.9
96.6
96.3
96.0
95.8
95.7
95.5
95.3
00.00 12.9 00.00
00.00
12.4
9.90
7.92
5.94
5.94
5.94
5.94
3.96
1.98
3.96
3.96
0.5
0.4
0.3
0.3
0.3
0.3
12.0
11.7
11.4
11.1
10.8
10.6
0.2
0.1
0.2
0.2
10.5
10.3
10.1
6.41
5.13
3.85
3.85
3.85
3.85
2.56
1.28
2.56
2.56
Above samples dried at 1050 c.
89.0
Total
2.2
4.7
7.0 31.46 46.82
67.19 100.02
93.0
Total
2.3
5.1
7.8 29.49 45.54
65.38 100.98
on dry leaf basis
5.72 *4.29
6.41 5,15
1 2 1-3 9.42
6.06 4.71
) .
5.72
^85
9,5,7
4.78
4.29
5.85
8jtl4
4.07
2.86
3*85
£*21
3.35
4.29
&*£&
8.14
4.07
2.86
§jt4&
2.71
2.86
1.42
J-.2S
3,70
1.35
1.42
2.56
,3ji98
1.99
2.13
1.98
4,11
2.05
2.13 4.26
5.96 5.96
6^09 8,22
3.04 4.11
2.56
5.42
2.71
Average % total water lost
8.51
9f90
)18.41
9.20
6.38 8.51
7.92 5.94
14.30 14.45
7.15 7.22
6.38
4.26 6.38 4.26
5.94
5.94 5.94 5.96
12.52 10.20 12.52 . 8 tgg
6.16
5.10 6.11 4.11
39
TABLE IV (ContM)
DATA ON RATE OF DRYING
Eucalyptus globulus. Juvenile leaves
Sample one
Sample two
Dish & Grams Leaf % HpG Total % Dish & Grams Leaf % HpO Total %
leaves lost wt. loft HgO lost leaves lost wt. loft HgO lost
o
o
•
o
o
96*4
95.6
94.3
94.1
93.9
93.5
93.0
92.7
92.4
92.0
91.6
0.8
1*3
0.2
0.2
0.4
0.5
0.3
0.3
0.4
0.4
14.1 00.00
13.3 19.05
12.0 30.95
11.8 4,76
11.6 4.76
11.2 9.52
10.7 11.90
10.4 7.14
10.1 7.14
9.7 9.52
9.3 9.52
00.00
8.08
13.13
2.02
2.02
4.04
5.05
3.03
3.03
4.04
4.04
108.0
107.2
106.2
106.2
105.9
105.6
105.1
104.8
104.5
104.3
104.0
00.00 11.6 00.00
0.8 10.8 21.62
9.8 27.03
1.0
9.8 0.00
0,0
0.3
9.5 8.11
0.3
9.2 8.11
0.5
0.3
8.7 13.51
8.4 8.11
0.2
0.2
8.1
8.11
7.9
7.6
5.40
0.3
8.11
00.00
10.13
12.66
0.00
3.80
3.80
6.33
3.80
3.80
2.53
3.80
Above samples dried at 105° C.
86.5
Total
5.1
9.9
4.2 121.40 51.51
235.71 99.99
100.0
Total
3.9
7.9
3.7 105.41 49.37
213.51 100.02
Average % water lost, computed on dry leaf basis
19.05
21*62
)i2*§Z
20.35
30.95
£1*03
57.98
28.99
4.76 4.76 9.52
0*00 8*11 8 * H
4.76 13.87 17.65
2.38 6.42 8.81
11.90
13.51
85.41
12.70
7.14 7.14 9.52 9.52
8.11 8.11 5.40 8.11
15.25 15.25 14.92 17.63
7.62 7.62 7.46 8.81
Average % total water lost
8.08
10.13
)18.21
9.10
13.13
12.66
85.79
12.89
2.02
0.00
2.02
1.01
2.02
3.80
5.82
2.91
4.04 5.05
3.80 6.33
7.84 11.38
3.92 5.69
3.03
3.80
6.83
3.41
3.03
3.80
6.83
3.41
4.04
3.53
6.57
3.28
4.04
3.80
7^86
3.92
40
TABLE IV (Cont»d)
DATA ON RATE OF DRYING
Amaranthus palmer!
Sample one
Sample two
Dish & Grams Leaf % HoO Total % Dish & Grams Leaf % HgO Total %
leaves lost wt. lost HgO lost leaves lost wt. lost HgO lost
100.7
00.00 18.2 00.00
00.00
17.5
16.5
16.0
14.8
14.5
13.9
13.2
5.43
7.75
3.88
9.30
2 .33
4.65
5.43
3.10
3.10
5.43
100.0
0.7
99.0
98.5
97.3
97.0
96.4
95.7
95.3
94.9
94.2
1.0
0.5
1.2
0.3
0.6
0.7
0.4
0.4
0.7
13.21
18.88
9.44
22.64
5.66
11.32
13.21
12.8 7.55
12.4 7.55
11.7 13.21
112.3
111.3
110.5
109.8
108.8
107.8
107.2
106.6
106.0
105.0
104.6
00.00 15.8 00.00
1.0 14.8 21.74
0.8 14.0 17.39
0.7
13.3
12.3
11.3
10.7
1.0
1.0
0.6
0.6
0.6
1.0
10.1
9.5
8.5
7.1
0.4
15.22
21.74
21.74
13.04
13.04
13.04
21.74
8.69
00.00
8.93
7.34
6.25
8.93
8.93
5.36
5.36
5.36
8.93
3.57
Above samples dried at 105° C.
6.4
87.8
Total 12.9
5.3 120.75 49.61
243.40 100.00
101.1
3.5
Total
11.2
4.6
76.09 31.25
243.47 100.21
Average % water lost, computed on dry leaf basis
13.21
21.74
)54.95
17.47
18.11 9.44 22.64
5.66
.
17.^39 15^22 SJU74 2.1^24
56.27 24.66 44.38 27.40
18.15 12.55 22.55 15.70
11.32
13,04
24.56
12.18
13.21 7.55 7.55 13.21
l ^ .Q.4 15,04 21.74 8.6,9
26.25 20.59 29.29 21.90
15.12 10.29 14.64 10.95
Average % total water lost
5.45
8.93
)14.36
7.18
7.75 5.88
9.50 2.35 4.65 5.43
7.54 6.25
8.93 8.93 5.36 5.36
15.0910.13 18.85 11.26 10.01 10.79
7.54 5.06
9.16 5.63 5.00 5.39
5.10 3.10 5.43
5.36 8.93 3.57
8.46 12.03 .9w00
4.23 6.01 4.50
41
TABLE IV (Cont’d)
DATA ON RATE OF DRYING
Populns fremontii
Sample one
Sample two
Dish & Grams Leaf % HpO Total % Dish & Grams Leaf % HpO Total %
leaves lost wt. lost HgO lost leaves lost wt. lost HgO lost
00.00 18.4 00.00
100.8
0.4
1.4
0.4
0.9
0.4
0.4
0.4
0.5
0.5
0.3
100.4
99.0
98.6
97.7
97.3
96.9
96.5
96.0
95.5
95.2
18.0 6.35
16.6 22.22
16.2 6.35
15.3 14.28
14.9 6.35
14.5 6.35
14.1 6.35
13.6 7.94
13.1 7.94
12.8 4.76
00.00
3.31
11.57
3.31
7.44
3.31
3.31
3.31
4.13
4.13
2.48
93.6
92.8
91.9
91.4
90.6
90.0
89.6
89.3
88.8
88.2
87.9
00.00 16.0 00.00
0.8 15.2 14.81
0.4
0.3
0.5
14.3 16.61
13.8 9.26
13.0 14.81
12.4 11.11
12.0 7.40
11.7 5.56
11.2 9.26
0.6
10.6 11.11
0.3
10.3
0.9
0.5
0.8
0.6
5.56
00.00
7.55
8.49
4.72
7.55
5.66
3.77
2.83
4.72
5.66
2.83
Above samples dried at 105° C.
88.7
6.5
Total 12.1
6.3 103.17 53.71
192.06 99.91
83.0
4.9
Total 10.6
5.4
90.75 46.22
196.29 99.98
Average % water lost, computed on dry leaf basis
6.35 22.22 6.3514.28
6.35 6.35 6.35
14.81 16.61 9,^6 14*81 JULJUL Z»4£ 5^5,6.
-)21.16 38.85 15^61 29.09 17.46 15.75 jJUSl
10.58 19.41 7.8014.54
8.73 6.87 5.95
7.94 7.94 4.76
9^26 11.11 5.56
19-^6 10*32
8.60 9.52 5.16
Average % total water lost
3.31
7.55
)10.85
5.42
11.57
8.49
20.06
10.03
3.31
4.72
8.05
4.01
7.44
7.55
14.99
7.49
3.31
5.66
8.97
4.48
3.31
5.77
7.08
3.54
3.31
2.85
6.14
3.07
4.13
4.72
8.85
4.42
4.13 2.48
5.66 2.85
9.79 5.51
4.89 2.65
42
TABLE IV (Cont'd)
DATA ON RATE OF DRYING
Medicaeo sativa
Sample one
Sample two
00.00
1.0
1.0
0.8
96.4
95.4
94.4
93.6
92.9
92.2
91.1
90.9
90.0
89.2
88.5
0.7
0.7
1.1
0.2
0.9
0.8
0.7
20.8 00.00
00.00
19.23
19.23
15.38
13.46
13.46
21.15
3.85
17.31
15.38
13.46
6.41
6.41
5.13
4.49
4.49
7.05
1.28
5.77
5.13
4.49
19.8
18.8
18.0
17.3
16.6
15.5
15.3
14.4
13.6
12.9
95.5
94.4
93.7
92.4
92.2
91.5
90.7
90.1
89.8
88.7
o
o
.
o
o
Dish & Grams Leaf % E^0 Total % Dish & Grams Leaf % H«0 Total %
leaves lost wt. lOot HgO lost leaves lost wt. lost HgO lost
1.1
8.2
88.2
0.5
7.7
1.1
0.7
1.3
0.2
15.0
13.9
13.2
11.9
11.7
11.0
10.2
0.7
0.8
0.6
9.6
9.3
0.3
00.00
00.00
30.55
19.33
35.87
5.52
19.33
22.09
16.57
8.28
30.55
13.80
9.65
6.14
11.40
1.75
6.14
7.02
5.26
2.63
9.65
4.39
Above samples dried at 105° C.
7.7
80.8
Total 15.6
5.2 148.01 49.36
300.00 100.01
84.1
Total
4.1
11.4
3.6 113.9
35.96
316.66I 99.99
Average % water lost, computed on dry leaf basis
19.S3 19.23
15.38 13.46
30.55 19.35 35.87 5.52
^49.78 38.56
51.25 18.98
24.89 19.2825.62
9.49
13.46
19.33
32.79
16.39
21.15 3.85 17.31 15.38
22.09 16.57 8.28 30.55
45.24 20.42 25.59 45.95
21.62 10.21 12.79 23.86
13.46
13.80
27.26
13.63
Average % total water lost
6.41
9.65
)16.06
8.03
6.41 5.13
6.14 11.40
13.55 16.53
6.27 8.26
4.49 4.49 7.05
1.75 6.14 7.03
6.24 10.63 14.07
3.12 5.13 7.03
1.28
5.36
6.54
3.27
5.77 5.13 4.49
2.63 9.65 4.39
8.40 14.78 8.88
4.20 7.39 4.44
43
TABLE IV (Cont'd)
DATA ON RATE OF DRYING
Bursera microphvlla
Sample one
Sample two
Dish & Grams Leaf % IL0 Total % Dish & Grams Leaf % HU0 Total %
leaves lost wt. lost HgO lost leaves lost wt. lost HgO lost
00.00 14.6 00.00
0.6 14.0 13.04
90.2
89.6
89.2
88.5
0.4
0.7
0.4
0.5
0.4
0.5
88.1
87.6
87.2
86.7
0.6
0.6
86.1
85.5
85.2
0.3
13.6 8.70
12.9 15.22
12.5 8.70
12.0 10.87
11.6 8.70
11.1 10.87
10.5 13.04
9.9 13.04
9.6 6.5
00.00
60.00
40.00
70.00
40.00
50.00
40.00
50.00
60.00
60.00
30.00
92.4
91.5
91.3
90.0
90.2
89.8
89.2
88.6
88.1
87.8
87.3
00.00 12.0 00.00
0.9 11.1 24.99
0.2 10.9 5.55
0.4 10.5 11.11
0.7
0.4
0.6
0.6
0.5
0.3
0.5
9.8 19.44
9.4 11.11
8.8 16.66
8.2 16.66
7.7 13.88
7.4 8.33
6.9 13.88
00.00
10.35
2.30
4.60
8.05
4.60
6.90
6.90
5.75
3.45
5.75
Above samples dried at 105° C.
80.2
5.0
Total 10.00
4.6 108.70
217.39
50.00 85.7
100.00 Total
3.6
8.7
3.3
91.66 41.38
233.33 100.03
Average % water lost, computed on dry leaf basis
13.04
24.99
^38.05
19.01
8.70 15.22
8.70 10.87 8.70
5.55 11.11 19.44 11.11 16.66
14.2526.55 28.14 21.98 25.56
7.12 13.16 14.07 10.99 12.68
10.87
16.66
27.53
13.76
13.04 13.04 6.50
13.88 8.55 15.88
26.92 21.57 20.58
13.46 10.68 10.19
Average % total water lost
6.00
10.55
)16.35
8.17
4.00 7.00 4.00
2.50 4.60 8.05
6.50 11.60 12.05
3.15 5.80 6.02
5.00 4.00
5.00 6.00 6.00 3.00
4.60 6.90
6.90 5.75 5.45 5.75
9,60
U *9Q lit.75 9^4$, 8,75
4.80 5.45
5.95 5.87 4.72 4.37
44
TABLE XV (Contfd)
DATA ON RATE OF DRYING
Atriolex eleeans
Sample one
Sample two
Dish & Grams Leaf % HpO Total % Dish & Grams Leaf % HpO Total %
leaves lost wt. lost HgO lost leaves lost wt. lost HgO lost
o
o•
o
o
95.4
94.7
93.9
93.2
93.0
92.4
91.7
90.9
90.3
90.0
89.1
0.7
0.8
0.7
0.2
0.6
0.7
0.8
0.6
0.3
0.9
19.7
19.0
18.2
17.5
17.3
16.7
16.0
15.2
14.6
14.3
13.4
00.00
00.00
10.29
11.76
10.29
2.94
8.82
10.29
11.76
8.82
4.41
13.23
5.43
6.20
5.43
1.55
4.65
5.43
6.20
4.65
2 .32
6.98
94.5
93.8
93.3
92.9
92.4
92.0
91.4
90.7
90.1
89.6
88.8
00.00 13.9 00.00
0.7
0.5
0.4
0.5
0.4
0.6
0.7
0.6
0.5
0.8
13.2 15.22
12.7 10.87
12.3 8.70
11.8 10.87
11.4 8.70
10.8 13.04
10.1 15.22
9.5 13.04
9.0 10.87
8.2 17.39
00.00
7.53
5.37
4.30
5.37
4.30
6.45
7.53
6.45
5.37
8.60
Above samples dried at 105° C
82.5
6.6
Total 12.9
6.8
97.06 51.15
189.70 99.99
85.2
Total
3.6
9.3
4.6
78.26 38.70
202.17 99.97
Average % water lost, computed on dry leaf basis
10.29
15.22
)25.51
12.75
11.76 10.29 2.94 8.82 10.29
10.87 8.70 10.87 8.70 15.04
22.65
18.9913.81 17.52 23.53
11.31
9.49 6.90 8.76 11.66
11.76 8.82 4.41 13.23
15.22 15.04 10.87 17.39
26.98 21.86 15.28 50.62
13.49 10.93 7.64 15.31
Average % total water lost
5.43
7.55
>12*98
6.48
6.20
5.57
11.57
5.78
5.43
4 m5,a
9.75
4.86
1.55
5.37
6.92
3.46
4.65
4A5Q
8.95
4.47
5.43
6.20 4.65
2*53 6*4.
5
11.88 15.73 11.10
5.94 6.86 5.55
£*45
2.32
5.37
7.69
3.84
6.98
8.60
15.58
7.79
45
TABLE IV (Contfd)
DATA ON RATE OF DRYING
Prosopis chilensis
Sample one
Sample two
Dish & Grams Leaf % BU0 Total % Dish & Grams Leaf % H_0 Total %
leaves lost wt. lost BgQ lost leaves lost wt. lo§t HgO lost
00.00
1.1
0.7
0.6
0.9
1.2
0.6
0.4
0.7
0.4
0.6
115.1
114.0
113.3
112.7
111.8
110.6
110.0
109.6
108.9
108.5
107.9
32.6 00.00
31.5 7.48
30.8 4.76
30.2 4.08
29.3 6.12
28..1 8.16
27.5 4.08
27.1 2.72
26.4 -4.76
26.0 2.72
25.4 4.08
00.00
6.15
3.91
3.35
5.03
6.70
3.35
2.23
3.91
2.24
3.35
106.3
105.2
104.3
103.4
102.5
101.6
101.2
100.8
100.0
99.6
98.7
00.00
1.1
0.9
0.9
0.9
0.9
0.4
0.4
0.8
0.4
0.9
28.7 00.00
27.6 9.02
26.7 7.37
25.8 7.37
24.9 7.37
24.0 7.37
23.6 3.27
23.2 3.27
22.4 6.55
22.0 3.27
21.1 7.37
00.00
6.66
5.46
5.46
5.46
5.46
2 .42
2.42
4.85
2.42
5.46
Above samples dried at 105° C.
97.2
Total
10.7
17.9
14.7
72.80 59.78
121.77 99.91
89.8
8.9
Total 16.5
12.2
72.95 55.94
135.24 100.10
Average % water lost, computed on dry leaf basis
4.76 4.08 6.12 8.16
7,>52 2*32 2*32 7*32
)16.50 12.13 11*15 13.*49 1£*53
8.25 6.06 5.72 6.79 7.76
7.48
4.08
5.27
7.55
3.67
2.72 4.76
3.27 6.55
5.99 11.51
2.99 5.65
2.72 4.08
5.27 7^52
5.99 11.45
2.99 5.72
Average % total water lost
6.15
6.66
)12.81
6.40
3.91
5.46
9.57
4.68
3.35 5.03 6.70
5.4& 5.46 5.46
8.81 10.49 12.J.6
4.40 5.24 6.08
3.35
2.42
5*22
2.88
2.23
2.42
4*6&
2.32
3.91
4.85
8*26
4.38
2.24
2,4.^
4*65
2.32
3.35
5 *46
8*81
4.40
46
TABLE IV (Cont,d)
DATA ON RATE OF DRYING
Salsoli kali
Sample one
Sample two
Dish & Grams Leaf % HpO Total % Dish & Grams. Leaf % HpO Total %
leaves lost wt. lost HgO lost leaves lost wt. lost HgO lost
o
o•
o
o
109.0
107.8
106.5
105.5
105.0
104.2
103.2
102.5
101.4
100.6
99.3
1.2
1.3
1.0
0.5
0.8
1.0
0.7
1.1
0.8
1.3
26.5
25.3
24.0
23.0
22.5
21.7
20.7
20.0
18.9
18.1
16.8
00.00
19.36
20.97
16.13
8.07
12.90
16.13
11.29
17.74
12.90
20.97
00.00
5.91
6.40
4.93
2.46
3.94
4.93
3.45
5.42
3.94
6.40
100.7
99.7
98.8
97.8
97.0
96.0
95.1
94.1
92.9
91.9
90.6
00.00
1.0
0.9
1.0
0.8
1.0
0.9
1.0
1.2
1.0
1.3
23.1
22.1
21.2
20.2
19.4
18.4
17.5
16.5
15.3
14.3
13.0
00.00
19.23
17.31
19.23
15.38
19.23
17.31
19.23
23.07
19.23
25.00
00.00
5.59
5.03
5.59
4.47
5.59
5.03
5.59
6.70
5.59
7.26
Above samples, dried at 105° C.
88.7 10.6
Total 20.3
6.2 107.98 52.22
327.42 99.99
82.8
7.8
Total 17.9
5.2 149.99 43.67
344.23 100.10
Average % water lost, computed on dry leaf basis
19*36
19.23
)38.59
19.29
20*97
17.51
38.28
19.14
16*13
19.25
35.36
17.68
8.07
15.58
25.45
11.72
12.90
19.23
32.13
16.06
16.13
17.51
53.54
16.72
11.29
19.23
50.52
15.26
17.74
25.07
40.81
20.40
12.90 20.97
19.25 25.00
52.15 45.97
16.06 22.98
4.93 3.45
5.42
gu?P.
3.94 6.40
5^59 7_._26
4.98 4.52
6.06
4.76 6.83
Average % total water lost
5.91 6.40
v 5.59 . 5.03
4.93
.5,59
2.46 3.94
4»4Z
)n*5o 11.45 ifiuss
s^aa a ^ a
5.75
5.71
5.26
3.46 4.76
9^53 15.ee
47
TABLE IV (Cont fd)
DATA ON RATE OF DRYING
Atriplex polvcarpa
Sample one
Sample two
Dish & Grams Leaf % BU0 Total % Dish & Grams Leaf % H~0 Total %
HgO lost leaves lost wt . lost HgO lost
leaves lost wt . lost ;
o
o•
'o
o
94.7
93.8
93.4
93.0
92.4
92.0
91.5
91.0
90.7
90.3
90.1
0.9
0.4
0.4
0.6
0.4
0.5
0.5
0.3
0.4
0.2
19.0
18.1
17.7
17.3
16.7
16.3
15.8
15.3
15.0
14.6
14.4
00.00
9.89
4.40
4.40
6.59
4.40
5.50
5.50
3.30
4.40
2.20
00.00
9.09
4.04
4.04
6.06
4.04
5.05
5.05
3.03
4.04
2.02
109.9
109.4
108.6
107.8
107.0
106.8
106.2
105.9
105.6
105.2
104.2
00.00
0.5
0.8
0.8
0.8
0.2
0.6
0.3
0.3
0.4
1.0
29.5 00.00
29.0 3.40
28.2 5.75
27.4 5.75
26.6 5.75
26.4 1.44
25.8 4.31
25.5 2.16
25.2 2.16
24.8 2.88
23.8 7.19
00.00
3.21
5.13
5.13
5.13
1.28
3.85
1.97
1.97
2.56
6.41
Above samples dried at 105° C.
84.8
Total
5.3 9.1
58.24
9.9
108.78
53.53
99.99
94.3
9.9
Total 15.6
13.9
70.50 63.50
112.23 100.10
on dry leaf basis
9.89
3,40
)15,29
6.64
4.40 4.40
6.59 4.40
5.75 5.75
5.75 1*40
10.15JlCUIS 1&.54 A M
5.07 5.07
6.17 2.92
5.50
£*31
9*81
4.90
5.50
2^.6
1*66
3.82
3.30
2tl6
5.46
2.73
4.40
§*88
7.28
3.64
2 •20
7.X9
9 f39
4.69
3.03
1*97
5.00
2.50
4.04
2.56
6.60
3.30
2.02
6.41
8.43
4.21
Average % total water lost
9.09
3*£1
)ia*30
6.15
4.04
5.13
9.17
4.58
4.04
5*13
6.06
5.15
4.04
5.05
XjlS.8
5*8£
9*12 1109
5.32
2.66
8.90
4.45
4.58
5.59
5.05
1*S2
7.02
3.51
48
TABLE IV (Cont fd)
DATA ON HATE OF DRYING
Olneva tesota
Dish & Grams Leaf % HpO Total % Dish & Grams Leaf % Hp0 Total %
leaves lost wt. lost HgO lost leaves lost wt. lost HgO lost
00.00
0.5
0.3
0.5
0.5
0.3
0.3
0.4
0.5
0.5
93.8
93.3
93.0
92.5
92.0
91.7
91.4
91.0
90.0
89.5
17.7
17.2
16.9
16.5
15.9
15.6
15.3
14.9
13.9
13.4
00.00
5.50
3.30
5.50
5.50
3.30
3.30
4.40
5.50
5.50
91.6 00.00
91.3
0.3
90.9 . 0.4
0.4
90.5
0.4
90.1
89.8
0.3
0.3
89.5
0.4
89.1
0.5
88.2
0.5
87.7
00.00
5.82
3.49
5.81
5.81
3.49
3.49
4.65
5.81
5.81
13.7 00.00
13.4 5.36
13.0 7.14
12.6 7.14
12.2 7.14
11.9 5.36
11.6 5.36
11.2 7.14
10.3 8.93
9.8 8.93
00.00
3.70
4.94
4.94
4.94
3.70
3.70
4.94
6.17
6.17
Above dried samples dried at 105° C.
85.2
Total
4.5 9.1
8.6
47.26
94*56
49.99
99.99
85.5
Total
4.2
8*1
5.6
75.00 51.98
144.64 99.99
Average % water lost, computed on dry leaf basis
5.50
5.56
)10.86
5.43
3.30 5.50 5.50 3.30
7^24 7^14 .7.,M 5,56
10.4412.64 12.64 8^66
5.22 6.32 6.32 4.33
3.30
5,36
8.66
4.33
4.40 5.50 5.50 5.50
7.14 7.14 8.93 8.95
11.5412.64 14.43 14.45
5.77 .6.32 7.21 7.21
Average % total water lost
5.81
3.70
>9,51
4.75
3.49 5.81 5.81 3.49
4.94 4._94 4.94 3.J7Q
8.45 10.75 10.75 7.19
4.21 5.37 5.37 3.59
3.49
5.70
7.19
3.59
4.65 5.81 5.81 5.81
4.94 4.94 6 ^ 2
9.59 10.75 11.98 11.98
4.79 5.37 5.99 5.99
CHAPTER V
- INTERPRETATION OF DATA
An examination of the data on osmotic pressure in
Table V reveals a wide range of osmotic pressures among
plants occurring in correspondingly widely varied habitats.
Likewise a study of bound water shows marked varia­
tions in quantities (Table VI).
Incipient Transpiration and Rate of Drying. - The
result of the first weighing which gives the incipient
transpiration showed Olneva tesota to have lost the least,
and the adult leaves of Eucalyptus globulus to have lost the
greatest amount of water.
These plants were almost the ex­
tremes throughout the entire experiment on the rate of dry­
ing.
Salix gooddingii lost slightly more after the first
weighing than the adult leaves of Eucalyptus.
The relative places of the plants are given in Table
VIII, the plants being arranged according to the amounts of
water lost at the end of the first weighing.
A study of
the graphs (Figure l) shows that after the first weighing
the plants tended to fall into two groups, and at the fourth
weighing three groups were evident.
The relative positions
were not maintained throughout the drying process.
Some
evident changes were made by Bursera microphvlla at the second
weighing and by Medicago sativa at the third weighing, as well
as the juvenile leaves of Eucalyptus globulus at the fourth
weighing.
Continued drying caused changes which should not be
considered with too much concern due to the death or near
death of the protoplasm, and other factors which influence
the loss of water, such as respiration and the closing of
the stomata*
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51
TABLE V
PLANTS ARRANGED ACCORDING TO OSMOTIC PRESSURE
Rorippa nasturtium-aquaticum
Eucalyptus globulus,juvenile leaves
9.403 atmospheres
11.£86
atmospheres
Bursera microphylla
11.698 atmospheres
Salix gooddingii
14.073 atmospheres
Medicago sativa
14.68
Eucalyptus globulus,
adultleaves
atmospheres
15.436 atmospheres
Amaranthus palmer!
17.722 atmospheres
Ricinus communis
18.668 atmospheres
Populus fremontii
19.52
Salsola kali
19.886 atmospheres
Prosopis chilensis
£0.48
atmospheres
Ligustrum japonicum
£2.06
atmospheres
Olneya tesota
££.56
atmospheres
Larrea divaricata
£8.267 atmospheres
Atriplex elegans
49.53
Atriplex polycarpa
66.928 atmospheres
atmospheres
atmospheres
52
TABLE VI
PLANTS ARRANGED ACCORDING TO PER CENT OF BOUND WATER
Salsola kali
15.22
Bursera microphylla
19.70
Ligustrum japonicum
21.46
Populus fremontii
21.77
Medicago sativa
25.04
Rorippa nasturtium-aquaticum
25.50
Salix gooddingii
26.06
Olneya tesota
26.21
Amaranthus palmer!
27.38
Prosopis chilensis
27.67
Ricinus communis
29.72
Eucalyptus globulus
juvenile leaves
36.76
Eucalyptus globulus
adult leaves
41.40
Atriplex elegans
48.14
Larrea divaricata
50.94
Atriplex polycarpa
90.37
TABLE VII
PLANTS ARRANGED ACCORDING TO MOISTURE PERCENTAGE
BASED ON DRY LEAF WEIGHT
Rorippa nasturtium-aquaticum
1441.43
Salsola kali
335.82
Ligustrum japonicum
322.05
Medicago sativa
308.50
Ricinus communis
295«76
Amaranthus palmeri
243.43
Bursera microphylla
225.36
Eucalyptus globulus
juvenile leaves
224.61
Atriplex elegans
195.97
Populus fremontii
194.17
Salix gooddingii
164.66
Prosopis chilensis
128.50
Olneya tesota
119.58
Eucalyptus globulus
adult leaves
115.12
Atriplex polycarpa
110.01
Larrea divaricata
66*28
TABLE VIII
RELATIVE POSITION OF EACH SPECIES DETERMINED
BY ITS INCIPIENT TRANSPIRATION, (COLUMN l)
AND SUBSEQUENT POSITIONS (COLUMNS 2,3,4,5)
AS DESICCATION CONTINUED
Species
Eucalyptus globulus
adult leaves
Salix gooddingii
Rorippa nasturtiumaquaticum
Ligustrum japonicum
Ricinus communis
Larrea divaricata
Eucalyptus globulus
juvenile leaves
Bur sera microphylla
Medicago sativa
Amaranthus palmeri
Atriplex elegans
Prosopis chilensis
Atriplex polycarpa
Salsola kali
Populus fremontii
Olneya tesota
Weighing Sequences
3
4
5
Average
Place
1 2
1
3
4
4
3
3
2
2
1
2
1
1
3
4
5
6
7
5
4
6
7
1
2
3
5
6
7
3
1
5
6
9
4
2
5
6
10
4
2
5
6
7
8
9
10
11
12
13
14
15
16
13
10
9
11
14
15
12
8
16
11
8
9
12
14
15
13
10
16
11
10
7
14
13
12
15
8
16
11
9
7
13
12
15
14
8
16
11
10
8
12
13
15
14
9
16
55
TABLE IX
TOTAL PER CENT OP WATER LOST AFTER EACH WEIGHING
PLANTS ARRANGED ACCORDING TO GREATEST LOSS AT FIRST WEIGHING
Species
1
Eucalyptus
globulus,
adult leaves
Salix
gooddingii
Rorippa
nasturtium
Ligustrum
japonicum
Ricinus
communis
Larrea
divaricata
Eucalyptus
globulus,
juvenile
leaves
Bursera
microphylla
Medicago
sativa
Amaranthus
palmeri
Atriplex
elegans
Prosopis
chilensis
Atriplex
polycarpa
Salsola kali
Populus
fremontii
Olneya tesota
2
Weighing Sequences
3
4
5
6
7
8
IS *77 18.76 25.90 31.82 38.43 39.66 43.27 46.35
12.54 20.17 26.87 33.74 41.18 46.15 49.75 53.99
12.12 18.62 24.64 32.75 36.33 41.92 46.13 48.39
11.39 18.66 26.40 34.14 39.62 44.21 48.31 49.69
10.71 17.03 24.01 31.57 36.25 41.20 46.47 51.60
9.21 16.36 23.58 29.75 34.84 41.01 45.11 47.17
9.10 21.99 23.00 25.91 29.83 35.52 38.93 42.34
8.17 11.32 17.12 23.14 27.94 33.39 39.34 45.21
8.03 14.30 22.57 25.69 31.00 38.04 41.31 45.51
7.17 14.72 19.78 28.94 34.57 39.57 44.96 49.19
6.48 12.26 17.12 20.58 25.05 30.99 37.85 43.40
6.40 11.08 15.48 20.72 26.80 29.68 32.00 36.38
6.15 10.73 15.31 20.90 23.56 28.01 31.52 34.02
5.75 11.46 16.72 20.19 24.95 29.92 34.44 40.50
5.42 15.45 19.46 26.95 31.43 35.07 38.04 42.66
4.76
8.97 14.35 19.72 23.32 26.92 31.71 37.09
CHAPTER VI
DISCUSSION
The Significance of Osmotic Pressure. - A fundamental
need of all organisms in order to survive is water.
The in­
take of water of all cells is due to the cell content main­
taining a higher osmotic pressure than that of the surround­
ing medium.
In this discussion the word osmosis will be
understood to mean the passage of water molecules through a
semi-, or differentially permeable membrane from a place
where those molecules are high in concentration to the side
where those molecules are of a lower concentration.
If
water is to pass into a cell the concentration of water mole­
cules outside the cell must be greater than the concentra­
tion on the inside.
The reverse is also true;
that is, if
the concentration of water molecules on the outside is less
than the concentration on the inside, water will pass out of
the cell.
When a cell has a lower concentration of water on
the inside than that of pure water on the outside, the differ­
ence between the two concentrations can be measured by the
pressure that would need to be applied to the cell in order
to prevent the entrance of water.
This pressure is known as
osmotic pressure.
Any change in the cell content, by the addition from
the outside of mineral salts or the formation of a new sol­
uble substance in the cell will have an effect upon the os­
motic pressure.
A change in the concentration of the solu­
57
tion surrounding the cell will change the rate of flow of
water into the cell.
Thus, osmotic pressure does not re­
main at a fixed value but will change in accordance with the
factors which influence it.
High osmotic pressure becomes extremely important to
plants in places of little water, such as the desert regions
of the world.
The balance of pressure must always be kept
on the side favoring the intake of water.
This must increase
as the surroundings of the plants become drier.
If the plants
growing in dry habitats could not produce high osmotic pres­
sures, water would soon be taken from them, and as the soil
became drier this would naturally result in the death of such
plants.
Fitting (l91l) sees in the high osmotic pressures of
desert plants a twofold significance.
In the first place
it increases their power of suction, thus enabling the plant
to draw the necessary water from very dry soil with a consid­
erable water-retaining capacity.
Secondly, a high concen­
tration of the cell sap retards transpiration, for the high­
er the concentration of a solution, the lower the vapor pres­
sure at its surface, and the slower the rate of evaporation.
Fittingfs theoretical conclusions regarding the advan­
tages of high osmotic pressures were at first seriously dis­
puted, but later his actual data were confirmed by a series
of investigations.
All these investigations agree that in
general the drier the habitat, especially as regards the
amount of water in the soil, the higher are the osmotic pres-
58
sures of the plants occupying the habitat*
Maximov (1935) states that the significance of high
osmotic pressures during wilting is manifold.
First, a high
concentration of the cell sap of xerophytes may be the result
of the accumulation of substances which protect the protoplasm
from coagulation and desiccation.
The high osmotic pressures
of many desert plants are caused by the accumulation in the
sap of salts and of organic substances about which little is
known at present.
Secondly, a high osmotic pressure of the sap, by caus­
ing considerable tension of the cell walls, prevents visible
wilting for a long time, even though the water deficit con­
tinues to increase.
JLLso a high osmotic pressure of the sap
retards the desiccation of the plant♦
Lastly, desert soils, in consequence of weathering,
coupled with the small amount of leaching out of soluble salts,
have always a more or less highly concentrated soil solution.
The plants of the dry places have to obtain water from a more
or less concentrated soil solution, and if the resulting os­
motic resistance to absorption is to be overcome the osmotic
pressure of the plant sap must be increased sufficiently to
develop a suction pressure greater than that of the soil solu­
tion.
It is very possible that this is the most important
function of a high osmotic pressure in the cells of many
xerophytes•
The Hole fif Bound Water i& Living Organisms. - Gortner
(1929) states that the water in a biological organism may
59
exist in part as liquid water containing the truly dissolved
medium for the gels
and sols making up the organism.
A large part of the water,
however, is Abound11 by the colloidal micelles, and in this
bound condition may exhibit entirely different properties
from water in bulk.
Every organ and cell of a biological
organism has a definite fluid content and a turgidity which
is regulated by the bio-colloids present in that organ or
cell.
In some instances a considerable variation in water
content and turgidity may take place and life still be pos­
sible.
In other instances rather minor changes will cause
the death of a cell.
Robert Newton (1922) at the Minnesota Agricultural
Experiment Station, conducted a series of investigations on
the chemical and chemico-physical properties of winter wheat
plants in order to see whether or not he could differentiate
any property which would account for winter hardiness.
On
December 9, following the onset of winter temperatures, a
third collection was made.
It was found that practically no
sap could be expressed from the leaves of the hardier variaties even when the pressure employed exceeded 400 atmospheres.
These observations gave a clue as to the nature of winter
hardiness in wheat, and indicated that there was an elabora­
tion of hydrophilic colloids in the plant tissues which had
such a high imbibition capacity that all or nearly all of
the water in the wheat leaves was in a bound condition, and
in such a condition the water was either no longer able to
60
freeze, or if it did freeze, did not form sufficiently large
ice crystals to disrupt the protoplasm*
Newton found that the wheats that had been grown under
uniform temperature conditions in the greenhouse could not be
differentiated in regard to their winter hardiness by any ap­
preciable difference in their ability to hold water against
pressure, but that if they were subjected to a preliminary
nhardening off** period, the amount of water which could be
expressed from 100 grams of leaves at 400 atmospheres of
pressure could be definitely correlated with the winter hardi
ness of the variety*
In the summer of 1922, Harris and his co-workers ap­
plied the technique of Newton and Gortner to drought resist­
ance problems, utilizing as materials cereals which were
growing under dry-land farming conditions and under irriga­
tion in Utah*
They found in general, that when cereals have
an abundant supply of moisture, there is relatively little
tendency for the development of hydrophilic colloids and the
elaboration of bound water;
whereas when they are growing
in conditions of stress, the onset of drought causes a great­
er proportion of the water in the tissues to be transformed
from a free to a bound condition*
Newton, in Alberta, continued the studies of bound and
free water as related to drought resistance and has demon­
strated quantitatively that drought resistance of agricultur­
al crops and native grasses is related to, or at least that
drought resistant varieties can be differentiated by, bound
61
water content.
The following table shows a biochemical ex­
planation of the reason as to why timothy almost invariably
fails under the climatic conditions of western Alberta and
why western rye grass will successfully grow under the Al­
berta moisture conditions.
(Timothy apparently does not
possess the ability to bind water, whereas rye grass does
possess such ability.)
Bound Water and Osmotic Pressure of Timothy and Western Rye
Grass Collected from the University of Alberta Experimental
Plots in 1924. (Data of Newton and Co-workers)
Species
Phleum pratense
Agropyron tenerum
Date of
Collection
July
July
August
July
August
16
29
22
29
22
Osmotic
Pressure
Atm.
11.6
8.9
8.8
12.5
15.9
Bound
Water
Per cent
1.4
0.5
0.5
6.3
10.1
It appears that the cell activities of both plant and
animal organisms are to a large measure regulated by a bound
free water equilibrium which can, under certain condi­
tions of stress, be shifted in one direction or another in
order to provide for the preservation of the species.
CHAPTER VII
SUMMARY
Diversities in Placement of Plants- - Rorippa nasturtium-aauaticum. a plant that grows in slow-moving streams,
had the lowest osmotic pressure, (9*403 atmospheres), the
greatest percentage of total water, but was sixth in percent­
age of bound water and fourth in rate of water loss.
Twenty-
five and five-tenths per cent of its water was held as bound
water.
This was ten
per cent more than the lowest percent­
age, found in Salsola kali. which held 15.22 per cent of its
moisture as bound water.
The juvenile leaves of Eucalyptus were second from
the lowest in osmotic pressure, (11.286 atmospheres), but
were twelfth in bound water, which was 36.76 per cent.
The
agreement was close between per cent of water and rate of
water loss, the standing being 8 and 7 respectively.
Bursera microphvlla was third in osmotic pressure,
second in bound water, seventh in per cent of water, and
eleventh in rate of water loss.
The rate of water loss was
very slow for such a small per cent of bound water.
The most rapid rate of water
loss was found in Salix
gooddingii; yet it was only eleventh in total moisture con­
tent.
This is a reversal of the factors as found in Bursera
mlnrophvlla.
In the case of Salix gooddingii more water
was bound and a more rapid loss occurred than in Bursera
microphvlla. which had a much smaller amount of bound water.
The adult leaves of Eucalyptus had a rapid rate of
63
water loss, being third when compared with the other plants.
For water percentage these adult leaves were fourteenth, and
in percentage of bound water, thirteenth.
Here we find a
contradiction to the actions of the juvenile leaves.
adult leaves the bound water is greater in amount;
In the
yet the
rate of loss is faster than in the juvenile leaves.
Salsola kali was tenth in osmotic pressure (19.886
atmospheres); yet at the same time it contained the lowest
per cent of bound water, which was 15.22 per cent.
It was
second in containing a high percentage of moisture, but lost
its moisture at a slower rate than many other plants having
a higher percentage of bound water.
This plant is a parallel
to Bursera microphvlla in that it has a low percentage of
bound water but yet has a low rate of loss.
The cultivated Japanese privet, Ligustrum japonicum.
was twelfth in osmotic pressure (22.06 atmospheres), but was
low in bound water, high in moisture content, and had a rapid
loss of water.
An interesting inconsistency is found in Larrea divaricata, which was fourteenth in osmotic pressure, fifteenth in
bound water, sixteenth in moisture percentage, but lost its
water so rapidly that it was placed sixth.
Atriplex polvcarpa is the most drought resistant among
the species investigated according to the data presented in
Tablds X and XI.
64
TABLE X
PLANTS ARRANGED TO SHOW THEIR RELATIVE POSITIONS
AS DETERMINED BY THE OSMOTIC PRESSURE,
PER CENT OF BOUND WATER, PER CENT OF FREE WATER
AND INCIPIENT TRANSPIRATION
Species
Rorippa nasturtium
Eucalyptus globulus
juvenile leaves
Bursera microphylla
Salix gooddingii
Medicago sativa
Eucalyptus globulus
adult leaves
Amar&nthus palmeri
Ricinus communis
Populus fremontii
Salsola kali
Prosopis chilensis
Ligustrum japonicum
Olneya tesota
Larrea divaricata
Atriplex elegans
Atriplex polycarpa
Osmotic
Pressure
Lowest
First
Bound
Water
Lowest
First
Free
Water
Highest
First
Average
Water Loss
Highest
First
1
Z
6
12
1
8
4
7
3
4
5
6
2
7
5
13
7
11
4
14
11
1
10
3
7
8
9
10
11
12
13
14
15
16
9
11
4
1
10
3
8
15
14
16
6
5
10
2
12
3
13
16
9
15
8
5
9
14
13
2
16
6
12
15
65
TABLE XI
SPECIES ARRANGEMENT ACCORDING TO THE OSMOTIC PRESSURE
FOLLOWED BY THE PER CENT OF BOUND WATER AND PER CENT
OF FREE WATER
Species
Rorippa nasturtium
Eucalyptus globulus
juvenile leaves
Bursera mierophylla
Salix gooddingii
Medicago sativa
Eucalyptus globulus
adult leaves
Amaranthus palmer!
Ricinus communis
Populus fremontii
Salsola kali
Prosopis chilensis
Ligustrum japonicum
Olneya tesota
Larrea divaric&ta
Atriplex elegans
Atriplex polycarpa
Osmotic
Pressure
Bound
Water
Free Water
9*403
11.286
25.40
36.76
1441.43
224.61
11.698
14.073
14.680
15.436
19.70
26.06
25.04
41.40
225•36
164.66
308.50
115.12
17.722
18.668
19.520
19.886
20.480
20.060
22.560
28.267
49.530
66.928
27.38
29.72
21.77
15.22
27.67
21.46
26.21
50.94
48.14
90.37
243.43
295.76
194.17
335.82
128.50
322.05
207.91
66.28
195.97
110.01
CHAPTER VIII
CONCLUSION
The assumption that drought resistant plants have a
high osmotic pressure, a high percentage of bound water, a
low percentage of total water In the leaf and a low rate of
loss of water from the leaf holds true in the extremes for
the plants examined.
The rather wide divergences in the results for the
plants pointed out are examples that tend to disprove the
assumptions set up from the results of other investigators.
The results of the experiments presented in this paper
indicate that the value of any one factor cannot be used as a
direct indication of the value of the other three factors.
Evidence is presented to show that the greater the
differences between the values for any one factor as deter­
mined for two species, however, the more likely it would be
that one would find a similar difference for the other factors.
The evidence indicates physiological specificity, one
species being high in one factor and low in another.
To extend this investigation valuable data could be
found by comparing the activities of the same plant over a
longer period of time.
If the changes in the same plant
could be followed through its life cycle or over a period of
one year, one could determine more exactly the nature of the
changes in each factor independently and its influence on the
other factors.
The influence of the ages of the leaves
67
should be included.
The value of using four or more factors which reveal
the physiological behavior of a plant makes it possible to
select the most drought resistant plant when such measure­
ments are applied to several species.
Furthermore, degrees
of drought resistance in relation to the most drought resist­
ant plant can be ascertained.
The average of the factors for each plant places the
plants in direct agreement with each other, according to the
relative degree of dryness in which each plant grows.
TABLE XII
PLANTS ARRANGED TO SHOW THE RELATIVE DEGREE OF
DROUGHT RESISTANCE OF EACH SPECIES AS SHOWN
BY THE AVERAGE OF ALL FACTORS AS GIVEN IN TABLE X
Species
Average of Factors
Rorippa nasturtium
3.00
Ligustrum japonicum
5.00
Bursera mierophylla
5.75
Salix gooddingii
5.75
Medicago sativa
6.00
Salsola kali
6.75
Eucalyptus globulus
juvenile leaves
7.25
Ricinus communis
7.25
Amaranthus palmeri
7.50
Populus fremontii
8.00
Eucalyptus globulus
adult leaves
9.00
Prosopis chilensis
11.50
Olneya tesota
12.50
Atriplex elegans
12.50
Larrea divaricata
12.75
Atriplex polycarpa
15.50
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