Plant Stress Biology — DU B.Sc. (Hons.) Botany Previous Year Question Papers

PLANT STRESS BIOLOGY 3. All parts of questions must be attempted together. 5. Draw well labelled diagrams wherever necessary. Q1. (a) Fill in the blanks (any five): I. iii. 5 x 1= 5 marks Soil containing high Na2C03 and.high sodium absorption ratio due to low [Mgj+I and [Cat| known as ............... The process by which plants accumulate low-molecular-weight organic compounds to maintain osmotic balance under stress is called is a compatible solute synthesized from glutamate and is particularly accumulated under drought and salinity stress. iv. Under drought stress, stomatal closure is primarily mediated by the phytohormone V. are low-molecular-weight proteins induced by pathogen attack that include chitinases, glucanases, and thaumatin-like proteins. vi. The protection of a host against a wide range of pathogens is known as the resistance. (b) Expand the following (any five): 5 x 1= 5 marks i. POD ii. PUFA iii. SOS iv. HR V. PR proteins vi. CDPK (c) Define the following (any five): 5 × 1= 5 marks i. Phenotypic plasticity ii. Phytoalexins ili. Osmolytes iv. Aquaporins v. Herbivory vi. Allelopathy Q2. Differentiate between the following (any three): i. Abiotic and biotic stress ii. Pattern-triggered immunity and effector-triggered immunity iii. LEA proteins and HSPs iv. Mutation breeding and protected cultivation Q3. Write short notes (any three): i. Ion homeostasis ii. Systemic acquired resistance (SAR) iii. Role of NO in stress signalling iv. Stress-tolerant genetically engineered plants Q4.(a)Discussthephysiologicalandbiochemicalresponsesofplantstodroughtstres;.8marks (b) What are antioxidant engymes? Discuss their role in plant stress tolerance. 7 marks Q5. (a) What are reactive oxygen species QOS)? Explain their role in plant stress biology. (b) What are secondary metabolites? Discuss the role of any one class of secondary metabolites in tolerance against environmental stress. 8 marks Q6. (a) Discuss in detail the role of Abscisic Acid (ABA) in stomatal regulation and how it mediates drought tolerance. 8 marks (b) What are calcium-binding proteins? Explain calcium-mediated stress signalling 7 marks responses in plants?