Chapter 10 – Transport in Plants

1. Chapter 10 – Transport in Plants

2. Transport in plants • Water and mineral nutrients must be absorbed by the roots and transported throughout the plant • Sugars must be transported from site of production, throughout the plant, and stored

3. Cellular transport mechanisms

4. Osmotic potential, solutes, and water movement

5. Water potential influences water movement • Water potential (Ψ) of a cell: Ψcell = ΨΡ + ΨΟ Ρ = pressure potential Ο = osmotic (solute) potential

6. Ψp - Pressure potential (turgor) Low Ψp High Ψp

7. ΨΟ– Osmotic (Solute) potential • Pure water ΨΟ= 0 • All solutions, ΨΟ< 0 • As solute concentration increases, Ψcell …

8. Water movement in plants • Movement from high Ψcell to low Ψcell • Occurs in the xylem • Involves adhesion, cohesion, and pressure

9. Adhesion and cohesion

10. Water transport

11. Tension-cohesion theory explains xylem transport • Water is drawn up the plant by transpiration of water from stomata

12. A water potential gradient creates tension

13. higher ψ higher ψ Transpiration creates tension lower ψ lower ψ cohesion lower ψ higher ψ highest ψ higher ψ low ψ

15. Water transport animation

16. Transpiration & water transport

17. Importance of stomata • Regulate transpiration rate • Controls rate of water uptake • Water required for photosynthesis • Water required to maintain turgor pressure • Influences nutrient uptake • Regulate gas exchange • CO2 required for photosynthesis

18. Turgid guard cells open stomata

19. Guard cells & osmotic potential

20. Transpiration & photosynthesis

21. Ψ and transpiration rate • In terms of ψ, can you explain how transpiration rate is influenced by: • Atmospheric humidity? • Wind? • Air temperature? • Light intensity?

23. Which of the following explains why water moves into the root from the soil? • The water potential of the root is lower than the water potential of the soil • The roots exist in a hypertonic environment • The pressure potential of the soil forces water into the root • Water is actively transported into the root • The soil has a higher solute concentration than the roots, causing water to diffuse into the roots

24. Stomata close when • Photosynthesis lowers CO2 concentrations in the leaves • Potassium ions are pumped into guard cells • Abscisic acid levels increase • Guard cells become turgid • All of these occur

25. A guard cell with a high internal concentration of K+ • Is in a hypertonic condition • Has a low water potential relative to outside of the cell • Has a higher water potential than outside the cell • Both 1 and 2 • Both 2 and 3

26. Water transport

27. Sugar transport

28. Source to sink sugar transport

29. Pressure-flow hypothesis explains sugar transport

30. Phloem loading

31. Sugar transport can be explained by water potential

32. Transport in plants • Water and mineral nutrients are absorbed by the roots and transported throughout the plant by tension-cohesion • Sugars are transported from site of production (source), throughout the plant, and stored (sinks) by pressure-flow

33. Mineral nutrition & uptake

34. Soils and plant nutrition • 14 essential mineral nutrients • N,P,K,S,Ca,Mg,Fe,Cl,Mn,B,Zn,Cu,Mo,Ni • 3 essential non-mineral nutrients • C,H,O • What makes these nutrients essential?

35. Magnesium and photosynthesis

36. Nitrogen and amino acids

37. Nitrogen, phosphorus & DNA

38. Potassium and cell function

39. Macronutrients vs. micronutrients

40. Fertilizers • Fertilizer analysis (N-P-K) • Analysis varies depending on growth objectives

43. How can essential elements be determined?

44. Hydroponics

46. Recreational hydroponics • Home hydroponics systems

47. A soil profile • Soil composition • Sand, silt, clay • Humus • Microorganisms • Animals

48. Mineral nutrients exist as ions

49. Cation exchange allows mineral ions to be absorbed by roots

50. Cation exchange and H+