Plant Physiology
Photosynthesis, respiration, transport, source-sink relationships, hormones, stress responses, and whole-plant coordination.
Published lessons
These pages are organized here by subject. The permanent THC-ENC IDs remain stable behind the scenes even when a clearer display title is used.
Plant Cells, Tissues, and Organ Systems
Connect cell structure to dermal, ground, vascular, and meristematic tissues and explain why a whole-plant symptom must be localized before it is diagnosed.
Chloroplasts, Chlorophyll, and Light Capture
Explain how chloroplast structure and pigment organization capture light while separating leaf greenness from measured photosynthetic performance.
The Light Reactions of Photosynthesis
Trace excitation, water oxidation, electron transport, ATP formation, and NADPH production and relate excess excitation to photoprotection and injury risk.
Carbon Fixation and the Calvin Cycle
Explain how Rubisco fixes carbon dioxide in a C3 plant and why ATP, NADPH, stomatal supply, enzyme capacity, and product use jointly limit assimilation.
Net Photosynthesis Versus Gross Photosynthesis
Distinguish gross carbon fixation, leaf respiration, net CO2 exchange, and whole-crop carbon balance so that measurements are not mislabeled as yield.
Photorespiration and Temperature Stress
Explain Rubisco oxygenation, the photorespiratory recovery pathway, and why temperature stress cannot be reduced to a single universal leaf limit.
Cellular Respiration and Night Metabolism
Trace carbohydrate oxidation through glycolysis, the tricarboxylic-acid cycle, and mitochondrial electron transport and relate night conditions to carbon cost and crop function.
Stomata, Guard Cells, and Gas Exchange
Explain how guard-cell regulation couples carbon dioxide entry to water loss and interpret assimilation, conductance, transpiration, and internal CO2 together.
Xylem Transport and the Cohesion-Tension Mechanism
Trace water and mineral movement through xylem and explain how transpiration, hydraulic resistance, cavitation, roots, and environment shape supply to the canopy.
Phloem Transport and Sugar Allocation
Explain pressure-driven translocation from source to sink and use phloem logic to interpret growth, pruning, girdling, and organ competition.
Source Leaves and Sink Tissues
Classify changing source and sink roles and explain how sink strength, vascular connection, organ stage, and genotype influence allocation.
Leaf Area, Canopy Photosynthesis, and Self-Shading
Scale from a single leaf to a layered canopy and use leaf area, light distribution, leaf age, and spatial uniformity to evaluate productive canopy structure.
Plant Hormones: Auxin
Explain auxin synthesis, polar transport, concentration- and tissue-dependent responses, and its roles in apical dominance, tropisms, vascular development, and adventitious rooting.
Plant Hormones: Cytokinins
Explain cytokinin synthesis, transport, cell-division and shoot-development roles, and why cytokinin effects depend on auxin balance, genotype, tissue, and nutrient status.
Plant Hormones: Gibberellins
Explain gibberellin control of elongation, germination, developmental transitions, and reproductive traits while separating endogenous signaling from chemical treatment claims.
Plant Hormones: Ethylene
Explain ethylene synthesis, perception, transport, and interactions with growth, senescence, abscission, stress, and cannabis reproductive expression.
Abscisic Acid and Water-Stress Signaling
Explain abscisic-acid synthesis, transport, guard-cell action, growth regulation, and stress memory without treating ABA as a direct measurement of drought severity.
Jasmonates, Salicylates, and Defense Signaling
Explain jasmonate and salicylate signaling, defense crosstalk, growth costs, and why elicitor claims require organism-, tissue-, dose-, and outcome-specific evidence.
Growth Rate, Development, and Biomass Partitioning
Separate size, growth rate, developmental stage, and allocation and calculate interpretable plant and crop performance metrics.
Genotype-by-Environment Effects on Physiology
Design comparisons that separate genetic, environmental, and genotype-by-environment effects and avoid turning one cultivar response into a universal cannabis rule.