Plant Biology All Topics Review

Flashcards covering plant biology topics including photoreceptors, photosynthesis, nutrient assimilation, stress responses, and programmed cell death.

Photoreceptors in Plants

Plants use phytochromes (red/far-red), cryptochromes (blue), and phototropins (blue/UVA) to regulate development.

Photosynthesis vs. Photomorphogenesis

Photosynthesis generates chemical energy, while photomorphogenesis optimizes plant structure for light capture.

Phototropism

Directional growth of a plant toward a light source.

Shade Avoidance

Stem elongation in response to far-red light competition.

Photosystem II (PSII)

Splits water, releasing O₂ and electrons during the light reactions of photosynthesis.

Photosystem I (PSI)

Transfers electrons to NADP⁺, forming NADPH during the light reactions of photosynthesis.

ATP Synthase

Generates ATP during the light reactions of photosynthesis, fueling carbon fixation.

Linear Electron Transport

Produces ATP, NADPH, and O₂ using both PSII and PSI during photosynthesis.

Cyclic Electron Transport

Produces only ATP, recycling electrons within PSI during photosynthesis.

Calvin-Benson Cycle

Involves Carboxylation (CO₂ fixation), Reduction (G3P formation), and Regeneration (RuBP recycling) in carbon fixation.

PEP Carboxylase

Captures CO₂ efficiently in the C4 cycle, reducing photorespiration and benefiting plants in hot climates.

Nitrogen as a Limiting Nutrient

Nitrogen must be converted from N₂ to NH₄⁺ or NO₃⁻ for plant use, making it dependent on biological fixation.

Sulfate Assimilation

SO₄²⁻ is activated into APS, APS is reduced to sulfite, then sulfide, and sulfide is incorporated into cysteine, fueling protein synthesis.

Oxidative Stress

Condition caused by ROS (superoxide, hydrogen peroxide, hydroxyl radicals) leading to lipid peroxidation and DNA damage, disrupting cell stability.

Antioxidant Defense Systems

Enzymes (SOD, CAT, APX) and non-enzymatic antioxidants (carotenoids, flavonoids, glutathione) neutralize ROS.

Phenolics in Plant Defense

Reinforce cell walls against pathogens as secondary metabolites.

Alkaloids in Plant Defense

Disrupt herbivore metabolism as secondary metabolites.

Terpenoids in Plant Defense

Repel predators and stabilize membranes in heat stress as secondary metabolites.

Cyanogenic Glycosides

Release hydrogen cyanide (HCN) upon herbivore attack, inhibiting respiration and preventing grazing.

Programmed Cell Death (PCD)

Regulated apoptosis-like cell death in plants.

Necrosis

Uncontrolled cell collapse in plants.

Senescence

Gradual aging via ethylene in plants.

PCD in Plant Development

Tracheary element differentiation, leaf senescence, and oil channel formation rely on PCD for functional adaptation.