(a) Give a detailed account of sucrose metabolism in plants. (b) Enlist and explain the symptoms of plant diseases which disrupt…

(a) Sucrose Metabolism Sucrose metabolism in plants involves its synthesis, transport, and degradation. Synthesis occurs in the cytosol of source tissues, primarily via the sucrose phosphate synthase (SPS) pathway, where UDP-glucose and fructose-6-phosphate combine to form sucrose-6-phosphate, which is then dephosphorylated by sucrose-6-phosphate phosphatase to yield sucrose. This sugar is loaded into the phloem for long-distance transport to sink tissues. In sinks, sucrose is cleaved by invertase (hydrolyzing it into glucose and fructose) or sucrose synthase (converting it to UDP-glucose and fructose). These products fuel respiration, growth, and storage. The balance between SPS and invertase activities regulates the source-sink dynamics, ensuring efficient carbohydrate distribution for plant development.

(b) Photosynthesis-Disrupting Diseases Plant diseases disrupt photosynthesis by physically or chemically impairing leaf function. Leaf spots and blights, caused by fungi like Cercospora or bacteria like Xanthomonas, destroy mesophyll tissue, reducing the effective photosynthetic surface area. Mosaic viruses, such as Tobacco Mosaic Virus, induce chlorosis and necrosis by destroying chlorophyll and disrupting chloroplast ultrastructure, thereby lowering light capture efficiency. Rusts, characterized by uredinia (spore-producing structures), and powdery mildews, which produce superficial mycelia on leaf surfaces, obstruct light penetration and can interfere with gas exchange. Bacterial pathogens like Pseudomonas syringae produce toxins; for instance, phaseolotoxin inhibits ornithine carbamoyltransferase, while coronatine mimics jasmonic acid to promote stomatal opening and chlorosis, indirectly affecting photosynthetic efficiency by altering water status and nutrient flow.

(c) Pesticide Formulations Pesticide formulations are preparations that combine the active ingredient with inert carriers, adjuvants, and solvents to enhance stability, ease of application, and efficacy. They are not necessarily homogeneous; many are heterogeneous mixtures. Key types include Emulsifiable Concentrates (EC), where the active ingredient is dissolved in an organic solvent and emulsified with water; Wettable Powders (WP), which are dry powders that form suspensions in water; Suspension Concentrates (SC), stable liquid suspensions that reduce solvent use; Granules (GR), solid particles for soil application; and Ultra-Low Volume (ULV) formulations, designed for aerial spraying with minimal water. The choice of formulation depends on the target pest, crop sensitivity, and application method, ensuring optimal coverage and minimal environmental impact.

(d) NFSA and PDS Features The National Food Security Act, 2013, mandates the Public Distribution System (PDS) to provide legal entitlement to foodgrains. It covers 75% of the rural and 50% of the urban population. Households are categorized into Priority Households, entitled to 5 kg per person per month, and Antyodaya Anna Yojana (AAY) households, the poorest, entitled to 35 kg per household per month. The Act fixed issue prices of ₹3, ₹2 and ₹1 per kg for rice, wheat and coarse cereals; since 1 January 2023 these entitlements are given free under PMGKAY, extended for five years from January 2024. The Act emphasizes women-headed households by making the eldest woman the primary cardholder, empowering her in ration management. It also establishes a grievance redressal mechanism at district and state levels (District Grievance Redressal Officers and State Food Commissions) to ensure accountability and timely delivery of entitled foodgrains, thereby strengthening food security.

(e) Poverty Alleviation Efforts The Government of India has implemented multi-pronged strategies to alleviate poverty. MGNREGA (now succeeded by the VB-G RAM G Act, 2025) guaranteed 100 days of wage employment per year to rural households, providing a safety net and generating rural infrastructure. PM-KISAN provides direct income support of ₹6,000 annually to all landholding farmer families (initially only small and marginal farmers), boosting their purchasing power. The National Social Assistance Programme (NSAP) offers pensions to the elderly, widows, and disabled, ensuring social security for vulnerable groups. Ayushman Bharat provides health insurance coverage of ₹5 lakh per family per year, preventing catastrophic health expenditures that push families into poverty. Additionally, the Skill India Mission, which includes the Pradhan Mantri Kaushal Vikas Yojana (PMKVY), enhances employability by providing skill training, thereby increasing income generation opportunities for the poor.