The Role of Plant Hormones in Mediating Crop Responses to Multiple Concurrent Abiotic Stresses in Nigerian Tropical Conditions

This study investigates the role of plant hormone networks in mediating crop responses to multiple concurrent abiotic stresses under Nigerian tropical conditions, contributing an original understanding of the complex phytohormonal regulation of stress tolerance that is relevant to both fundamental plant biology and applied agronomic stress management. Crops in Nigerian field conditions rarely experience single stresses in isolation, but rather encounter combinations of drought, heat, waterlogging, nutrient deficiency, and salt stress simultaneously or in rapid succession. Plant hormone signalling networks, particularly the interactions among ABA, ethylene, jasmonic acid, salicylic acid, and cytokinins, coordinate responses to these multiple stresses, but the dynamics of hormone crosstalk under combined tropical stresses have been inadequately characterised. This study exposes maize, sorghum, and cowpea to factorial combinations of dual and triple abiotic stress treatments including drought-heat, drought-nutrient stress, and drought-heat-nutrient combinations at physiologically representative intensities calibrated to Nigerian field conditions. Hormone profiling using UPLC-MS measures endogenous levels of eight hormones at critical stress time points. Gene expression analysis of key hormone biosynthesis and signalling genes uses quantitative RT-PCR. Phenotypic responses including stomatal closure, antioxidant enzyme activity, yield components, and recovery ability after stress removal are linked to hormone profiles. Findings reveal that concurrent drought-heat stress uniquely activates an ABA-ethylene synergistic response that accelerates leaf senescence, causing 34 percent more yield loss than expected from additive single stresses. Cowpea shows the most robust hormone buffering capacity under triple stress. The study contributes original multiple stress hormone crosstalk data and recommends targeted hormone priming protocols for field stress management.

Keywords: plant hormones, multiple abiotic stresses, phytohormonal crosstalk, Nigeria, stress tolerance.