Category: Plant Physiology Pro

Three carbon fixation strategies C3 plants (rice, wheat, most trees) fix CO₂ directly via Rubisco in mesophyll — simple but prone to photorespiration in heat. C4 plants (maize, sugarcane) shuttle CO₂ to bundle sheath cells, concentrating it around Rubisco — efficient in hot bright climates. CAM plants (cacti, pineapple) open stomata at night to fix…

Water deficit response Soil drying triggers ABA (abscisic acid) accumulation, closing stomata and inducing stress-protective proteins (dehydrins, LEA proteins). Osmotic adjustment Cells accumulate compatible solutes (proline, glycine betaine, sugars) to maintain turgor without toxic ion levels. Measurement Predawn leaf water potential with pressure chamber Stomatal conductance with porometer Soil moisture sensors at root zone depth…

Major plant hormones Auxin — cell elongation, apical dominance Cytokinin — cell division, shoot meristem activity Gibberellins — stem elongation, seed germination ABA — stress response, seed dormancy Ethylene — fruit ripening, senescence Brassinosteroids — growth, stress tolerance Cross-talk Hormones interact — shade (low R:FR) elevates auxin and reduces BR signaling, promoting elongation. Understanding networks…

Visual diagnosis Mobile nutrients (N, P, K, Mg) show symptoms on older leaves first as plant remobilizes them to new growth. Immobile nutrients (Ca, Fe, B) affect young tissue first. Common deficiencies Nitrogen — general chlorosis, stunting Iron — interveinal chlorosis on young leaves Potassium — marginal necrosis, weak stems Calcium — blossom end rot…

Stomata as valves Guard cells regulate pore aperture controlling CO₂ entry and water vapor loss. Balance between photosynthesis demand and drought stress drives behavior. Measurement Infrared gas analyzers measure net photosynthesis and transpiration simultaneously. Calculate intrinsic water use efficiency as A/E ratio. Environmental drivers Light, CO₂ concentration, humidity (VPD), and ABA signaling all modulate stomatal…

Day length sensing Short-day plants flower when nights exceed critical length (chrysanthemum, soybean). Long-day plants flower when nights are shorter than critical (spinach, Arabidopsis). Phytochrome mechanism Night length measurement via phytochrome Pr/Pfr interconversion. Interrupting dark period with flash of light can prevent or trigger flowering depending on species. Commercial use Greenhouse growers manipulate photoperiod with…