Lecture 3 Plant nutrition

1. Lecture 3Plant nutrition 3.4d

2. Plants develop extensive root systems

3. Different areas of the root absorb different mineral ions - absorption of calcium in barley is restricted to apical region - iron is taken up either at apical region (barley) or over entire root surface (corn) - potassium, nitrate, ammonium, phosphate are absorbed at all locations of the root - root apex absorbs ammonium more rapidly than elongation zone (corn, rice) - root hairs are the most active in phosphate absorption → strong demand of nutrients in apical region (cell elongation)

4. 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 penetrate the intercelluar spaces of the cortex to form the Hartig net - total mass of fungal hyphae may be comparable to the root mass itself

5. Association of vesicular-arbuscular mycorrhizal fungi - fungal hyphae grow into the intercellular wall spaces of the cortex and penetrate individual cortical cells - as they extend into the cell, they do not break the plasma membrane or the tonoplast of the host cell - instead, the hypha is surrounded by these membranes and forms structures known as arbuscules, which participate in nutrient ion exchange between the host plant and the fungus

6. 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