Agromorphological responses and metabolite localization in mungbean (Vigna radiata (L.) R. Wilczek) varieties subjected to drought stress during vegetative and reproductive stages

This research investigated the effect of drought stress on agromorphorlogical responses and metabolite distribution. The first study focused on the agromorphological responses of four mungbean varieties to drought stress at different growth stages. It showed significant variations in days to maturity, plant height, leaf area, leaf dry weight, stem dry weight, root dry weight root-shoot ratio, and harvest index. Pag-asa 5 and Pag-asa 15 were identified as early-maturing varieties. Leaf area reduction was noted under drought, particularly in Pag-asa 5 and Pag-asa 7 during the reproductive stage. Despite reduced leaf dry weight and root development, Pag-asa 5 displayed the highest harvest index and the heaviest 100-seed weight, while Pag-asa 15 exhibited higher pod counts. Correlation analysis revealed associations between days to maturity and pods per plant and positive correlations between plant height, pods per plant, root dry weight, and yield. The second study assessed the root architectural traits in response to drought stress. Root architectural traits were mostly stable across varieties, except for Pag-asa 5, which showed reduced hypocotyl root length under drought condition. The third study used histochemical techniques to examine the anatomical structure and distribution of critical metabolites in two mungbean varieties, Pag-asa 5 and Pag-asa 15. Pag-asa 5 showed distinct brown coloration, wider piths, and structural adaptations to water scarcity in leaves, stems, and roots. In contrast, Pag-asa 15 showed consistent brown coloration and prominent rays in vascular tissue. Starch accumulation was widespread in vascular tissues and parenchymatous cells, while lipid distribution increased under drought stress in Pag-asa 5. Phenolic compounds and tannins are relatively high in Pag-asa 15. Further field studies should be pursued to validate these findings and explore coping mechanisms, particularly focusing on root architecture and metabolite localization under drought stress in mungbean varieties.