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00221589.1971.11514413

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Journal of Horticultural Science
ISSN: 0022-1589 (Print) (Online) Journal homepage: http://www.tandfonline.com/loi/thsb19
Induction of flower senescence and
gynaecium development in the carnation
(Dianthus caryophyllus) by ethylene and 2chloroethylphosphonic acid
R. Nichols
To cite this article: R. Nichols (1971) Induction of flower senescence and gynaecium development
in the carnation (Dianthus caryophyllus) by ethylene and 2-chloroethylphosphonic acid, Journal of
Horticultural Science, 46:3, 323-332, DOI: 10.1080/00221589.1971.11514413
To link to this article: http://dx.doi.org/10.1080/00221589.1971.11514413
Published online: 27 Nov 2015.
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Date: 26 October 2017, At: 05:35
J. hort. Sci. (1971) 46, 323-332
Induction of flower senescence and gynaecium development in the
c~rnation (Dianthus caryophyllus) by ethylene and
2-chloroethylphosphonic acid
By R. NICHOLS
Glasshouse Crops Research Institute, Littlehampton, Sussex
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SUMMARY
The absorption of solutions of 2-chloroethylphosphonic acid (CEPA) or 2, 4-dichlorphenoxy acetic acid (2, 4-D) at 100 mg 1-1 through cut stems, or of ethylene
gas, accelerated the senescence of cut carnation flowers. Accelerated growth of the
ovary wall, placenta and receptacle accompanied wilting of petals, a typical
symptom of senescence, both in the intact or cut flower. Fresh weight, dry weight
and girth of the ovary were significantly greater in flowers treated with CEPA or
2, 4-D than in controls held in water. The CEPA treatment was less effective in
promoting dry weight increase of the ovary if the petals were removed. CEPA and
2, 4-D released ethylene or induced its formation in the carnation flower.
On the grounds that growth changes in the ovary, induced by ethylene,
simulate natural pollination and fertilization, except for seed development, it is
postulated that ethylene acts as a terminal growth regulator in the carnation.
THE longevity of the inflorescences of a growing flower crop is determined by environmental
and biotic factors, but little is known about the internal mechanisms which govern senescence of the flower while attached to the plant or after cutting. It is reasonable to postulate
that growth substances are involved, and gibberellin-like substances have been reported
in floral parts of carnations (Jeffcoat eta!., 1969). Harris eta!. (1969) showed that anthesis
was hastened by injections with gibberellic acid. Thus gibberellins are likely to be concerned
in the early development of the flower. There is evidence that gibberellins and ethylene
act in opposition (Scott and Leopold, 1967), and it is known that carnation flowers produce
ethylene (Phan, 1963). It is therefore of interest to know whether ethylene is concerned in
the later development and senescence of the carnation floral parts. The accelerated senescence of carnation petals caused by exposure to ethylene has been known for a long time
(Crocker and Knight, 1908), and the quantitative response has also been described (Nichols,
1968b).
However, other factors are known to promote wilting and petal senescence, pollination
for example. The glasshouse-grown carnation flower is relatively long-lived in the absence
of pollination (Nichols, 1966), but wilting of the petals may occur within 2 to 4 days following pollination and fertilization. This is a common phenomenon in flowering plants (Robbins
et a!., 1958). In Cymbidium flowers naphthalene acetic acid can simulate post-pollination
changes (Arditti and Krauft, 1969). Fading of Vanda flowers is induced by indolyl acetic
324
Induction offlower senescence and gynaecium development in carnations
acid or pollination, and is caused by ethylene (Burg and Dijkman, 1967). Hall and Forsyth
(1967) have demonstrated that excised flowers of Vaccinium and Fragaria produce ethylene
after pollination or treatments with auxin. There is evidence, then, that pollination and
growth regulators can induce the formation of ethylene.
In this paper evidence will be presented that 2-chloroethylphosphonic acid (CEPA)
and 2, 4-dichlorphenoxy acetic acid (2, 4-D) simulate post-pollination phenomena in the
carnation, namely, accelerated senescence of the petals and the initiation of ovary develop·
ment. It is considered that the activity of these growth substances is. caused by ethylene.
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MATERIALS AND METHODS
Flowering shoots of Dianthus caryophyllus were cut when the flowers were at the stage
of development described as fully open in commercial terminology; at this stage the outer
petals were reflexed, so that they were approximately at right angles to the axis of the stem.
The cultivar 'White Sim' was used throughout except where otherwise mentioned. Stems
were cut to a length of approximately 300 mm and the lower leaves were removed, leaving
two to three leaf pairs below the calyx.
CEPA (2-chloroetbylphosphonic acid, Amchem 68-241, 94% acid equivalent) was
dissolved in water and the pH of the solution adjusted to pH 6. 3 with O.lN NaOH. Stems
were either placed in this solution or the petals were lightly sprayed with it to run-off, using
an atomizer. Fresh weights of ovaries were determined by removing the petals and cutting
the ovary at the point of insertion on the receptacle; dry weights were determined after
drying at 90 oc for 24 hours.
All observations on cut flowers were made after a specified number of days at 18.3 oc,
counting the day of harvest as day 0.
Ethylene determinations were made by gas chromatography using a flame-ionization
detector and separation on Porapak S.
RESULTS
Preliminary experiments were carried out to find a suitable concentration of CEPA
solution which would induce petal senescence within 2 days when the stems of cut flowers
were immersed in it. It was found with both 'Red Sim' and 'White Sim' cultivars that concentrations within the range 0. 1 to 10.0 mg 1-1 caused no visible symptoms different from
water controls. Treatments with 100 and 1000 mg I-1 induced petal senescence and caused
the ovary to increase in size within 2 days from the beginning of treatment. However, in the
1000 mg 1-1 solution, stems developed red colouration and there was some mottling of the
upper leaves, symptoms which were not observed with the weaker solutions used in subsequent experiments.
Effect of CEPA on ovary development and fresh weight of the flower
The change in mean fresh weight of five flowers treated with CEPA is shown in Figure 1.
Petals wilted on day 2 in the 100 mg 1-1 solution and on day 6 in the other treatments. The
drop in fresh weight as the petals wilted was similar to that previously reported for carnation
flowers treated with ethylene (Nichols, 1966). When the petals from the five flowers in each
treatment had wilted, the ovaries were removed and their lengths and diameters were
R.
325
NICHOLS
120
-;;
....~
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c;
!:
-~
L..
....0
g/OO...J.---r------,..--'
1' \
:;;
z
0
...
3
~
4
s
Days
D-
•
90
FIG.
I
Change in fresh weight of flowers treated with CEPA.
• = 100 mgl- 1 ; e = 10 mg 1-1 ; .A.= control; W =petals wilting.
measured. It was observed that, at comparable stages of wilting, the ovaries from the flower
treated with 100 mg 1-1 solution were larger than those from the other treatment (10 mg 1-1 )
or the controls. These observations were of particular interest, because wilting of petals and
enlargement of the ovary (capsule) are the natural response of the flower to pollination
and fertilization.
The experiment was therefore repeated, slightly modified, to minimize the effect of
exogenous ethylene released from the CEPA solution. Cut flowers were placed in BUchner
flasks containing CEPA solution (100 mg 1-1). Air was drawn through the side-arm of the
flask to remove free gaseous ethylene from the head space above the CEPA solution.
Analysis of the air around the petals confirmed that ethylene was absent ( <0. 02 vpm), and
the response of the flower parts could therefore be attributed to the absorption of CEPA
by the cut stem. Petals wilted within 2 days after placing the stems in the CEPA solution,
at which stage the stems were rinsed and the flowers transferred to deionized water for
observation.
Ten flowers were dissected at 2, 4, 7 and 9 days from day 0. The fresh and dry weights,
diameters and lengths of the ovaries were measured. A comparison of the dry weights and
diameters of ovaries from treated and untreated flowers is illustrated in Figures 2a and b.
326
Induction of flower senescence and gynaecium development in carnations
•
65
;
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~
,/
,,"",'' ' ',,
w
"
"'1>
I
,,
.
t
-
-A
~-------b.'"'
I
t
I
10-0
e
e
... 9·0
!:
..
e
...,
.!:!
w
.,
''1>
2
3
f
''--------A------1>
4
5
6
Days
FIG.
2
Increase in dry weight (a) and diameter (b) of ovary in CEPA solution, 100 mg 1-1 •
• = 100 mg 1-1 ; !:::,. =control; W =petals wilting.
Ovaries increased in diameter and in fresh and dry weights for about 7 days in CEPAtreated flowers, although the relative growth rate was highest during the first 2 days.
In untreated flowers, ovaries grew very slightly for 2 days and then growth ceased. Since
the swelling of the ovaries of the CEPA-treated flowers was accompanied by an increase in
dry weight, it is suggested that ethylene, released from the CEPA, initiates the diversion
of nutrient to the gynaecium; the increase in weight could not be accounted for by absorption
and accumulation of CEPA in the transpiration stream. It is, however, significant that the
increase in weight of the ovary did not occur following wilting of the petals at the end of
"normal" senescence; this point will be returned to later. The response to CEPA occurred
both in daylight and in continuous darkness.
R.
327
NICHOLS
The experiment was repeated with cut flowers of 'Red Sim' sampled at 3, 6 and 9
days. The effects of the CEPA (Table I) were similar to those described for 'White Sim'.
To determine whether the response to CEPA was caused by ethylene, air was drawn
over a CEPA solution (pH 3. 1) in a closed 5-1 vessel and passed through a 20-1 jar containing
cut carnation flowers in water. Ethylene(> 1. 0 vpm) was detected in the air-stream passing
from the CEPA solution to the cut flowers. Flower petals wilted within 2 days, and ovaries
were measured 2 days later {Table II). A similar result was obtained by passing ethylene
from a commercial cylinder (0. 2 vpm) over cut carnation flowers. Clearly, the effect of
ethylene gas was similar to that produced by CEPA absorbed as a solution.
TABLE
I
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Growth of ovaries in 'Red Sim' carnations treated with CEPA solution by stem absorption
Days from start
of treatment
Mean fresh wt
Mean dry wt
g
g
Wt
(untreated) 0
3
6
9
w
Et
0.141
0.186
0.276
0.179
0.337
0.185
0.355
S.E. 0.0131
E
0.0292
0.0347
0.0537
0.0334
0.0655
0.0387
0.0682
S.E. 0.0024
Diameter
nun
w
E
6.09
6.90
9.3
7.04
10.0
7.40
9.9
S.E.O.I7
t W =stems in water; E =stems in CEPA.
TABLE II
Increase in mean weights of ovaries treated with
ethylene liberated from CEPA solution
Fresh wtt
g
Control
Ethylene
Difference
0.171
0.314
0.142***
Dry wtt
g
0.0306
0.0557
0.0251***
t Measured on day 4.
• **
Significant at 0. I % level.
Effect of removing petals on ovary development
The source of the dry matter which contributed to the increase in dry weight of the
ovary reported in the previous experiments is not known for certain. Since the increase in
growth of the ovary is initiated or accompanied by wilting of the petals, it is reasonable to
postulate that some translocation occurs between these organs; the alternative or additional
source would be the leaves and stem. In order to test the effects of the petals, flowers with
and without petals were treated with CEPA (100 mg 1-1) by stem absorption and the dry
weights of the ovaries compared with those of untreated flowers (Table III).
Induction of.flowe; senescence and gynaecium development in carnations
328
TABLE
III
Effect of CEPA treatment in the presence and absence of petals on ovary development
Treatment
Petals
+
+
CEPA
CEPA
Water
Mean fresh wtt
Mean dry wtt
g
g
0.330
0.217
0.196
0.0639
0.0463
0.0355
Mean diametert
mm
9.7
7.7
6.9
t Measured on day 5.
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A comparison by the Studentized 't' range of mean dry weights of ovaries after treatment gave the following relationships:
ro
~>
~D
CEPA
> CEPA
>
water
plus
minus
plus
flower petals
flower petals
flower petals
These results suggest that some translocation occurs between the vegetative organs and
the ovary, but since the growth of the ovary was greatest when petals were present and
induced to wilt by CEPA, it seems likely that some dry matter is also transferred from the
petals. Support for this view came from the observations that fresh and dry weights of
petals declined when the petals wilted. The difference between control (untreated) and
CEPA-treated (wilted) petals was 0. I to 0. 2 g dry weight (n = 6). The loss in weight of
treated petals cannot be accounted for entirely by translocation to the ovaries, because an
increase in respiration occurs, of about 25 to 40% (Nichols, 1968b), when wilting is induced
by ethylene. It follows that a part of the dry matter lost can be accounted for by an increased
output of carbon dioxide.
Initiation of ovary growth by 2, 4-D
Since exogenous ethylene and ethylene derived from CEPA by stem absorption initiate
ovary growth, other growth regulators which promote the synthesis or liberation of ethylene
might be expected to have a similar effect. Carnation flowers were therefore treated with
a range of 2, 4-D solutions by stem absorption, Morgan and Hall (1962) having shown that
2, 4-D promotes ethylene production in cotton. It was found that a treatment with a 100 mg
1-1 solution of 2, 4-D caused wilting of petals within 2 to 3 days from the beginning of
treatment, and, in common with the CEPA or ethylene treatments, this was accompanied
by an increase in fresh weight, dry weight and growth of the ovary. Mean dry weights of
ovaries from control flowers and from flowers treated with 2, 4-D were 0.046 g and 0.070 g
respectively (significantly different at 0.1 %) in the early stages of petal wilting. Rates of
ethylene production from two of the wilting flowers treated with 2, 4-D were 0.3 and 0.5
p.l h-1, which are comparable to the rates for flowers wilting at the end of "normal" senescence with their stems in water.
It can be seen that 2, 4-D induces ovary development, but it is likely to exert its effect
through the liberation of ethylene, for reasons which will be given later. Other synthetic
growth regulators would probably act in a similar way.
R.
329
NICHOLS
Treatment of intact flowers on the growing plant
Fully open flowers growing in a glasshouse were sprayed to run-off with CEPA solution
(100 mg I-1). Petals wilted within 2 to 4 days, in contrast to those of untreated control
flowers, .which wilted about the 7th or 8th day. Ovaries were removed on the 7th and 13th
days and their dry weights determined (Table IV). The increase in dry weight of the ovary
as a result of treatment was similar to that described earlier for the cut flower.
TABLE IV
Increase in mean diameter and dry weights ofovaries from intact flowers on the growing plant by spray treatment
with 100 mg !-1 CEPA
Dayst
7
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0
Treated
Untreated
Diam.
mm
Drywt
7.1
0.0417
g
Diam.
mm
8.5
7.2
13
Drywt
g
0.0569
0.0445
Diam.
mm
9.3
7.1
Drywt
g
0.0701
0.0461
t From spray treatment.
In both the growing and the cut flower the increase in diameter of the ovary was a
result of increased growth of the ovary wall. The placenta and receptacle also enlarged,
but since the seeds were not fertilized and remained relatively small, effectively the volume
of the loculus increased. There were no other visible effects on leaf or stem with the concentrations of CEPA used.
Effect of pollination
It is generally considered that pollination and fertilization rarely occur in the carnation
under protected cultivation. The reasons for this view are that anthers are rare in 'Sim'
cultivars and there are few pollinating insects in the glasshouse. However, it was found that
a proportion of hand-pollinated flowers of 'White Sim' wilted within a few days and produced a surge of ethylene.
Flowers from a population of Dianthus sp. which produced anthers freely were used
as pollen parents. Dehisced anthers were brushed over the stigmas of fully open 'White
Sim' flowers in the glasshouse. Sixteen flowers were pollinated, using two different pollen
donors. Eight wilted within 3 days, but none of the unpollinated controls had wilted
by the 4th day. The petals of the pollinated flowers became in-rolled and limp and flaccid,
and were similar in appearance to flowers which had been treated with ethylene or CEPA.
Two pollinated flowers, showing symptoms of early wilting, were transferred to respiration
jars and their ethylene production measured (Nichols, 1966); the mean values for each flower
were 0. 28 p.l h-1 and 0. 50 p.l h-1. The similarity of these results to those with the 2, 4-Dtreated flowers mentioned above and with "normal" wilting flowers is noteworthy and
suggests that there is a common mechanism which initiates the wilting of petals, whether
as the result of pollination (or fertilization), chemically induced wilting (e.g. with 2, 4-D)
or normal sensescence. In further pollination studies seeds were found in pollinated flowers,
330
Induction offlower senescence and gynaecium development in carnations
the petals of which had not wilted significantly earlier than those of unpollinated controls.
Clearly, other factors, for example the amount and viability of pollen, must be considered
when attempting to explain the initiation of the wilting syndrome after pollination.
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DISCUSSION
There seems little doubt that ethylene can be regarded as a growth regulator (Pratt
and Goeschl, 1969). The following observations support the hypothesis that ethylene
functions as a naturally occurring growth regulator in the carnation flower:
(i) Pollination and fertilization may initiate wilting of the petals, growth of the ovary
(capsule) and seed development.
(ii) Absorption of a known ethylene-producing compound (e.g. CEPA) by cut flowers,
or spray treatments of growing flowers, causes wilting of petals and growth of the ovary.
(iii) Exogenous ethylene at suitable concentrations has the same effect on cut flowers
as CEPA treatment or pollination in so far as ovary growth and petal senescence are
concerned.
(iv) Wilting of the floral organs, on or off the plant, is accompanied by liberation of
ethylene.
It is possible, therefore, that some post-harvest phenomena can be explained by changes
in endogenous levels of ethylene in the flower. For example, high concentrations of carbon
dioxide or low levels of oxygen delay senescence of carnation flowers (Smith et al., 1966;
Nichols, 1968a), but there is little residual effect of these gas treatments once the flowers are
transferred to air (Hanan, 1967). Burg and Burg (1965) have described carbon dioxide as a
competitive inhibitor of ethylene action, and the production of ethylene in plant tissues
requires oxygen. In cut carnation flowers, ethylene formation is suppressed by about 4%
carbon dioxide, or reduced in atmospheres containing less than 4% oxygen (Nichols,
1968b). However, it is probable that once flowers are moved from the modified gas atmospheres and returned to air, ethylene levels rise and symptoms of senescence develop.
Ethylene oxide, an antagonist of ethylene, has been shown to delay the wilting of petals
of cut carnations (Lieberman et a!., 1964). Low temperatures are well known to delay
flower sencescence and reduce the rate of ethylene production. Clearly, other interpretations
canexplain these results, for example, the temperature and controlled atmosphere treatments
affect the respiration of plant tissue and may affect the metabolism and growth of microorganisms, but there may be an interaction between these phenomena and the endogenous
ethylene system.
Evidence has been presented that ethylene promotes an increase in dry weight of the
ovary, probably as a result of the redistribution of materials within the floral and vegetative
organs. This is analogous to what happens following pollination in the intact flower. Although it was surprising to find this also occurred with the cut flower, Ulrich and Paulin
(1957) have reported the translocation of water and materials between the flowers of cut
inflorescences of Iris germanica. The observation that 2, 4-D initiates similar changes
in the ovary can be explained as indirect stimulation by endogenous ethylene, auxins being
known to cause ethylene formation in plant tissues (Morgan and Hall, 1962; Abeles, 1966).
In the course of the experiments it was noted that development of the ovary did not
occur after petals wilted at the end of "normal" senescence in air. In this instance, however,
R. NICHOLS
331
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the flowering stems were under low light intensities and presumably little fresh assimilate
was formed during the period of observation. It is also possible that little respirable substrate remains to be translocated, although the leaves may not senesce for some weeks
after the flower has wilted.
Thus, it appears that gibberellin-like compounds are involved in the early development
of the carnation flower (Harris eta/., 1969) and ethylene towards the end. The switch from
floral to ovary development is normally initiated by pollen, which provides the stimulus
for seed growth. If ethylene mediates the resulting growth and development following
pollination, as proposed here, an argument which supports the findings of Burg and
Dijkman (1967) for Vanda sp., then some part of the gynaecium must be the active centre.
In view of the work of Hall and Forsyth (1967) this is likely to be the style, and this point
is being investigated.
REFERENCES
ABELES, F. B. (1966). Auxin stimulation of ethylene evolution. Pl. Physio/., Lancaster,
41, 585-8.
ARDITTI, J., and KRAUFT, R. L. (1969). The effects of auxin, actinomycin D, ethionine,
and puromycin on post-pollination behavior by Cymbidium (Orchidaceae) flowers.
Am. J. Bot., 56, 620--8.
BuRG, S. P., and BURG, E. A. (1965). Ethylene action and the ripening of fruits. Science,
N.Y., 148, 1190--6.
BuRG, S. P., and DuKMAN, M. J. (1967). Ethylene and auxin participation in pollen induced
fading of Vanda orchid blossoms. Pl. Physiol., Lancaster, 42, 1648-50.
CROCKER, W., and KNIGHT, L. I. (1908). Effect of illuminating gas and ethylene upon
flowering carnations. Bot. Gaz., 46, 259-75.
HALL, I. V., and FORSYTH, F. R. (1967). Production of ethylene by flowers following pollination and treatments with water and auxin. Can. J. Bot., 45, 1163-6.
HANAN, J. J. (1967). Experiments with controlled atmosphere storage of carnations. Proc.
Am. Soc. hort. Sci., 90, 370--6.
HARRIS, G. P., JEFFCOAT, B., and GARROD, J. F. (1969). Control of flower growth and
development by gibberellic acid. Nature, Lond., 223, 1071.
JEFFCOAT, B., Scorr, M.A., and HARRIS, C. P. (1969). Studies on the glasshouse carnation:
the detection of gibberellin-like substances in the flower and an effect of gibberellic
acid on petal growth. Ann. Bot., 33, 515-21.
LIEBERMAN, M., AsEN, S., and MAPSON, L. W. (1964). Ethylene oxide, an antagonist of
ethylene in metabolism. Nature, Lond., 204, 756--8.
MoRGAN, P. W., and HALL, W. C. (1962). Effect of 2, 4-dichlorphenoxy acetic acid on the
production of ethylene by cotton and grain sorghum. Physiologia Pl., 15,420--7.
NICHOLS, R. (1966). Ethylene production during senescence of flowers. J. hort. Sci., 41,
279-90.
NICHOLS, R. (1968a). The storage of cut flowers in gas flows. Rep. Ditton Lab. for 1967-68,
40--1.
NICHOLS, R. (1968b). The response of carnations (Dianthus caryophyllus) to ethylene.
J. hort. Sci., 43, 335-49.
6
332
Induction offlower senescence and gynaecium development in carnations
Downloaded by [UNSW Library] at 05:35 26 October 2017
PHAN, C. T. (1963). The production of ethylene by flowers. C.r. hebd. Seanc. Acad.
Agric. Fr., 49, 53-9.
PRATT, H. K., and GOESCHL, J.D. (1969). Physiological roles of ethylene in plants. A. Rev.
Pl. Physiol., 20, 541-84.
ROBBINS, W. W., WEIER, T. E., and STOCKING, C. R. (1958). Botany.]. Wiley Inc. New York.
ScoTT, P. C., and LEOPOLD, A. C. (1967). Opposing effects of gibberellin and ethylene.
Pl. Physiol., Lancaster, 42, 1021-2.
SMITH, W. H., PARKER, J. C., and FREEMAN, W. W. (1966). Exposure of cut flowers to
ethylene in the presence and absence of carbon dioxide. Nature, Lond., 211, 99-100.
ULRICH, R., and PAULIN, A. (1957). Observations sur les inflorescences isolees d'Iris.
Revue gen. Bot., 64, 93-105.
(Received 12/11 flO.)
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