Putrescine enhances heat stress tolerance in Brassica juncea L. Seedlings by modulating growth and physiological responses

Heat stress resulting from the increasing global temperatures is emerging as a primary constraint on crop productivity and negatively affects plants. Polyamines (PAs), small, positively charged nitrogenous compounds, play essential roles in plant growth, development, and stress responses. Putrescine (Put) functions as a vital growth regulator, promoting both plant growth and resistance to stress. The primary objective of the present research was to explore the mechanisms through which Put (1 mM) mitigates the adverse effects of heat stress on genotypes RH-1707, RH-1708 (thermosensitive) and RH1566 and RH-1999-42 (thermotolerant). Heat stress led to reduction in growth attributes such as shoot length, root length, fresh weight, dry weight, germination percentage, chlorophyll content and relative water content (RWC) whereas it increased membrane damage as was seen by a rise in electrolyte leakage and lipid peroxidation. The application of Put helped alleviate the adverse effects of heat stress by reducing lipid peroxidation and electrolyte leakage whereas boosting chlorophyll content, RWC and growth parameters. Most significant role of Put in reducing the detrimental effects of heat stress was observed in RH-1707 and RH-1708, which were more susceptible to cellular damage under heat stress. This study specifies that Put foliar spray (1mM) is effective in mitigating the effects of heat stress in Brassica juncea L.