Root plasticity and ABA regulation under heat in Vigna aconitifolia

Enhancing the resilience of underutilized legumes to abiotic stress is essential for food security in arid and semi-arid regions. Vigna aconitifolia (moth bean) is a heat- and drought-tolerant crop with potential for climate-resilient agriculture; however, its root adaptive mechanisms remain poorly understood. In this study, two contrasting genotypes, TN67 (wild) and IPCmo056 (cultivated), were exposed to heat stress (40°C) and exogenous abscisic acid (ABA; 10, 25, and 50 µM) for six days to evaluate morphological and cellular responses. Root system architecture was quantified through digital imaging, and cell length profiles were used to assess meristem organization. Under heat stress, TN67 maintained primary root elongation and lateral branching, whereas IPCmo056 showed reduced root volume and compensatory basal root proliferation. Moderate ABA (10 µM) enhanced lateral root initiation in TN67, while IPCmo056 exhibited a biphasic response with inhibition at higher concentrations, indicating greater hormonal sensitivity. Quantitative plasticity indices confirmed superior adaptive capacity in TN67. Overall, TN67 preserved root growth and meristem structure under combined heat and ABA stress, highlighting the central role of ABA-mediated regulation in the species’ stress resilience. These findings provide new physiological insights and support root-based selection strategies for breeding climate-resilient legumes suitable for dry environments.