Intercellular Transport in Plants

1. Intercellular Transport in Plants Page 828 - 851

2. So how do trees get water all the way to the top?e.g., > 100m !

3. Water potential =  •  of pure water = 0 • Measured in pascal or megapascal (MPa) • force per unit area • Auto tires and plumbing ~ 0.2 MPa • Other solutions with solute in it have a lower water potential (expressed as a negative) the greater the p, the lower (more - ) the  • Water always moves from high to low water potential

4. Remember: the water potential of pure water = 0 while that of solutions is always negative If you add solute to a solution, the water potential gets more negative!

5. Water potential -  •  of pure water = 0 • Measured in pascal or megapascal (MPa) • force per unit area • Auto tires and plumbing ~ 0.2 MPa • Other solutions with solute in it have a lower water potential (expressed as a negative) the greater the p, the lower (more - ) the  • Water always moves from high to low (more negative) water potential

6. Pascal and psi • Psi is 1 pound of force per square inch. • Pascal equals to a force of 1 Newton per square meter. • 1 Psi = 6,894.75729 Pascals (pa) • Gas pressure is + pa • Solute concentration pressure is - pa

7.  has two components • Solute potential (s) due to dissolved solutes • Water moves due to osmosis • [Solute] in a solution • Pressure potential (p) • Water moves due to pressure

8. Fig 37.3

9. Fig 37.1a

10. Fig 36.1b

11. Fig 37.3

12. Lost your turgor pressure?

13. Fig 37.4

14. Water enters roots from soil  of soil ~ - 0.3 mPa of cytoplasm in roots ~ - 0.6 mPa Due to solutes in plant cell cytoplasm

15. Fig 37.7: water has to pass through several layers to reach vascular tissues.

16. Fig 37.8: importance of Casparian Strip (suberin) The Point: to block entry of Na+ & other undesired solutes

17. So how does water now get to the top of the tree?

18. Properties of Water • Surface tension • Cohesion • Adhesion • Capillary action • Meniscus

19. Fig 37.11: Cohesion-tension theory of water movement in trees.

20. Fig 36.11: Cohesion-tension theory

21. Evidence?

22. Evidence?

23. Plant Signal Molecules, e.g., Abscisic Acid

24. Plant Signals Fig 39.30; Page 879

25. Plant Signals Fig 39.30; Page 879

26. Stomata Opening Guard cells change shape in response to ion and water flow

27. Stomata Opening Guard cells change shape in response to ion and water flow

28. Stomata Closing In response to dry conditions and mediated by release of ABA from roots and transport to leaves.

29. Stomata Closing

30. See text for other details supporting the Cohesion - Tension theory

31. Halophytes: surviving in the salt marsh (low water potential) • Add sugars and other non-toxic organics to the cytoplasm. Why? • Have specialized structures on their leaves to excrete (active transport) a solution with high [NaCl]! • See Box 37.1 on page 815!

32. Moving fluid • Must move water or body fluids over cells to provide continuous P for O2 and CO2 diffusion • Body fluids in multicellular organisms must be moved between air contact surface (e.g., lungs or gills) and tissues

33. Moving fluid • Fluid flows due to P • Organisms have evolved muscular organs and tissues to work as a pump • Remember: a pump has two parts to each stroke • Intake due to negative pressure • Output due to compression and + pressure

34. Open, Low DP Circulatory System

35. Open Circulatory System Ostia

36. Open circulatory systems • Low pressure system = low flow rates • Low energy requirements to move blood • Blood or hemolymph flows into spaces directly around tissues • Minimum diffusion distance! • Blood cannot be directed to tissues with high O2 demand • Only some of the blood gets aerated!

37. Why can insects utilize an ‘open’ circulatory system, but you cannot? Exoskeleton Size (vs. gravity) Metabolic rate Pressure!!!

38. Closed Circulatory Systems • High pressure differences in a closed system = high flow rates • Two types of capillary beds for gas exchange • Respiratory surface and tissue capillaries • Density of capillaries is proportional to activity of the tissue • Minimize diffusion distance! • Blood can be directed to tissues with high O2 demand

39. POISEUILLE’S LAW Q (flow)= Pr4 8  L Q = ml/min P = pressure difference r = radius of vessel(s) in a parallel system of pipes  = viscosity of fluid L = length of system

40. Evolutionary Perspectives • Closed Systems have evolved in both invertebrates and vertebrates • Annelids (earthworms) • Intense muscular activities • Use moist skin as respiratory surface • Requires high flow rates and respiratory pigment

41. Closed System Design • Pump (two cycles per stroke!) • Muscular arteries to maintain high pressure • Control radii of vessels for distribution of blood • Distensible veins to hold quantities of blood

42. Fig, 44.15b

43. Fig. 44.22

46. http://www.nytimes.com/2000/04/21/us/ scientists-say-they-have-found-the-heart-of-a-dinosaur.html http://dsc.discovery.com/news/2009/04/01/ long-necked-dino.html

48. Blood flow to the brain of a giraffe?

49. Blood flow to the brain of a giraffe? • Upright: Blood flow to the brain is via high pressure with thick arteries and veins • MAP = 193 mm Hg • MAP at head = 131 mm Hg • What about when the giraffe lowers its head to drink?