*Lab Make-up option* Dynamic Plant Plant Movements, Hormones & Defense Systems

Transcription

1 Dynamic Plant Plant Movements, Hormones & Defense Systems Resurrection plant Selaginella lepidophylla A Club moss, Lycophyta *Lab Make-up option* Weed Profile Project Pick a common weed in Oregon and create a 1-5 min presentation describing it. Find out information about: 1. Its Range 2. Origin 3. Control methods 4. Natural herbivores/pathogens? 5. Positive & negative affects of the weed in Oregon Adaptive Plants: Respond to their changing environment. 1

2 Outline Introduction: Growth Plant Hormones Plant Responses o Tropisms o Nastic responses o Phytochromes o Photoperiod/Circadian Rhythms o Dormancy o Plant defense systems Introduction Growth - Irreversible increase in mass due to division and enlargement of cells Determinate growth - Plant grows, stops growing and dies in one season. Indeterminate growth - Plant or parts of plant grow and continue to be active for several to many years. Differentiation - Cells develop different forms adapted to specific functions. Development - Coordination of growth and differentiation of a single cell into tissues and organs Plant Hormones What is a hormone? > A chemical signal. These chemicals are produced by cells in one location that influence other cells e.g. growth in another region of the organism. Typically they are proteins or steroids, which are lipid based. 2

3 First why is it important to know about plant hormones? Knowledge of plant hormones have allowed us to improve and manipulate many of our horticultural crops. Do you like having produce/flowers on demand? Potatoes year round Tomatoes in your salad anytime Roses in the winter time Tour of the Plant Hormones Giberellins Working on your seedlings right now! Named after a fungus that produces it (Gibberella fujikuroi) Affects: Germination Sprouting of buds Elongation of stems & leaves Stimulates flowering Affects the development of fruit Effect of gibberellins on cabbage Auxins Made in: Apical meristem of shoot system. Move from tip downward. Affects: Cell elongation Phototropism Development of vascular tissue Fruit development Retards senescence in leaves & fruits Several Forms: Indoleacetic acid (IAA) Phenylacetic acid (PAA) 4-chloroindoleacetic acid (4-chloroIAA) Indolebutyric acid (IBA) 3

4 Cytokinins Produced in root moves to shoot Affects: Stimulates embryo development Promotion of sprouting of lateral buds. Development of chloroplasts Stimulation of the onset of fruits Stimulate plant metabolism Delays the aging of plant parts especially leaves Abscisic Acid Produced in petiole (stalk of the leaf) Affects: Dropping of leaves Growth inhibition blocks protein synthesis Common in fleshy fruits - Prevents seeds from germinating while still on plant Induces dormancy in buds Closing of stomata Ethylene Produced by ripening fruits Affects: Ripening of other fruits Abscission of fruits & leaves Maturation of flowers Ethylene from apple caused abscission of holly leaves This is why bananas can be picked green and sent to market from Central America to the U.S. to ripen. Tomatoes, grapes and strawberries don t respond to artificial ethylene exposure. 4

5 Hijacked: Insect induced galls! How do Plants Respond to External Stimuli? o o o o o o Tropisms Nastic responses Phytochromes Photoperiod/Circadian Rhythms Dormancy Plant defense systems Phototropism 5

6 Phototropism Auxin migrates away from light, and accumulates in greater amounts on opposite side, promoting greater elongation of cells on dark side. Positive phototropism Gravitropism Gravity may be perceived by amyloplasts in root cap, by proteins on outside of plasma membrane, by whole protoplast, or by mitochondria and dictyosomes. Primary roots - Positively gravitropic Shoots - Negatively gravitropic Thigmotropism 6

7 Nastic Response: Plant response to external stimuli Mechanisms: 1. Cell enlargement/turgor movements 2. Cell division (mitosis) Examples: 1. Venus fly trap 2. Mimosa Plant Movements: Turgor movements Sleep movements - Circadian rhythms Regular daily cycles Leaves or petals fold in regular daily cycles. Members of the legume family, prayer plants Turgor movements, and stimuli of light and temperature involved. Controlled by a biological clock on approximately 24 hours cycles Appear to be controlled internally Circadian rhythm in prayer plant How do plants detect light? Phytochrome a plant pigment that literally means plant color. Found in most plant organs, especially meristems. An internal regulator. This regulator helps seeds know it is appropriate to germinate or not and if it is time to flower. 7

8 Importance of Phytochrome Photoperiodic responses Photomorphogenesis e.g. leaf expansion Greening of the leaves Germination of light sensitive plants e.g. lettuce. Types of Phytochrome Pr (inactive phytochrome) absorbs red light. Absorption peak at 660 nm in EMS. Pfr (active phtochrome) absorbs far red light which is fully reactive. AP peak at 730 nm.* Natural White light favors formation of Pfr. > Makes the plant respond by becoming green and lush. When is Phytochrome Active? Answer all the time (it is the biological clock) I. Pr converts to Pfr in daylight and the plant grows lush. II. Pfr converts to Pr when the plant is in the shade and it grows spindly to try to find light. 8

9 Sensing Time Photoperiod The initiation of flowering and other vegetative activities in reponse to relative lengths of day & night. Dormancy Period of inactivity in some plant part, usually in response to environmental cues e.g. declining day length. Quiescence The state in which a seed cannot germinate unless environmental conditions normally required for growth are present. E.g. germination in desert seeds after rains occur. Senescence The breakdown of cell components and membranes that lead to death of cell e.g. dropping leaves in the fall. Plant Defenses: Thorns Thorns: Modified stems Examples: Acacia Crataegus (Hawthorn) Giraffe Eating spiny acacia tree nevermind the thorns! giraffe_wnr- 4028c.jpg Plant Defenses: Spines Spines: Modified leaves Examples: Opuntia spp. Prickly pear cactus 9

10 Plant Defenses: Prickles Prickles: epidermal cells Examples: Rosa spp. Plant Defenses: Trichomes Trichomes: hairs Can be glandular Example: tomato Plant Defenses: Trichomes Glandular trichome of Stinging Nettle Urtica dioica 10

11 Plant Defenses: Sap/Latex Milkweed: Asclepias spp Milkweed beetle Chemical Compounds Plant Primary compounds Molecules necessary for normal growth and regulation. Plant Secondary compounds Molecules that help ensure plant survival. > Repellent > Kill or damage predator 10,000+ compounds are toxic to animals. Salicylates help plants detect and respond to infection. Willow family: Salicaceae Aspen (Populus) Cottonwood Willow (Salix) Balsam poplar 11

12 Talking Trees! Stones have been known to move and trees to speak -- Shakespeare s Macbeth Willows (Salix spp) wounded by insects produce an airborne chemical hydrocarbon ethylene Trees over 100 ft away sensed this and produced proanthocyanidin (an insecticide)! Research team: University of Washington in Seattle, led by Professor David F. Rhoades Dealing with Injury Compartmentalization - Survival mechanism 1) saps 2) resins 3) pitch Prevent invaders from spreading to other parts of the plant. Benefits to humans: Incense, rubber, pitch increases thermal output of burning wood. Lab This week: Read Pages in Lab manual Pre-lab assignment: P Turn in at the beginning of lab 12

13 Diffusion Diffusion: the movement of molecules down a concentration gradient From HIGH LOW concentration NO ENERGY required Diffusion: The Molecular Basis Brownian motion: Random movement of particles caused by inherent kinetic energy Robert Brown Movement is RANDOM, not directional Diffusion and Osmosis Water (Solvent) Selectively Permeable Membrane Solute 13

14 Osmosis: Activity Hypertonic Solution cell Osmosis: Activity Hypotonic Solution cell Osmosis: Activity Isotonic Solution cell 14

15 Plant Cell Animal Cell Plant Cell Animal Cell Plant Cell Animal Cell Osmosis: Plant and Animal Cells Hypotonic Isotonic Hypertonic Osmosis: Plant and Animal Cells Hypotonic Isotonic Hypertonic Osmosis: Plant and Animal Cells Hypotonic Isotonic Hypertonic 15

16 Plant Cell Animal Cell Osmosis: Plant and Animal Cells Hypotonic Isotonic Hypertonic Plasmolyzed Turgid 16