1. Ch. 4 Plant Physiology

2. Net flow in whole plants
Fig overview of transport in plants
Animation Transpiration Pull (animation ~ 5)

3. Some Key Concepts
Diffusion: movement of molecules from high to low concentration.
Osmosis: diffusion across a semi-permeable membrane.
Mass or bulk flow: movement of fluid due to pressure or gravity differences.

12. Long-distance movement of water
Plants mostly obtain water & minerals from soil.
Water moves up the xylem by bulk flow.
Movement of water depends on transpiration pull, cohesion & adhesion of water molecules, capillary forces, and strong cell walls.

13. Fig a

14. Fig b

15. Ascent of xylem sap transpirational pull
flow from greater to lower water concentration
relies on cohesion & adhesion of water
cavitation breaks chain of water molecules
corresponding overheads:
Fig roles of cohesion & adhesion in ascent of xylem sap
Fig control of stomatal opening & closing

16. Figure 35.11 Water-conducting cells of xylem

17. Other mechanisms of water transport not important.
Diffusion (note mosses, etc.)
Capillary forces
Osmotic pressure (guttation)

18. Fig

19. The availability of soil water and minerals
Animation (animation~4) Mineral uptake in roots
Long-distance transport of water from roots to leaves

20. Mineral Uptake Key Points
Mineral movement to root by diffusion or bulk flow or root growth.
Uptake controlled at root endodermis.
Uptake by either simple diffusion (no protein), facilitated diffusion (protein channel), or active uptake (requires energy and a protein carrier).
Organisms concentrate minerals and most other substances.
Usually biggest energy expenditure of roots, cause nutrients are being concentrated.

25. Movement of sugars Sugars (etc.) move from the source To the sink
Photosynthetic leaves
Storage organ
To the sink
Growing organs
Developing storage tissue
Through mass flow in phloem
Pressure Flow Hypothesis

26. Phloem transport pressure flow
high sugar concentration at “source”
sugar diluted with water from xylem creating pressure for flow
sugar unloaded at “sink” where it is metabolized or converted to starch
excess water flows to xylem back to “source”
translocation: movement of food from “source” to “sink(s)”
sinks may be new leaves, fruit, roots
Animation Transport (bulk flow model) - Animation ~ 6
associated overhead:
fig Pressure Flow in a sieve tube
Pressure flow in a sieve tube

27. Transport Movies

28. Some “hot” areas in plant water and nutrient research
Improving plant water-use efficiency
Improving salt tolerance
Improving nutritional value of plants (e.g., golden rice, increasing Fe content)
Phytoremediation

29. Life on Earth depends on flow of energy from sun

31. Life processes are driven by energy
Plants are dynamic metabolic systems
1000s of reactions occur every second
Processes can be
energy consuming (endergonic) or
energy releasing (exergonic) and
catabolic (breakdown) or
anabolic (synthesis)

32. Fig. 8.6

33. Fig. 8.7

35. The most common and important forms of cellular energy.
Chemical bonds (e.g., ATP, CH2O)
Electrons (redox reactions)
Electrochemical gradients

36. Fig. 8.14

38. Cellular respiration
Chemical-bond energy in sugars is converted to energy-rich compound ATP which can then be used for other metabolic reactions

44. Fig. 9.19

45. Energy yield depends on oxygen
Aerobic (with oxygen)
36 ATP molecules per glucose molecule
Anaerobic (without oxygen)
2 ATP molecules per glucose molecule