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Plant bio
Phosphorus
| Question | Answer |
|---|---|
| Phosphorus | - P has roles in cell structure, energy and information storage and energy and information transfer - 1st or 2nd most commonly limiting nutrient for plant growth - essential nutrient found in many biomolecules ie. DNA/teeth - rare macronutrient |
| Global phosphorus cycle | - no atmospheric phosphorus - weathering of P from rocks to soil - terrestrial cycle (plants, animal, soil) - leaching of P into bodies of water |
| Human influence on phosphorus cycle | - mining and commercial processing - increased sewage and runoff to bodies of water, increasing algal blooms (toxic) - modern practices accelerate runoff |
| Phosphorus in soil | - found in form of insoluble complexes - plants can't take up organic phosphate - depletion zone: only P close to roots is taken up |
| Phosphate use in agriculture | - consumption of P majorly increased due to population increase - crops only take up 50-70% applied P fertiliser - overuse was common, but now N:P ratio is 1:6 (better) |
| pH | - phosphate availability varies with pH - optimum soil pH is 6 for available phosphates |
| Eutrophication | - increased biomass production (leads to algal blooms) - decreased O2 concentrations - ecosystem collapse |
| Consequences of P limitation | - sufficient P: green leaves (chlorophyll) - low P: darker/red leaves (lacks chlorophyll) |
| Phosphate uptake systems: root structure | - nutrient accumulation requires uptake across plasma membranes - PMs of root cells are selective and determine what enters the shoot |
| Plant phosphate transporters | - Pht proteins: localised to PM and uptake at root - co transporters acquire Pi from rhizosphere (soil) - Pht2&3 localised to organelles (chloroplast/mitochondria) - Pht1 mediate uptake and transport |
| Rhizosphere pt.1 | - plants engineer their rhizosphere - root exudes, organic acids and proteins - many species respond to nutrient deficiency - low pH helps solubilise these nutrients |
| Rhizosphere pt.2 | - carboxylates complex to metal ions that bind to phosphate by ligand exchange - H+ secretion can balance charge |
| Acid phosphates | - promote uptake of organic P In response to P deficiency the roots of many species secrete acid phosphatases, which solubilise Pi from organic P-esters |
| Root system architecture | root traits associated with enhanced phosphate uptake: - reduced gravitropism (roots slump) - formation/elongation of roots - aerenchyma (air spaces allowing metabolically inexpensive growth |
| P deficiency | - influences rooting depth and branches pattern - low P causes shallow roots, attempting to find higher P concentrations in the soil: root foraging - increased density and length |
| Root hairs | - projections of trichoblast cells - increases root surface area - increase the volume of nutrient depletion zone |
| Symbioses: AM fungi | - plants use AM fungi network to increase the effective reach of the roots - facilitates P uptake in most plants AM: 450+ MYA symbioses, surrogate roots for first land plants, main role thought to be P uptake |
| AM and role in P exchange | - plant releases strigolactones, that affects hyphal growth - fungi enters the plant, forming a branched structure (arbuscule) - sites of exchange from sugars to nutrients - data suggests Pi is translocated through fungal hyphae as polyphosphate |
| PT4 | - located on the periarbuscular membrane, a phosphate transporter |
| Legume symbiosis | - legumes can form symbioses with AM fungi and legume-Rhizobium - many similarities between the two |
Created by:
reub8n
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