MINERAL NUTRITION & STRESS TOLERANCE Stress conditions : 1. Cold stress 2. Drought stress/Water logging (Water deficit + high temp.) 3. Salt stress 4. Deficiency stress

5. Chemical stress/Pollution 6. Photostress Over = Stress Optimum Under = Stress * Water/Temperature/Ion/Gas

1. Water stress - Water deficit - Water logging

Water Deficit (Plant response to :) - Stomata close Pn, Tr - Cell & Leaf expansion - Cell Turgidity - ABA, Respiration, Sugar, Proline - Ion toxicity (Salt stress)

N - increase LAI, shoot/root ratio (Less N - supply, ABA increase better WUE) P - deficiency increase ABA by water shortage faster than P - Sufficient Effect of Mineral Nutrition

K - Osmoregulation - Stomatal movement - Turgidity & Enzyme activity Na + - Partly replace K + Indirect effect on salinity

Waterlogged & flooded soil 1) disappearance of O 2 2) NO 3 - reduced to NO 2 - N 2 O N 2 3) MnO Mn 2+ exchangable & toxic 4) Fe 2+ Fe 3+ availability increase & toxic Anaerobic & reduction process cause :

5) increase P solubility 6) SO 4 = H 2 S decrease solubility of Fe, Cu, Zn, Cd 7) ethylene, volatile fatty acid & phenolics compound accumulate from decomposable organic manure

Symptom 1. Wilting (ethylene accumulation decrease of water permeability of root) 2. Lower leaf senescence (N - deficiency) 3. Lowering nutrient uptake Nutrient deficiency 4. Inhibit Cyt. & GA synthesis and transport but promote ethylene synthesis in leaves 5. Acetaldehyde & ethanol formation - Toxins

Tolerance : - O 2 - supply from shoot - Diminish ethylene formation

MINERAL NUTRITION & WATER BALANCE Water balance = water uptake transpiration 1. Water Uptake affected by ion concentration in soil solution & root - Osmotic Potential difference - Salt stress

2. Transpiration - Stomatal movement & K + translocate into guard cell - More K fertilizer => low transpiration, More proline drought resistant

2. Temperature Stress - Q10 and enzyme activity - Membrane permeability & ion uptake Cold temperature : inactivation of membrane bound enzyme, i.e. respiratory enzyme in MT respiration

cold temp. also disrupt water and ion uptake activity of root Frost cell dehydration protein denatured cell wall cracked

High temperature - Commonly combine with water stress (high transpiration rate) - PS = the most temperature sensitive (Chloroplast, Enzyme, Membrane) PS ll - Tolerance = Chloroplast, PS ll, Protein Stability

3. Mineral Stress - Over supply - salt stress - Deficiency Nutrient efficiency : - genetic control - growth stage/rate - mycorrhiza - soil condition (pH, ion concentration)

Soil condition & mineral stress 1. Acid mineral soil (pH < 4) - excess Al & Mn - deficiency of P Ca & Mg - some cases low S K Mo Zn Cu Al - toxicity = main limiting factor for growth until pH~5.5

Al - toxicity - inhibition of cell division at root apical meristem - interfier P - uptake (AlPO 4 ) - inhibit Mg -, Ca - uptake (ion competition)

Mn - toxicity - directly effect the shoot - inhibit Ca & Mg uptake - Liming to increase pH - Foliar application

2. Alkaline soil pH > 7 (Calcareous soil) CaCO 3 N = main growth - limiting factor - Fe Fe(OH) 2 +, Fe(OH) 3 - Zn - P Mn B

3. Saline Soil (Na +, Cl - ) - high salt concentration - high osmotic pressure - water deficit, ion excess - stomata close - small leaves, low Pn

- Respiration increase - less protein synthesis - Na + complete Ca 2+ - Cl - complete NO 3 - /P synergized The end