(a) Define seed viability. Describe in brief the metabolic aspects of seed germination. 10 (b) Define 'Pests' and 'Pesticides'…

(a) Seed viability and metabolic aspects of germination

Seed viability is the capacity of a seed to remain alive and to germinate and produce a normal seedling under favourable conditions, tested by germination, tetrazolium (TTC) staining or embryo excision. Viability differs from vigour, which is the potential for rapid, uniform emergence under field stress.

Metabolic events: first, rapid imbibition rehydrates tissues, repairs membranes and DNA and resumes respiration, at first partly anaerobic and then aerobic through the Krebs cycle and oxidative phosphorylation, supplying ATP. Second, a lag phase of enzyme activation and use of stored mRNA follows. Third, reserves are mobilised: in cereals, gibberellin from the embryo reaches the aleurone layer and induces α-amylase, proteases and lipases that digest starch, protein and lipid into sugars, amino acids and fatty acids; in oilseeds, lipids are converted to sugars through the glyoxylate cycle. Abscisic acid falls as gibberellin rises. The soluble nutrients are carried to the embryonic axis, supporting cell division, elongation and radicle emergence.

(b) Pests, pesticides, and types and need for formulations

A pest is any organism, whether insect, mite, nematode, pathogen, weed or vertebrate, that damages crops or produce and whose population exceeds the economic threshold, causing economic loss. A pesticide is any chemical or biological substance used to prevent, destroy, repel or mitigate pests.

Formulation is the blending of the technical active ingredient with inert carriers, solvents, surfactants and other adjuvants. Types: emulsifiable concentrate (EC), wettable powder (WP), soluble liquid (SL), suspension concentrate (SC), water-dispersible granule (WG), dust (DP), granule (GR), ultra-low-volume liquid (ULV), capsule suspension and baits.

Need: pure active ingredients are highly concentrated, toxic, poorly soluble or unstable, so formulations allow accurate dilution and uniform coverage, stability and shelf life, safer handling, better contact, spread and adhesion on the target, lower phytotoxicity, matching of form to target (granules for soil pests and rice stem borer, dusts for dry application, ULV for low-volume spraying), and cost-effective bio-efficacy.

(c) Post-harvest technology and losses in fruits and vegetables

Fruits and vegetables are perishable because they continue to respire, transpire and ripen after harvest, and are attacked by moulds and bacteria. ICAR-CIPHET studies estimate losses of roughly 5-16% by commodity, which post-harvest technology (PHT) reduces through an integrated chain.

Harvest at the right maturity; pre-cool to remove field heat; clean, sort and grade; cure root and bulb crops such as onion and potato; apply wax or edible coatings that cut moisture loss; pack in ventilated crates and corrugated boxes with modified-atmosphere packaging; store in cold chambers or controlled atmosphere stores that lower respiration and ethylene action; and control ripening in chambers. Irradiation, drying, dehydration, canning, freezing, pulping and juice making convert surplus into shelf-stable products and add value.

Government support includes the Mission for Integrated Development of Horticulture, Pradhan Mantri Kisan SAMPADA Yojana, Operation Greens (2018) and the Agriculture Infrastructure Fund (2020) for cold chain and packhouses.

(d) Plant quarantine and measures in India

Plant quarantine is the legal restriction of movement of plants, planting material, produce and soil to prevent the entry and spread of exotic pests, diseases and weeds into a country or area. In India it is administered by the Directorate of Plant Protection, Quarantine and Storage (DPPQS) under the Destructive Insects and Pests Act, 1914 and the Plant Quarantine (Regulation of Import into India) Order, 2003, with NBPGR as nodal agency for germplasm.

Measures: pest risk analysis; import permits and prohibition of high-risk consignments; phytosanitary certificates from exporting countries; inspection, sampling and testing at ports of entry; fumigation or heat treatment of infested material; post-entry quarantine growing of imported germplasm, as at NBPGR; domestic quarantine of regions, as for potato wart in Darjeeling and Karnal bunt of wheat; and certification of exports, with India following the IPPC and the WTO SPS Agreement. Examples of pests that entered when barriers were weak include Parthenium, with imported wheat, and more recently fall armyworm (2018) and the tomato leaf miner (2014), underlining the need for strong inspection.

(e) Importance of greenhouses in agriculture

A greenhouse is a protected structure, clad with polyethylene film, shade net or glass, in which temperature, humidity, light and carbon dioxide are controlled to give a crop a favourable microclimate. Importance: year-round and off-season production at premium prices; yields several times those of open fields, for crops such as colour capsicum, cucumber and tomato; high-value flowers such as rose, gerbera and carnation; saving of water and fertiliser through drip irrigation and fertigation; protection from rain, frost, heat, hail and many insect pests, so less pesticide is used; production of disease-free nurseries, hardening of tissue-cultured plants and hybrid seed; and cultivation in cold or extreme regions such as Himachal Pradesh and Ladakh. The Mission for Integrated Development of Horticulture subsidises protected cultivation, with significant clusters in Maharashtra, Karnataka, Himachal Pradesh and Punjab.