Biotic stressors, such as pathogens and herbivorous insects, significantly reduce global agricultural productivity, resulting in estimated annual yield losses of 10–40% and considerable economic damage. Plant nutritional status fundamentally influences defense mechanisms against these biotic challenges. This comprehensive review examines the multifaceted roles of mineral nutrients in enhancing plant immune responses and resilience to biotic stress factors. This review examines how macronutrients (N, P, K, Ca, Mg, S) and micronutrients (Fe, Zn, Mn, Cu, B, Cl, Si) influence plant defense through strengthening structures, regulating biochemical pathways, and activating signalling cascades. It specifically highlights the dual roles of nitrogen in forming structural barriers and influencing pathogen susceptibility, potassium’s role in regulating stomatal function and activating defense enzymes, calcium’s contribution in maintaining cell wall integrity and defense signalling, as well as the catalytic functions of micronutrients in antioxidant systems and phenolic compound synthesis. The review also explores mechanistic aspects of nutrient-mediated immunity, including calcium-dependent signalling pathways, potassium-regulated jasmonic acid synthesis, nitrogen modulation of defense-related proteins, and micronutrient cofactor roles in reactive oxygen species metabolism. Furthermore, the review examines nutrient combinations that work synergistically to improve effectiveness against certain pathogens and pests, while also assessing practical applications of strategic nutrient management in various cropping systems. It concludes by highlighting existing knowledge gaps and suggesting future research avenues, with a focus on integrating molecular methods to clarify nutrient-defense interactions and validating nutrient-based strategies in various agroecological regions.

Melatonin (MT), a naturally occurring compound, is found in various species worldwide. In 1958, it was first identified in the pineal gland of dairy cows. MT is an “old friend” but a “new compound” for plant biology. It brings experts and research minds from the broad field of plant sciences due to its considerable influence on plant systems. The MT production process in plants and animals is distinct, where it has been expressed explicitly in chloroplasts and mitochondria in plants. Tryptophan acts as the precursor for the formation of phyto-melatonin, along with intermediates including tryptamine, serotonin, N-acetyl serotonin, and 5-methoxy tryptamine. It plays a vital role in growth phases such as the seed germination and seedling growth of crop plants. MT significantly impacts the gas exchange, thereby improving physio-chemical functions in plant systems. During stress, the excessive generation and accumulation of reactive oxygen species (ROS) causes protein oxidation, lipid peroxidation, nucleic acid damage, and enzyme inhibition. Because it directly acts as an antioxidant compound, it awakens the plant antioxidant defense system during stress and reduces the production of ROS, which results in decreasing cellular oxidative damage. MT can enhance plant growth and development in response to various abiotic stresses such as drought, salinity, high temperature, flooding, and heavy metals by regulating the antioxidant mechanism of plants. However, these reactions differ significantly from crop to crop and are based on the level and kind of stress. The role of MT in the physiological functions of plants towards plant growth and development, tolerance towards various abiotic stresses, and approaches for enhancing the endogenous MT in plant systems are broadly reviewed and it is suggested that MT is a steering compound in directing major physiological functions of plants under the changing climate in future.

The foliar application of nutrients and plant growth regulators (PGRs) at critical crop growth periods can improve the yield of field crops. Hence, the present study was conducted to quantify the effects of the combined application of nutrients and PGRs (crop-specific formulation) on maize, blackgram, greengram, groundnut, cotton, sugarcane, and coconut yield. In all the crops except coconut, the treatments included (i) a foliar spray of crop-specific nutrients and PGR combinations and (ii) an unsprayed control. In coconut, the treatments included (i) the root feeding of coconut-specific nutrients and PGR combinations and (ii) an untreated control. Crop-specific nutrient and PGR formulations were sprayed, namely, Tamil Nadu Agricultural University (TNAU) maize maxim 1.5% at the tassel initiation and grain-filling stages of maize, TNAU pulse wonder 1.0% at the peak flowering stage of green gram and black gram, TNAU groundnut-rich 1.0% at the flowering and pod-filling stages of groundnut, TNAU cotton plus 1.25% at the flowering and boll development stages of cotton, and TNAU sugarcane booster 0.5% at 45 days after planting (DAP), 0.75% at 60 DAP, and 1.0% at 75 DAP of sugarcane. The results showed that the foliar application of TNAU maize maxim, TNAU pulse wonder, TNAU groundnut-rich, TNAU cotton plus and TNAU sugarcane booster and the root feeding of TNAU coconut tonic increased the yield of maize, pulses, groundnut, cotton, sugarcane, and coconut, resulting in higher economic returns.

Background: Foxtail millet is one of the nutri-cereal foods for the people of semi arid regions. Proper nutrient management and source-sink alteration are major keys for achieving higher productivity in millets. However, potassium is not recommended to foxtail millet and the potential yield is not exploited. And also the study of source-sink alteration in foxtail millet by using plant growth regulators is meager. Methods: An experiment was conducted to study the impact of plant growth retardants viz., chlormequat chloride (CCC) and mepiquat chloride (MC) with the nutrient potassium (K2SO4 - 1%) on growth, gas exchange parameters and grain yield of foxtail millet under rainfed condition. Plant growth retardants with potassium consortium were used as foliar spray at flower initiation stage under field condition. Standard methods were used to measure the plant height, root length, number of leaves, LAD, CGR and grain yield. The photosynthetic rate, transpiration rate and leaf temperature were measured by using the instrument PPS. Result: Foliar spray of CCC (250 ppm) with 1% K2SO4 showed supremacy to enhance crop growth rate, leaf area duration, photosynthetic rate, transpiration rate and grain yield compared to other treatments. However, lowest plant height (100.7 cm) and number of leaves were observed by CCC (250 ppm) alone. Highest photosynthetic rate (26.84) and transpiration rate (17.94) were registered by CCC + K2SO4. Lowest leaf temperature of 34.1ºC was registered by 1% K2SO4 compared to control (35.6°C). CCC with K2SO4 recorded highest LAD value of 46.1 which is on par with K2SO4 alone (45.9). CCC with K2SO4 registered highest grain yield of 2.13 t ha-1 with increased yield of 18.3% over control. However, highest benefit cost ratio of ratio of 2.75 was recorded by 1% K2SO4 alone.

Background: Photosensitivity in horsegram restricts horizontal expansion in its cultivable area. Using induced mutagenesis, photo-insensitive mutants of a popular variety PAIYUR 2 were evolved. Methods: The mutants were experimented with across seasons and locations. All the experiments were conducted in the randomized block design with five replications. The AMMI and GGE biplot models were employed to tag the best-yielding and stable genotype(s). Result: The ANOVA indicated significant effects of genotypes (G), environments (E) and their combined genotype × environment interaction (G × E) for all the experimental traits implying a large range of variation. The interaction effect in AMMI has been partitioned into several principal components. Of the six Principal Components (PC), the first PC explained the major variation. It is 60.20% for the number of clusters per plant, 99.60% for days to fifty percent flowering, 92.57% for the number of pods per cluster, 96.63% for the number of pods per plant, 99.66% for days to maturity and 96.34% for yield per hectare. AMMI and GGE biplot analyses helped to identify the best performing and stable photo-insensitive mutants TNAU-HG-DM-001 and TNAU-HG-DM-004 for further exploitation.