Lecture 8 Plant nutrition

1. Lecture 8 Plant nutrition

2. Essential Elements Essential elements: macronutrients and micronutrients

3. Essential Elements Essential elements: macronutrients and micronutrients

4. Classification of nutrients according to their biochemical function

5. Classification of nutrients according to their biochemical function

6. Classification of nutrients according to their biochemical function

7. Special techniques are used in nutritional studies - roots immersed in nutrient solution - large volume of nutrient solution and adjustment required - oxygen supply, bubbling - roots receive ample supply of oxygen

8. Special techniques are used in nutritional studies - roots suspended in air while being sprayed continuously with a nutrient solution - easy manipulation of gaseous environment - requires larger amounts of nutrients vs. hydroponics - roots are periodically immersed in nutrient solution - requires higher levels of nutrients vs. hydroponics

9. The Role of Chelators in nutrient solution Problem with nutrient solutions is maintaining the availability of iron due to precipitation of iron out of the solution. Add chelators that form complexes with cations (Fe, Ca) in which cation is held by ionic forces rather than covalent bonds. Chelated ions remain physically available for the plant. Diethylenetriaminepentaacetic acid (DTPA) DTPA chelated to an Fe3+ ion that binds through N atoms and three ionized O atoms; Resulting ring structure clamps the Fe

10. Mineral deficiencies disrupt plant metabolism and function Inadequate supply of an essential element results in nutritional disorder manifested by characteristic deficiency symptoms Group 1: Deficiencies in mineral nutrients that are part of carbon compounds (N, S) Group 2: Deficiencies in mineral nutrients that are important in energy storage or structural integrity (P, Si, B) Group 3: Deficiencies in mineral nutrients that remain in ionic form (K, Ca, Mg, Cl, Mn, Na) Group 4: Deficiencies in mineral nutrients that are involved in redox reactions (Fe, Zn, Cu, Ni, Mo) For more examples on nutrient deficiencies, please visit http://3e.plantphys.net/article.php?ch=t&id=289

11. Nitrogen deficiency Symptoms - stunted - older leaves or whole plants yellowish green - sometimes all leaves become light green and chlorotic at the tip - leaves die under severe N stress - all leaves are narrow, short, erect, and lemon- yellowish green except for young leaves, which are greener - entire field may appear yellowish - reduced tillering - reduced grain number Tomato Corn

12. Phosphorus deficiency Symptoms - plants are dwarfed or stunted - plants develop very slowly in relation to other plants growing without phosphorus deficiency - some species such as tomato, lettuce, corn and crucifers develop a distinct purpling of the stem, petiole and the undersides of the leaves - under severe deficiency conditions, there is also a tendency for leaves to develop a blue-gray luster - in older leaves under very severe deficiency conditions, a brown netted veining of the leaves may develop - necrotic spots = small spots of dead tissue Cabernet sauvignon grapes, CA Corn

13. Potassium deficiency Soybean Symptoms - mottled or marginal chlorosis, which then develops into necrosis on tips, margins and between veins - symptoms initially on more mature (“older”) leaves - leaves may curl and crinkle - stems may be slender and weak, with abnormally short internodal regions - in K-deficient corn, nodes may have increased susceptibility to root-rotting fungus present in the soil - this together with stem weakness results in bending of stems to the ground (lodging) Corn

14. Iron deficiency Symptoms - strong chlorosis at the base of the leaves with some green netting - deficiency starts out with interveinal chlorosis of the youngest leaves, evolves into an overall chlorosis, and ends as a totally bleached leaf - bleached areas often develop necrotic spots - because iron has a low mobility, iron deficiency symptoms appear first on the youngest leaves - iron deficiency is strongly associated with calcareous soils and anaerobic conditions, and it is often induced by an excess of heavy metals Tomato

15. Analysis of plant tissues reveals mineral deficiencies

16. Influence of the pH on the availability of nutrient elements in organic soils - main losses of nutrients from agricultural systems due to leaching that carries dissolved ions, especially nitrate, away with drainage water - in acid soils, leaching may be decreased by the addition of lime – a mix of CaO, CaCO3 and Ca(OH)2 – to make the soil more alkaline, because many elements form less- soluble compounds when the pH is higher than 6 - width of the shaded areas in the graph indicates the degree of nutrient availability to the plant root

17. Inorganic fertilizer… Straight fertilizer…Super phosphate, ammonium nitrate Compound fertilizer (i.e. contain two or more mineral nutrients) Organic fertilizer Residues of plants and animals Mineralization (organic compounds broken down by microorganisms) Treating nutritional deficiencies

18. Uptake is faster Deficiency can be prevented Not tied up in soils (Fe, Mn and Cu) Expensive Vineyards Foliar application of fertilizers

19. Plants develop extensive root systems Wheat Fibrous Root System Tap Root System

20. Different areas of the root absorb different mineral ions - depends on plant species - Fe is taken up either at apical region (barley) or over entire root surface (corn) - K, NO3¯, NH4+, P absorbed at all locations of root - root hairs are most active in P absorption - strong demand of nutrients in apical region (cell elongation)

21. Root infected with ectotrophic mycorrhizal fungi Example: only tree species; gymnosperms and woody angiosperms - fungal hyphae surround the root to produce a dense fungal sheath and pene- trate the intercelluar spaces of the cortex to form the Hartig net - total mass of fungal hyphae may be comparable to the root mass itself

22. Association of vesicular-arbuscular mycorrhizal fungi to promote P acquisition Example: Alfalfa - fungal hyphae grow into the intercellular wall spaces of the cortex and penetrate individual cortical cells - plasma membrane or tonoplast of host cell does not break - instead, the hypha is surrounded by these membranes and forms arbuscules, which partici- pate in nutrient ion ex- change between the host plant and the fungus

23. Nutrition - Summary - macro- and micronutrients are essential for plant life - nutritional disorders occur because nutrients have roles in energy storage, plant structure, enzyme cofactors, electron transfer reactions - mineral nutrition can be studied through the use of solution culture - to prevent development of deficiencies, nutrients may be added back to the soil/plant through fertilizers - size of soil particles and cation exchange capacity determine the reservoir for water and nutrients - soil pH affects availability of mineral elements to plants - plants develop extensive root system to obtain nutrients - plant roots form associations with mycorrhizal fungi - hyphae facilitate the acquisition of mineral elements (P) - in return, plants provide carbohydrates to mycorrhizae