Biology
Plant Physiology
Quick fact
Plants can 'hear' themselves being eaten and release chemicals to attract predators of the herbivore.
Why this is interesting
If you've ever wondered how a tiny seed knows to grow upward and when to flower—or how a tree can lift water hundreds of feet—plant physiology holds the answers.
Read the full explanation
Understanding Plant Physiology
Plant physiology is the study of how plants operate. Think of a plant as a chemical factory powered by sunlight. It takes in carbon dioxide from the air and water from the soil to make sugars through photosynthesis. Water travels up from roots through tiny tubes called xylem, thanks to evaporation from leaves. Sugars travel to growing parts through phloem. Plants also sense light, gravity, and touch, using hormones to bend, grow, and flower at the right times. These processes are finely tuned to the environment, allowing plants to survive droughts, seasons, and attacks.
A deeper explanation
At the core of plant physiology are integrated systems. Transpiration pulls water upward due to cohesion and adhesion in xylem vessels, creating negative pressure. Photosynthesis converts light energy into chemical energy, with the Calvin cycle fixing carbon into sugars. Phloem transport is driven by osmotic pressure differences—a pressure flow hypothesis. Plant hormones like auxin control growth direction via asymmetric distribution, causing phototropism (bending toward light). Gibberellins regulate stem elongation and seed germination. Photoperiodism involves detecting day length through phytochrome pigments, enabling flowering in response to seasons. Stomata open and close based on guard cell turgor, balancing gas exchange with water loss. Understanding these mechanisms is critical for improving crop yields, developing drought-resistant plants, and predicting ecosystem responses to climate change.