(a) Define water stress. Discuss the effects of water stress on anatomical and physiological changes in plant growth. Also…

(a) Water Stress: Anatomical, Physiological Changes, and Indicators

Water stress occurs when plant transpiration exceeds root water absorption, causing internal plant water deficit; this physiological state differs from meteorological drought, which is a prolonged atmospheric precipitation deficiency. In a wider sense water stress also includes excess water (waterlogging, which causes oxygen deficiency in roots), but the term usually refers to deficit.

Anatomically, water stress restricts cell turgor, causing reduced cell elongation and leaf expansion, reduction in xylem vessel diameter to prevent cavitation, an increased root-shoot ratio as roots proliferate deeper, leaf rolling to reduce surface exposure, a thicker cuticle and wax layer, smaller and more compact cells, and greater lignification and sclerenchyma (xeromorphic features). Physiologically, it induces rapid Abscisic Acid (ABA) accumulation, precipitating stomatal closure, reduced carbon dioxide assimilation, impaired photosynthesis, and loss of membrane integrity. Plants counter this via osmotic adjustment, accumulating compatible solutes like proline and soluble sugars.

Plant water stress indicators are classified into: Soil-based indicators: soil moisture content and the per cent depletion of available soil moisture between field capacity and permanent wilting point (irrigation commonly at about 50% depletion), and soil water potential measured with tensiometers or resistance blocks (e.g., irrigating wheat at about −0.5 bar at 15 cm depth). Weather-based indicators: the IW/CPE ratio based on cumulative USWB Class A pan evaporation, reference evapotranspiration (ET₀, e.g., FAO Penman–Monteith) and crop ET deficit from a climatic water balance, and aridity or moisture indices. Plant-based indicators (for completeness): leaf water potential, relative water content, stomatal conductance, and canopy-to-air temperature difference measured by infrared thermometry, from which the Crop Water Stress Index (CWSI) is calculated using the vapour pressure deficit.

(b) Rice Tungro Disease: Etiology, Symptoms, and Management

Rice tungro disease is caused by an obligate viral complex: Rice Tungro Bacilliform Virus (RTBV, a double-stranded DNA virus causing symptom severity) and Rice Tungro Spherical Virus (RTSV, a single-stranded RNA virus required for vector transmission). The complex is transmitted semi-persistently by green leafhoppers, mainly Nephotettix virescens (also N. nigropictus); the virus is not seed-borne.

Prevalent in endemic tracts of Tamil Nadu, Andhra Pradesh, and West Bengal, characteristic symptoms include marked plant stunting, leaf discoloration turning yellow-to-orange beginning from the tips, reduced tillering, delayed flowering, and sterile, discolored panicles.

Management relies on an integrated approach: Host-plant resistance: Deploying tungro- or vector-resistant cultivars such as Vikramarya, IR36 and IR64 (vector resistance can break down as leafhopper populations adapt). Vector control: Nursery and field application of systemic insecticides like imidacloprid or thiamethoxam. Cultural practices: Synchronous planting across contiguous tracts, destruction of weed hosts, and roguing of early infected hills. Nutrient management: Applying balanced NPK fertilization while avoiding excessive basal nitrogen.

(c) Food Inflation: Drivers and Mitigation Strategies

Recent food inflation episodes (2022–2024, led by vegetables, pulses and cereals) highlight dual pressures: Demand-side drivers: Sustained economic growth leading to rising disposable incomes, urbanization, and structural dietary diversification toward high-value proteins, fruits, and dairy. Supply-side drivers: Extreme weather shocks (heatwaves affecting wheat, unseasonal rains hitting horticulture), rising input costs (fertilizer, diesel), supply-chain bottlenecks, and upward revisions in Minimum Support Prices (MSP).

Mitigation requires coordinated interventions: open market sale of wheat and rice from FCI buffer stocks (OMSS); buffers of pulses and onion under the Price Stabilisation Fund (merged into PM-AASHA in 2024) and retail sale of 'Bharat' atta, dal and rice; dynamic export-import calibrations (for example, the curbs on non-basmati rice exports in 2023, later relaxed, and duty-free pulse imports); stock limits on traders; investment in cold storage and food processing to cut perishables' price spikes; pan-India market integration via e-NAM; and protecting vulnerable populations through the Targeted Public Distribution System (TPDS).