Plant Physiology
- The oxygenation activity of RuBisCo enzyme in photorespiration leads to the formation of : Answer: 2. 1 molecule of 3-C compound Key idea: In photorespiration RuBisCO acts as an oxygenase on RuBP. RuBP (5C) plus O₂ gives one molecu... 1
- Match the following concerning essential elements and their functions in plants :(a) Iron (i) Photolysis of water(b) Zinc (ii) Pollen germination(c) Boron (iii) Required for chlorophyll biosynthesis(d) Manganese (iv) IAA biosynthesisSelect the correc… Answer: 3. (a) (iii), (b) (iv), (c) (ii), (d) (i) Key idea: Recall the role of each element. Iron: needed for chlorophyll biosynthesis (iii)... 1
- The process responsible for facilitating loss of water in liquid form from the tip of grass blades at night and in early morning is : Answer: 2. Root pressure Key idea: Loss of liquid water from leaf tips at night is guttation, caused by root pressure. At night, with high s... 1
- The process of growth is maximum during : Answer: 1. Log phase Key idea: Growth follows a sigmoid curve and is fastest in the exponential (log) phase. In the lag phase growth is slow... 1
- It takes very long time for pineapple plants to produce flowers. Which combination of hormones can be applied to artificially induce flowering in pineapple plants throughout the year to increase yield ? Answer: 1. Auxin and Ethylene Key idea: Auxin and ethylene induce flowering in pineapple. Auxins (like NAA) and ethylene (ethephon) promote... 1
- Conversion of glucose to glucose-6-phosphate, the first irreversible reaction of glycolysis, is catalyzed by : Answer: 2. Hexokinase Key idea: Hexokinase phosphorylates glucose using ATP to give glucose-6-phosphate, the first irreversible step. Phosph... 1
- What is the direction of movement of sugars in phloem ? Answer: 4. Bi-directional Phloem moves sugars from a source to a sink. The source and sink can be anywhere, so movement can be upward or dow... 1
- What is the site of perception of photoperiod necessary for induction of flowering in plants ? Answer: 4. Leaves Key idea: Photoperiod is sensed by the leaves. Leaves perceive the light/dark duration and produce a flowering stimulus (f... 1
- Respiratory Quotient (RQ) value of tripalmitin is : Answer: 2. 0.7 RQ=volume of CO₂ released/volume of O₂ used . Tripalmitin (a fat) oxidises as mathrm2C₅₁H₉₈O₆ + 145 O₂ → 102 CO₂ + 98 H₂O . R... 1
- Which of these statements is incorrect ? Answer: 4. Oxidative phosphorylation takes place in outer mitochondrial membrane. Key idea: Check where each respiratory step occurs. TCA cy... 1
- Which of the following elements is responsible for maintaining turgor in cells ? Answer: 2. Potassium Potassium regulates osmotic potential, so it maintains turgor and opens stomata. Mg is in chlorophyll, Ca is in the mid... 1
- In which of the following forms is iron absorbed by plants ? Answer: 4. Both ferric and ferrous Plants take up iron mainly as ferric ions (Fe ³⁺ ), and it is also taken as ferrous ions (Fe ²⁺ ). Since... 1
- What is the role of NAD^+ in cellular respiration ? Answer: 3. It functions as an electron carrier. NAD ^+ is a coenzyme that accepts electrons and hydrogen to become NADH, so it is an electro... 1
- Oxygen is *not* produced during photosynthesis by Answer: 1. Green sulphur bacteria Green sulphur bacteria perform anoxygenic photosynthesis using H ₂ S, so they release no oxygen. Cycas (pl... 1
- Stomatal movement is *not* affected by Answer: 2. O ₂ concentration Stomata respond to light, CO ₂ level, temperature and water status, but not to O ₂ concentration. Low CO ₂ and... 1
- Which of the following is *not* a product of light reaction of photosynthesis ? Answer: 3. NADH The light reaction makes ATP and NADPH and releases O ₂ from photolysis of water. NADH is a respiration carrier, not a produ... 1
- Which statement is wrong for Krebs' cycle ? Answer: 3. The cycle starts with condensation of acetyl group (acetyl CoA) with pyruvic acid to yield citric acid The wrong statement is opt... 1
- With reference to factors affecting the rate of photosynthesis, which of the following statements is not correct ? Answer: 2. C₃ plants respond to higher temperatures with enhanced photosynthesis while C₄ plants have much lower temperature optimum The wro... 1
- Fruit and leaf drop at early stages can be prevented by the application of : Answer: 2. Auxins Auxins prevent early fruit and leaf drop (abscission) in plants. Ethylene promotes abscission and ripening, so it does the... 1
- Phosphoenol pyruvate (PEP) is the primary CO_2 acceptor in : Answer: 1. C₄ plants Key idea: The first CO₂ acceptor differs in C3 and C4 plants. In C₄ plants, phosphoenol pyruvate (PEP) in the mesophyll... 1
- The water potential of pure water is : Answer: 4. Zero Key idea: Water potential ( Psi_w ) of pure water at standard conditions is taken as the maximum reference value. It is zero... 1
- Oxidative phosphorylation is Answer: 3. formation of ATP by energy released from electrons removed during substrate oxidation Oxidative phosphorylation is the formation... 1
- Which of the following biomolecules is common to respiration-mediated breakdown of fats, carbohydrates and proteins? Answer: 3. Acetyl CoA Carbohydrates, fats and proteins are all finally oxidised through the Krebs cycle, which they enter as acetyl CoA. Pyr... 1
- The process which makes major difference between C_3 and C_4 plants is Answer: 2. photorespiration The big difference is photorespiration. In C₃ plants RuBisCO also acts as an oxygenase, causing a loss of fixed... 1