(a) What do you mean by new generation plant growth regulators? Enlist the different new generation plant growth regulators and…

(a) New Generation Plant Growth Regulators and Abiotic Stress Mitigation

New generation plant growth regulators (PGRs) refer to recently identified, low-molecular-weight signaling molecules that regulate plant development and stress responses, distinct from classical auxins, cytokinins, and gibberellins. Unlike classical PGRs, which primarily drive growth, these newer classes often function as stress-responsive signals. Key examples include brassinosteroids, derived from campesterol; jasmonates, synthesized from linolenic acid; salicylic acid, derived from phenylalanine; strigolactones, originating from carotenoid metabolism; and peptide hormones like systemins.

Their role in mitigating abiotic stresses is profound. Brassinosteroids enhance drought and salinity tolerance by modulating stomatal closure and upregulating antioxidant enzymes, thereby reducing oxidative damage. Jasmonates play a dual role; while primarily associated with herbivory, they also mediate osmotic stress responses by regulating ion homeostasis and root architecture. Salicylic acid is crucial for heat and chilling stress tolerance, acting as a signal for thermotolerance by inducing heat-shock proteins and stabilizing membranes. Strigolactones assist in nutrient deficiency stress, particularly phosphorus and nitrogen, by promoting root hair development and symbiotic associations with mycorrhizae, thus enhancing nutrient uptake under limiting conditions.

(b) Micronutrient Deficiencies and Strategies against Protein-Energy Malnutrition

Micronutrient deficiencies in humans are widespread in India, with significant health implications. Iron-deficiency anemia remains the most prevalent, with NFHS-5 data indicating that 57.0% of women and 67.1% of children aged 6–59 months suffer from anemia. Zinc deficiency impairs immune function and growth, while iodine deficiency disorders lead to cognitive impairment and goiter. Vitamin A deficiency causes night blindness and increased susceptibility to infections. These deficiencies are often interlinked with protein-energy malnutrition (PEM), which stunts physical and cognitive development.

Strategies to combat PEM, with special reference to women and children, are multi-pronged. The Integrated Child Development Services (ICDS) scheme provides supplementary nutrition and health check-ups to children below six and pregnant/lactating women. The Mid-Day Meal Scheme (renamed PM POSHAN in 2021) ensures school children receive at least one hot cooked meal, addressing both hunger and micronutrient gaps. The POSHAN Abhiyaan (National Nutrition Mission) focuses on reducing anemia, stunting, and wasting through convergence of existing programs. Biofortification is another critical strategy, involving the cultivation of nutrient-dense crops like iron-rich pearl millet and zinc-rich wheat to address dietary gaps at the source, alongside Anemia Mukt Bharat (iron–folic acid supplementation) and fortified rice supplied through PDS and PM POSHAN. Supplementary nutrition programs specifically target pregnant and lactating women to prevent intergenerational transmission of malnutrition.

(c) Mycoplasmal Diseases and Physiological Disorders of Potato

Mycoplasmal diseases, now termed phytoplasma diseases, are caused by wall-less bacteria transmitted by insect vectors. In potato, purple top wilt and aster yellows are notable examples, characterized by leaf curling, yellowing, and stunting. These are primarily transmitted by leafhoppers. Witches' broom, another phytoplasma-induced disorder, results in dense clusters of shoots. It is important to distinguish these from psyllid yellows, which is a non-phytoplasma disorder caused by psyllid feeding.

Physiological disorders in potato are non-infectious and often related to environmental or cultural factors. Hollow heart is caused by rapid tuber growth due to excess nitrogen, leading to a hollow cavity in the center. Internal brown spot results from high soil temperature and moisture stress (often with low calcium), causing scattered brown necrotic spots in the tuber flesh. Blackheart is a disorder caused by oxygen deficiency in the tuber (high temperature, poor aeration or waterlogging), leading to blackening of the tuber flesh. Stem-end browning is a vascular discoloration at the stem end of the tuber, associated with heat and moisture stress during tuber growth.