Plant Physiology Lecture Notes PDF

11/19/20 Lecture 25 Plant Physiology 1 11/19/20 Plant Growth Requirement • Plants are autotrophic – be able to survive in an inorganic environment • 17 essential nutrients are required for plant to complete its life cycle - From atmosphere: carbon dioxide - From soil: water, fertilizer...

11/19/20 Lecture 25 Plant Physiology 1 11/19/20 Plant Growth Requirement • Plants are autotrophic – be able to survive in an inorganic environment • 17 essential nutrients are required for plant to complete its life cycle - From atmosphere: carbon dioxide - From soil: water, fertilizer (N) (K) (Ca) (Mg) (P) (S) (Cl) (Fe) (B) (Mn) (Zn) (Cu) (Ni) (Mo) + Carbon (C), Hydrogen (H) and Oxygen (O) – component of carbohydrates, proteins, lipids and nucleic acids 2 11/19/20 Nutrient Deficiency Symptoms on Plants Iron deficiency: Interveinal yellowing on younger leaves Nitrogen deficiency: Uniform yellowing on older leaves Potassium deficiency: Purplish to reddish-purple leaves Plant Response to External Signals • Tropism: directional growth in a plant - Phototropism Gravitropism Hydrotropism Thigmotropism - • Nastic movement: non-directional response to stimuli - Nyctinasty Seismonasty - 3 11/19/20 Phototropism: plants bend toward the light to maximize the light intercept for photosynthesis Gravitropism: plants are oriented to the directionality of gravity - Positive in the root - Negative in the shoot Shoots grow upwards Roots grow downwards 4 11/19/20 Hydrotropism: the movement of a plant towards or away from water Toward water (drought) Away from water (flooding) 5 11/19/20 Thigmotropism: curling of climbing plants that responds to the stimuli of contact Lecture Activity: What tropism is shown here? Gravitropism Phototropism Hydrotropism Gravitropism Thigmotropism 6 11/19/20 Nyctinasty: associated with diurnal light and changes in temperature Day Night Prayer Plant (Maranta sp.) Dark Light Ranunculus sp. Buttercup 7 11/19/20 Seismonasty: occur in response to touch, wounding, and intense heat • Essential characteristics - Rapid - “All-or-none” response – not proportional to stimulus - Excitation is propagated from the point of stimulation Mimosa pudica L. (“shy” plant) 8 11/19/20 Venus’ Flytrap Sundew Pitcher Plants Video 9 11/19/20 Plant Growth Controlled by Internal Signals • Plant growth and development are regulated by plant hormones - Signal molecules produced at specific locations - Alter processes in target cells at local or other locations - Act in very low concentrations Auxin: 1st discovered; produced in the shoot apical meristem; associated with apical dominance 10 11/19/20 Christmas tree plant Cotton plant Gibberellin: enhance stem elongation; reducing its level would suppress vertical shoot growth 11 11/19/20 Cytokinin: produced in roots; stimulate cell division; delay leaf yellowing under environmental stress Grass grown under high temperature Control Cytokinin-treated Abscisic acid (ABA): produced in mature leaves; close the leaf stomata under water stress to preserve water Control ABA-treated 12 11/19/20 Ethylene: gas form; emitted from yellowing leaves and ripening fruits; stimulate leaf and fruit abscission e+™ (ethylene remover) 13 11/19/20 Lecture Activity: Plant Hormone Show and Tell Can you explain the use of hormones in this diagram? Fresh fruits are shipped around the world. Ethylene inhibitors are used to slow the ripening of the fruit, so they are just ripe as they reach the supermarket. Can you explain the use of hormones in this diagram? Gibberellin can be sprayed to increase internode length and grape size. 14 11/19/20 Which of the following statements is true? Gardeners prune to create bushier plants. This is because pruning causes plants to create... a. More auxin and this enables side shoots to grow b. Less auxin and this enables side shoots to grow c. More auxin and this inhibits side shoots from growing d. Less auxin and this inhibits side shoots from growing 15