Mineral Nutrition

1. Mineral Nutrition

2. Mineral Nutrition - Overview • Some minerals can be used as is: • e.g. • Some minerals have to be incorporated into other compounds to be useful: • e.g. • Some minerals compounds have to be altered to be useful:

3. Chemical composition of plants • 80–85 % of an herbaceous plant is water. • Water is a nutrient since it supplies most of the hydrogen and some oxygen incorporated into organic compounds by photosynthesis. • Water also is involved in cell elongation and turgor pressure regulation

4. Chemical composition of plants: dry weight • 95% “organic” – • 5% inorganic minerals

5. Fig 37.2

6. Essential Nutrients • = • 2 types: macronutrients & micronutrients

7. Macronutrients • = CHOPKNS CaMg

8. Micronutrients • = elements required by plants in relatively small amounts (<0.1% dry mass). • Major functions: • Optimal concentrations highly species specific • FeBCl MoCuMnNi Zn

9. Mineral Deficiency • Not common in natural populations. Why? • Common in crops & ornamentals. Why? • Deficiencies of N, P, and K are the most common. • Shortages of micronutrients are less common and often soil type specific. • Overdoses of some micronutrients can be toxic.

10. Fig 37.4

11. Soils • What do soils give to plants??

12. Soil properties influence mineral nutrition • Chemistry – determines which minerals are present and available, thus affecting plant community composition • Physical nature – • Soil organisms – • Nitrogen! The only mineral that the plant can ONLY get from reactions mediated by soil organisms.

13. Soil texture & composition • Soil created by weathering of solid rock by: • Topsoil: mix of weathered rock particles & humus (decayed organic matter) • Texture: sand, silt, clay Large, spaces for water & air Small, more SA for retaining water & minerals

14. More about topsoil….. • Bacteria, fungi, insects, protists, nematodes, & • Earthworms! • Humus: • Bacterial metabolism recycles nutrients

15. Availability of soil nutrients • Cations in soil water adhere to clay particles (negatively charged surface) • Humus – negatively charged & holds water & nutrients. Thus very important in the soil!!!!!

16. Soil conservation • Natural systems: decay recycles nutrients • Fertilizers: N:P:K • Synthetic: plant-available, inorganic ions. Faster acting. • Problem: • Organic: slow release by cation exchange, holds water, thus less leaching

17. Why nitrogen? • Air is 80% Nitrogen, but….. • Macronutrient that is most often limiting. Why? • What’s it used for?

18. The Nitrogen Cycle N2 N2 fixation Denitrification Uptake Decomposition NO3 Nitrification Ammonification NH4 Organic N Leaching Immobilization

19. Nitrogen Fixation • conversion of N2 in air to NH3 by microbes

20. But N is also lost…. • Leaching – • Denitrification – conversion of NO3- back to N2

21. All steps within the soil are mediated by bacteria!!!! Fig 37.9

22. Nitrogen Fixation • is catalyzed by the enzyme nitrogenase. • Requires energy (ATP) • 3 ways: • Lightening – • Non-symbiotic – • Symbiotic

23. Symbiotic Nitrogen Fixation • Legumes: peas, beans, alfalfa • Plant – gets ample inorganic N source • Bacteria – gets ample carbon source

24. Fixation in Nonlegumes • Here in the NW: alder • Azolla (a fern) contains a symbiotic N fixing cyanobacteria useful in rice paddies. • Plants with symbiotic N fixers tend to be first colonizers. Why?

25. Nutritional Adaptations of Plants • Parasitic Plants • Carnivorous plants • Mycorrhizal relationships

26. 1. Parasitic plants • . • Ex. Mistletoes on Doug Fir & Ponderosa pine • Ex. Indian pipe – parasite on trees via mycorrhizae

27. Fig 37.15

28. http://www.nofc.forestry.ca/publications/leaflets/mistletoe_e.htmlhttp://www.nofc.forestry.ca/publications/leaflets/mistletoe_e.html

29. http://cals.arizona.edu/pubs/diseases/az1309/

30. 2. Carnivorous plants • Digest animals & insects – why? • Motor cells! • Ex. Venus flytrap, pitcher plant, Darlingtonia

31. 37.16

33. 3. Mycorrhizal relationships • Plants get greater SA for water & phosphorus uptake • Almost all plant species!

34. Fig 37.12

35. Three levels of transport in plants: • Cellular – • Short-distance – • Long-distance – throughout whole plant (xylem & phloem)

36. Transport at the Cellular Level • Diffusion = ? • Osmosis – • (i.e. water always acts to dilute)

37. Examples of Short Distance Transport • Absorption of water & minerals by roots

38. Guard cells • control stomatal diameter by changing shape. • Lose water, become flaccid, stomata close

39. Guard cells • Opening Mechanism: • Sunlight, circadian rhythms, & low CO2 concentration in leaf air spaces stimulate the proton pumps & thus stomatal opening

40. Guard cells • Closing mechanism: • Stomatal closure during the day stimulated by water stress – not enough water to keep GCs turgid

41. Fig 36.15

42. Motor Cells • Motor cells are the “joints” where this flexing occurs. • Accumulate or expel potassium to adjust their water levels & thus turgidity. • Oxalis – leaves fold in sunlight to minimize transpiration; open in shade • Transpiration = loss of water vapor from the stomata

43. Absorption of water & minerals by roots • Soil solution moves freely through epidermal cells & cortex • Endodermis – selective barrier to soil solution between cortex & stele. Sealed together by the waxy Casparian strip – • Once through the endodermis, soil solution freely enters the xylem

44. Fig 36.9

45. Mechanisms of Long Distance Transport • Xylem: • Phloem: Pushing pressure of water at one end of the sieve tube forces sap to the other end of the tube (= bulk flow).

46. Transport of xylem sap • Pushed by root pressure • Stele has high concentration of minerals. Water flows in, creating pushing pressure

48. Pulling xylem sap • Transpiration – cohesion – tension mechanism • Transpirational pull:

49. Ascent of xylem sap against gravity • Aided by: • Adhesion of water to hydrophyllic cell walls of the xylem, • Diameters of tracheids & vessel elements are small, so lots of surface area for adhesion

50. Control of Transpiration • Guard cells! – balance two contrasting needs of the plant: