(a) What is the role and importance of "Seed treatment campaign" in India in the context of quality crop establishment ? 15 (b)…

(a) Role and importance of seed treatment campaigns in quality crop establishment

Seed treatment is the application of fungicides, insecticides, bio-agents or nutrients to seed before sowing, as dressing, coating, pelleting or priming. Seed treatment campaigns, run before kharif and rabi sowing by State Agriculture Departments, Krishi Vigyan Kendras and ICAR institutes, take this practice to farmers.

Role: it protects the seed and seedling from seed-borne and soil-borne pathogens such as Fusarium, Rhizoctonia, smuts and bunts (carbendazim, thiram, carboxin, metalaxyl for downy mildews) and from soil pests such as termites and white grubs (imidacloprid, thiamethoxam). Bio-agents such as Trichoderma and Pseudomonas fluorescens give biological protection, and Rhizobium, Azotobacter and PSB cultures add nitrogen and phosphorus. Bio-priming and nutrient seed treatments, such as zinc, improve emergence and early vigour.

Importance: higher and more uniform germination and plant stand, less replanting, early protection at the critical establishment stage, lower later pesticide use because treatment is cheap and targeted, and more efficient use of certified seed alongside the Seeds Act, 1966 and National Seed Policy, 2002. Treatment protects seed quality but does not replace use of certified seed of improved varieties.

(b) DNA fingerprinting and its applications in modern agriculture

DNA fingerprinting identifies an individual, variety or genotype by its unique pattern of DNA polymorphisms, detected with markers such as RFLP, RAPD, AFLP, microsatellites (SSR) and SNPs. Unlike a transgenic or genetic-engineering method, it only reads existing variation.

Applications: variety identification and protection, as molecular profiles support DUS testing and registration under the PPV&FR Act, 2001 and help resolve disputes over essentially derived varieties; hybrid seed purity testing, replacing slow grow-out tests; detection of adulteration, for example in basmati rice, where DNA tests check for non-basmati admixture; genetic diversity analysis and management of germplasm in gene banks such as the National Gene Bank at NBPGR, including identification of duplicates; breeding, where markers help choose parents and, with marker-assisted selection, trace traits; and testing for GM traits in seed lots and food.

(c) Mechanisms of water absorption in plants and factors affecting the rate

Water is absorbed mainly by root hairs in the zone of maturation, moving across the cortex by the apoplastic route (cell walls and spaces), the symplastic route (through plasmodesmata) and the transmembrane route aided by aquaporins, and then crossing the endodermis, where the Casparian strip forces water through cells, into the xylem. Absorption is passive or active.

Passive absorption is the main mechanism, accounting for most uptake in actively transpiring plants. Transpiration at the leaves creates tension in the xylem, which pulls water up through the cohesion of water molecules, so roots act as passive absorbing surfaces and water moves down a water potential gradient from soil to root.

Active absorption is driven by root metabolism and works when transpiration is low, such as at night, in humid air or in young plants. Active accumulation of solutes in xylem sap lowers its water potential and draws water in, creating root pressure, which causes guttation.

Factors: soil water availability (best near field capacity, falling to nil at permanent wilting point); soil temperature (optimum about 20-30°C; cold reduces viscosity-driven uptake and root metabolism); soil aeration, since oxygen is needed for root respiration and active uptake; concentration of the soil solution, since saline soils lower soil water potential; transpiration rate, raised by light, low humidity and wind; extent of the root system, with its depth, density and root hairs; and mycorrhizal association, which extends the absorbing area.