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Plant Responses to the Environment, Transpiration, Photosynthesis, Respiration

Plant Responses to the Environment, Transpiration, Photosynthesis, Respiration. Adapted from. 45.1 What Are Some Major Plant Hormones? . Plants respond to their environment in sophisticated ways React to stimuli like touch , gravity, moisture, light, and day length

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Plant Responses to the Environment, Transpiration, Photosynthesis, Respiration

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  1. Plant Responses to the Environment, Transpiration, Photosynthesis, Respiration Adapted from

  2. 45.1 What Are Some Major Plant Hormones? • Plants respond to their environment in sophisticated ways • React to stimuli like touch, gravity, moisture, light, and day length • They use hormones—chemicals that are secreted by cells and transported to other cells, where they exert specific effects

  3. 45.1 What Are Some Major Plant Hormones? • Auxins promote or inhibit elongation in different target cells • Controls positive phototropism (growth toward light) in shoots and gavitropism (growth toward or away from gravity) in shoots and roots

  4. Radish Seedlings Show Positive Phototropism Fig. 45-3

  5. Positive Gravitropism Auxin is transported to the lower side of the shoot, where it stimulates cell elongation and causes the stem to bend upward Auxin is transported to the lower side of the root, where it inhibits cell elongation and causes the root to bend downward (b) The shoot and root are oriented horizontally Fig. 45-2b

  6. 45.1 What Are Some Major Plant Hormones? • Gibberellins are primarily active in plant shoots • Promote stem elongation by increasing both cell division and cell elongation

  7. 45.1 What Are Some Major Plant Hormones? • Ethylene is a gas • Recognized as a plant “stress hormone” • Causes certain fruits to ripen

  8. Ripe Fruit Become Attractive to Animal Seed Dispersers Fig. 45-11

  9. 45.1 What Are Some Major Plant Hormones? • Abscisicacid helps plants withstand unfavorable environmental conditions • Causes stomata to close when water is scarce • Promotes root growth and inhibits stem growth under dry conditions • Maintains dormancy in seeds

  10. 45.1 What Are Some Major Plant Hormones? • Florigenscontrol the timing of flowering in response to environmental cues

  11. 45.2 How Do Hormones Regulate Plant Life Cycles? • Some plants display thigmotropism, a directional movement or change in growth in response to touch

  12. A Rapid Response to Touch Fig. 45-14

  13. A Sundew with Its Insect Prey Fig. 45-14

  14. Photosynthesis Review Occurs in two steps: • Light reaction and dark reaction (Calvin Cycle)

  15. Light Reaction • Requires light • Converts light energy into chemical energy (NADPH and ATP)

  16. Dark Reaction • AKA Calvin cycle • Does not require light • Makes sugar from CO2 and hydrogen ions carried by NADPH • Energy to do this comes from ATP produced in light reaction

  17. C4 and CAM plants separate light and dark reactions

  18. Cellular respiration in plants? • Yes! • Sugar must be converted into ATP for cells to use • Sugar + O2  CO2 + H2O + ATP • In mitochondria

  19. Transpiration • Plants breathe! • Gas exchange occurs through stomata • Evaporation from leaves (transpiration) draws water up the plant – like a straw! • Relies on cohesion and adhesion

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