Questions
7 questions per NEET paper
Difficulty
Medium-Hard
Importance
High-yield for NEET and CUET Biology sections
Overview
Plant Physiology is the study of internal processes that allow plants to grow, develop, and reproduce, forming the backbone of botanical questions in competitive exams. Mastering the metabolic pathways like photosynthesis and respiration is essential for scoring in NEET and CUET, as these topics test both conceptual clarity and factual memorization.
Photosynthesis
Photosynthesis is the conversion of light energy into chemical energy, occurring in the chloroplasts through light-dependent and light-independent reactions. Aspirants must focus on the Z-scheme, C3 vs C4 pathways, and the rate-limiting factors governed by Blackman’s Law.
- Light reaction occurs in thylakoids; Dark reaction (Calvin cycle) in stroma.
- C4 plants exhibit Kranz anatomy and lack photorespiration.
- Photorespiration is a wasteful process occurring in C3 plants involving RuBisCO.
- Non-cyclic photophosphorylation produces both ATP and NADPH.
- Action spectrum of photosynthesis was first described by T.W. Engelmann.
Respiration
Cellular respiration breaks down glucose to release energy in the form of ATP through Glycolysis, the Krebs cycle, and the Electron Transport Chain (ETC). Exam questions frequently target the site of these reactions and the net yield of ATP in aerobic versus anaerobic conditions.
- Glycolysis (EMP pathway) occurs in the cytoplasm and is common to both aerobic and anaerobic respiration.
- Krebs cycle occurs in the mitochondrial matrix; produces 2 GTP, 6 NADH, and 2 FADH2 per glucose.
- ETC located in the inner mitochondrial membrane uses chemiosmotic coupling.
- Net gain of 36 or 38 ATP per glucose molecule.
- Respiratory Quotient (RQ) = Volume of CO2 evolved / Volume of O2 consumed.
Transport and Mineral Nutrition
This subtopic explores how plants move water, minerals, and food through xylem and phloem, alongside the essential roles of macro and micronutrients. Key concepts involve the pressure-flow hypothesis and the active uptake of ions against concentration gradients.
- Transpiration pull is the primary driver of water ascent in xylem.
- Mass flow hypothesis explains translocation of sugars from source to sink.
- Essential elements are categorized based on quantitative requirements (Macro vs Micro).
- Nitrogen fixation involves the enzyme Nitrogenase which is highly sensitive to O2.
- Deficiency symptoms manifest first in young or old tissues based on element mobility.
Plant Growth Regulators (PGRs)
PGRs are chemical substances that regulate growth and development, acting as promoters or inhibitors. Memorizing the physiological effects and the specific plant discovery stories for Auxins, Gibberellins, Cytokinins, Ethylene, and ABA is a high-yield exam strategy.
- Auxin (IAA): Responsible for apical dominance and phototropism.
- Gibberellin (GA3): Used to increase internode length and break seed dormancy.
- Cytokinins: Promote cell division and delay senescence (Richmond-Lang effect).
- Ethylene: Gaseous hormone that promotes fruit ripening.
- Abscisic Acid (ABA): Stress hormone that induces stomatal closure.
Exam Tip
Focus heavily on the stoichiometry of the Calvin cycle and the specific enzymatic sites of the Krebs cycle, as these are the most common spots for numerical and 'match the column' questions.
Common Mistakes
- Confusing the ATP/NADPH yield between cyclic and non-cyclic photophosphorylation.
- Miscalculating the RQ value for different substrates like organic acids vs carbohydrates.
- Assuming photorespiration occurs in C4 plants, which evolved specifically to avoid it.
More Revision Notes
Ready to test yourself?
Play topic-wise Plant Physiology questions in Aspirant Arcade — gamified MCQ practice.
Download Free