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TRANSPORT IN PLANTS

CHAPTER 36. TRANSPORT IN PLANTS. The algal ancestors of plants were completely immersed in water and dissolved minerals. Terrestrial adaptation: - roots: absorb water and minerals from the soil - shoots:exposed to light and atmospheric CO 2 .

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TRANSPORT IN PLANTS

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  1. CHAPTER 36 TRANSPORT IN PLANTS

  2. The algal ancestors of plants were completely immersed in water and dissolved minerals. Terrestrial adaptation: - roots: absorb water and minerals from the soil - shoots:exposed to light and atmospheric CO2. This morphological solution created a new problem: the need to transport materials between roots and shoots. Vascular tissues transport sap throughout the plant body. Introduction

  3. Transport in plants occurs on three levels: (1) the uptake and loss of water and solutes by individual cells (2) short-distance transport of substances from cell to cell at the level of tissues or organs (3) long-distance transport of sap within xylem and phloem at the level of the whole plant.

  4. Cell membrane is selectively permeable. Passive Transport: Simple Diffusion Osmosis Facilitated diffusion (transport proteins) Active Transport: need ATP energy Chemiosmosis (proton pump) Charge Gradient Cotransport Cell Transport Processes

  5. Simple Diffusion

  6. Osmosis Osmosis

  7. Facilitated Diffusion

  8. Passive Versus Active Transport Passive Versus Active Transport

  9. Chemiosmosis Chemiosmosis

  10. Charge Gradient Uses the attractive-repulsive properties of ions to move other ions across membranes

  11. Plant Cell Structure cell wall chloroplast nucleus central vacuole

  12. Cotransport Cotransport

  13. Water Relations of Plant Cells

  14. Differences in water potential drive water transport in plant cells

  15. Water Potential • Refers to the tendency of water to leave or enter the cell. • Measured in megapascals (MPa; y = 1MPa = 10 atm). • Measured relative to pure water in which y = 0 Mpa. • If solution draws water away from pure water then the water potential of the solution is less than 0 (y < 0). • If solution looses water to pure water then the water potential of the solution is greater than 0 (y > 0). • Water potential of a solution is a combined effect of solute concentration and pressure (or tension) on the system.

  16. Water Potential

  17. Water Potential

  18. Water Potential

  19. Water Potential

  20. Plasmolysis • cell shrinking

  21. Turgor Pressure • cell swelling

  22. Bulliform Cells

  23. Short-Distance VersusLong-Distance Transport

  24. Involves simple diffusion, osmosis and active transport. Routes Cell-to-Cell Across Cell Membranes Symplast (involves cytoplasm and plasmodesmata) Apoplast (transport through porous cell walls) Short-Distance Transport

  25. Involves transpiration and root pressure. Continuous tube of water depends upon water cohesion and adhesion. Long-Distance Transport

  26. Short-Distance Transport

  27. Long-Distance Transport

  28. Transpiration

  29. Guard Cells Mediate Transpiration Stomatal Opening and Closing

  30. Stomatal Opening and Closing

  31. Stomatal Opening and Closing

  32. Sugar LoadingintoSieve-tube Members

  33. Interaction Between Xylem and Phloem

  34. Guttation: root pressure forces excess water out of leaf Transpiration at night is low Roots accumulates minerals and ions, which build up root pressure Excess water is forced out of leaf

  35. Plants adapted to arid climates, called xerophytes, have various leaf modifications that reduce the rate of transpiration. Many have small, thick leaves, reducing s.a. A thick cuticle Waxy coat During the driest months, some desert plants shed their leaves, while others (such as cacti) subsist on water stored in fleshy stems during the rainy season Xerophytes have evolutionary adaptations that reduce transpiration

  36. In some xerophytes, the stomata are concentrated on the lower (shady) leaf surface. Trichomes (“hairs”) also help minimize transpiration by breaking up the flow of air, keeping humidity higher in the crypt than in the surrounding atmosphere. trichomes stomata

  37. Let’s see some TRICHOMES!

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