Lecture 3: Plant anatomy and physiology by Edgar Moctezuma, Ph.D. TodayвЂ¦ вЂў Announcements вЂў Plant Anatomy вЂ“ Cells вЂ“ Tissues вЂ“ Organs вЂў Plant Physiology вЂ“ Water & sugar transport вЂ“ Plant hormones AnnouncementsвЂ¦ вЂў Labs start this week вЂ“ get your lab manual. вЂў BSCI 125 students: if you have the following sections: вЂ“ вЂ“ вЂ“ вЂ“ 1109, 1110 Tues. 3:30-5:30 or, 1113, 1114 Wed. 12-2 or, 1115, 1116 Wed. 3-5 or 1123, 1124 Thurs. 3:30-5:30, and you can switch to an open section (Monday or Wed. 9:00-11:00), please try to do so. Thanks! вЂў Taking care of your plant: вЂ“ Do not overwater it! Water only when soil is dry to the touch. вЂ“ Place near a sunny window. From smallest to largest plants What is plant anatomy? вЂў ANATOMY: study of the structure of organismsвЂ¦ looking at cells, tissues вЂў (Morphology: Study of form) What is plant physiology? вЂў PHYSIOLOGY: study of the function of cells, tissues, organs of living things; and the physics/chemistry of these functionsвЂ¦ Always keep in mind that in plant anatomy, morphology & physiologyвЂ¦ вЂњStructure correlates to functionвЂќ вЂў How can water move from the ground all the way to the top of a 100 m tall redwood tree? Plant Anatomy: Cells вЂў Plant cells are basic building blocks вЂў Can specialize in form and function вЂў By working together, forming tissues, they can support each other and survive вЂў Levels of organization atoms > molecules > cells > tissues > organs > whole plant > pop. Plant Tissues Types All plant organs (roots, stems, leaves) are composed of the same tissue types. There are three types of tissue: вЂў 1. Dermal вЂ“ outermost layer вЂў 2. Vascular вЂ“ conducting tissue, transport вЂў 3. Ground вЂ“ bulk of inner layers 1. Dermal tissue вЂў Epidermis is the outermost layer of cells вЂў Like the вЂњskinвЂќ of animals вЂў In stems and leaves, epidermis has cuticle, a waxy layer that prevents water loss. вЂў Some have trichomes, hairs. вЂў Root epidermis has root hairs, for water and nutrient absorption 2. Vascular tissue вЂў Transports water and organic materials (sugars) throughout the plant вЂў Xylem вЂ“ transports water and dissolved ions from the root to the stem and leaves. вЂў Phloem вЂ“ carries dissolved sugars from leaves to rest of the plant Xylem вЂў Transports water and dissolved minerals вЂў Tracheids: long, thin tube like structures without perforations at the ends вЂў Vessel elements: short, wide tubes perforated at the ends (together form a pipe, called vessel). вЂў Both cells have pits (thin sections) on the walls Tracheids Vessel elements Xylem cells вЂў Xylem cells are dead! вЂў They are hollow cells and consist only of cell wall Phloem вЂў Cells that transport organic materials (sugars) вЂў Phloem cells are ALIVE! (unlike xylem) вЂў However, they lack nucleus and organelles Phloem: transports sugars вЂў Phloem composed of cells called sieve tube members (STM) вЂў Companion cells join sieve tube members, are related, and help to load materials into STM вЂў End walls of STM have large pores called sieve plates Companion cells Sieve tube member Sieve plates 3. Ground tissue вЂў Makes up the bulk of plant organs. вЂў Functions: Metabolism, storage and support. Root Stem Leaf Plant Organs Organs: tissues that act together to serve a specific function вЂў Roots Dermal Vascular Ground вЂў Stems Dermal Vascular Ground вЂў Leaves Dermal Vascular Ground Functions of plant organs: вЂў ROOTS: Anchorage, water/nutrient absorption from soil, storage, water/nutrient transport вЂў STEMS: Support, water/nutrient transport вЂў LEAVES: Photosynthesis (food production) ROOTS вЂў вЂў вЂў вЂў вЂў вЂў ROOTS вЂњthe hidden halfвЂќ Functions of roots: Ancorage Absorption of water & dissolved minerals Storage (surplus sugars, starch) Conduction water/nutrients Anatomy of a root epidermis cortex vascular Root Epidermis вЂў Outermost, single layer of cells that: вЂ“ Protects (from diseases) вЂ“ Absorbs water and nutrients вЂў ROOT HAIRS: tubular extensions of epidermal cells. вЂў Increase surface area of root, for better water/nutrient absorption Root Hairs: water and mineral absorption Root hairs increase surface area for better absorption Root Cortex вЂў Stores starch, sugars and other substances Root Ground tissue вЂў In roots, ground tissue (a.k.a. cortex) provides support, and often stores sugars and starch (for example: yams, sweet potato, etc.) YouвЂ™re not a yam, youвЂ™re a sweetpotato! cortex Hey! I yam what I yam, man! Root Cortex: Endodermis вЂў Endodermis: the innermost layer of the cortex Root cortex: Casparian strip вЂў The Casparian strip is a water-impermeable strip of waxy material found in the endodermis (innermost layer of the cortex). вЂў The Casparian strip helps to control the uptake of minerals into the xylem: they have to go through the cytoplasm of the cell! STEMS вЂў Above-ground organs (usually) вЂў Support leaves and fruits вЂў Conduct water and sugars throughout plant (xylem and phloem) Stem anatomy вЂў Dermal, ground and vascular tissuesвЂ¦ epidermis cortex pith Vascular bundles Types of Stems Monocot stem Dicot stem Root Types of stems вЂў Herbaceous vs. Woody stems Tissues of stems вЂў вЂў вЂў вЂў Epidermis (Dermal tissue type) Provides protection Has cuticle (wax) prevents water loss Trichomes (hairs) for protection, to release scents, oils, etc. Stem Vascular tissue вЂў Vascular bundles вЂ“ composed of both xylem and phloem вЂў Xylem вЂ“ Conducts water вЂ“ Support вЂў Phloem вЂ“ Conducts food вЂ“ Support Vascular cambium Vascular cambium вЂў Occurs in woody stems вЂў Vascular cambium located in the middle of the vascular bundle, between xylem and phloem Vascular tissue: Trees вЂў Vascular tissue is located on the outer layers of the tree. bark phloem Vascular cambium xylem wood Girdling: cutting around a tree вЂў Damages the phloem and xylem, eventually killing the tree! Vascular tissue forms rings in trees вЂў Annual rings: xylem formed by the vascular cambium during one growing season вЂў One ring = one year History of the tree: annual rings Dendrochronology : tree time-keeping 1776: Declaration of US independence 1917 & 1945: Tree Survives two World Wars 1969: Man lands on Moon 1492: Columbus lands in the Americas 1620: Pilgrims land in Plymouth, Mass. 1489: Tree is planted by Native American 1861: Start of Civil War 1971: Birth Year of the IDIOT who cut down this tree!!! Ground tissue: Cortex & pith вЂў Stores food (e.g. potato) вЂў Site of Photosynthesis (when green) вЂў Support cells cortex pith LEAVES: вЂў вЂ�Photosynthetic factoriesвЂ™ of the plantвЂ¦ вЂў Function: Photosynthesis вЂ“ food production for the whole plant вЂў Blade: Flat expanded area вЂў Petiole: stalk that connects leaf blade to stem, and transports materials BLADE Leaf Anatomy вЂў Leaf anatomy is correlated to photosynthesis: Carbon dioxide + Water пѓ sugars + oxygen dermal ground vascular dermal Leaf epidermis вЂў Is transparent вЂ“ so that sun light can go through. вЂў Waxy cuticle protects against drying out вЂў Lower epidermis: stomata with guard cells вЂ“ for gas exchange (CO2, H2O in; O2 out) Leaf epidermis вЂў Trichomes (give fuzzy texture) (вЂњPanda plantвЂќ) Leaf vascular tissue вЂў VEINS пѓ vascular tissue of leaves. вЂў Veins are composed of xylem (water transport) phloem (food transport) and bundle sheaths, cells surrounding the xylem/phloem for strength & support Leaf Mesophyll вЂў Middle of the leaf (meso-phyll) вЂў Composed of photosynthetic ground cells: вЂў Palisade parenchyma (long columns below epidermis; have lots chloroplasts for photosynthesis) Spongy parenchyma (spherical cells) with air spaces around, (for gas exchange) Plant water transport вЂў How can water move from the ground all the way to the top of a 100 m tall redwood tree? Water transport in plants: вЂў The same way we drink soda from a straw! вЂў WaterвЂ™s great cohesive forces (molecules sticking to each other) and adhesive forces (attaching to walls of xylem cells) Transpiration-cohesion Theory for water transport in the xylem вЂў Evaporation of water in the leaves (through stomates) generates the вЂ�sucking forceвЂ™ that pulls adjacent water molecules up the leaf surface Water transport (cont.) вЂў Like a long chain, water molecules pull each other up the column. вЂў The column goes from roots пѓ leaves. вЂў WhatвЂ™s amazing is that the water moves up by using the sunвЂ™s evaporative energyвЂ¦ вЂў Plants control transpiration by opening/closing stomata Sugar translocation вЂў 1. Sugars made in leaf mesophyll cells (source) diffuse to phloem cells in the vascular bundles. вЂў 2. Companion cells load dissolved sugars into the phloem STM using energy (ATP). вЂў 3. Water moves into cells with high sugar concentration. вЂў 4. Osmotic water flow generates a high hydraulic pressure that moves dissolved sugars through the phloem to the rest of the plant (sink). Pressure flow in phloem вЂў Sugars made in the leaves are loaded into companion cells and into phloem STM. вЂў Water (from xylem) moves in by osmosis, creating pressure flow down the phloem. Plant Hormones вЂў вЂў вЂў 1. 2. 3. 4. 5. Chemical compounds produced by plants Effective at very low concentrations Five major hormone groups are: Auxins Gibberellins Cytokinins Abscisic Acid Ethylene 1. AUXINS вЂў Promote cell growth вЂў Involved in gravitropism and phototropism вЂў Control fruit development 2. Gibberellins вЂў Promote stem elongation 3. Cytokinins вЂў Promote cell division and organ differentiation 4. Abscisic Acid вЂў Promotes seed dormancy вЂў Causes stomata closing 5. ETHYLENE вЂў Gaseous hormone, very simple formula (C2H4) вЂў Ethylene promotes fruit ripening! Air Ethylene вЂњOne rotten apple spoils the barrelвЂќ вЂў Why? Probably due to ethylene! Rotten apple producing lots of ethylene! вЂў Autocatalytic вЂў As a response to injury Avocado ripeningвЂ¦ вЂў Place in a paper bag, with a ripe banana!