What is Plant Physiology?
Plant physiology is the study of how plants function — how they capture light energy, transport water and nutrients, and regulate growth using hormones. It connects processes like photosynthesis, respiration, and transpiration into a single living system. Understanding it explains everything from why plants wilt to how they bend toward light.
Plant physiology is the branch of biology studying the internal functions of plants, including photosynthesis, respiration, water transport (transpiration), and hormone-regulated growth and development.
- 1↓PhotosynthesisChloroplasts convert light energy, CO2, and water into glucose and oxygen.
- 2↓Cellular respirationMitochondria break down glucose to release ATP for cell activities.
- 3↓TranspirationWater evaporates from leaf stomata, pulling more water up from the roots (cohesion-tension).
- 4↓TranslocationPhloem transports sugars from source leaves to growing tissues and storage organs.
- 5Hormonal regulationAuxin, gibberellin, cytokinin, ethylene, and ABA coordinate growth, flowering, and stress responses.
Step-by-step worked examples
A houseplant left in a dark room for two weeks turns pale and stops growing. Explain why.
Without light, chloroplasts cannot carry out photosynthesis Glucose production stops, so the plant lacks energy (ATP) and building blocks for growth Chlorophyll production also decreases without light, causing paleness (chlorosis) Growth halts because there's no sugar for respiration or new cell production
On a hot, dry day, a plant's leaves wilt even though the soil still has some water. Why?
High temperature increases the rate of transpiration through stomata Water loss from leaves exceeds the rate roots can absorb and transport water Cells lose turgor pressure (become flaccid) without enough water The plant wilts to reduce further water loss until conditions improve
A gardener applies a rooting hormone to a plant cutting to encourage new roots. What hormone is likely used and how does it work?
Auxin is the plant hormone that stimulates root initiation and cell elongation Applying auxin to the cut end increases local auxin concentration This triggers cell division and differentiation into new root cells Within days, adventitious roots begin to form at the cut site
Flashcards
Quick quiz
Q1.Which organelle carries out photosynthesis?
Q2.What tissue transports water and minerals upward in a plant?
Q3.Which process causes water loss through leaf stomata?
Q4.Which hormone is primarily responsible for fruit ripening?
The full card deck, worked steps and AI-tutor support for “What is Plant Physiology?” are in Notek — study by hand before your exam.
Common mistakes
Thinking plants only 'breathe' during the day. — Correct: Plants respire (cellular respiration) 24/7; photosynthesis only happens with light.
Confusing xylem and phloem direction. — Correct: Xylem moves water upward (roots→leaves); phloem moves sugars both ways, from source to sink.
Believing transpiration is just water loss with no benefit. — Correct: Transpiration pulls water and minerals up the plant and cools the leaves — it's essential, not wasteful.
Assuming one hormone controls all plant growth. — Correct: Multiple hormones (auxin, gibberellin, cytokinin, ethylene, ABA) interact to regulate different aspects of growth.
FAQ
What is plant physiology?
It's the study of how plants function internally, covering photosynthesis, respiration, water and nutrient transport, and hormone-regulated growth.
What is the formula for plant physiology processes?
There's no single formula, but the overall photosynthesis equation is 6CO2 + 6H2O + light → C6H12O6 + 6O2, a key process studied in plant physiology.
What are examples of plant physiology in action?
A wilting plant on a hot day, a seedling bending toward light, and fruit ripening due to ethylene gas are all plant physiology examples.
How do you study plant physiology effectively?
Break it into core processes — photosynthesis, respiration, transpiration, translocation, and hormone regulation — and connect each to a real-world example.