Hormetic doses of lead metal ion stimulated photosynthetic attributes in Brassica juncea  during various stages of growth

Low doses of lead (Pb) ions were used in the present study to investigate their effects on photosynthetic efficiency in Brassica juncea. Plants of B. juncea grown for 30, 45, and 60 days were analysed for root and shoot length, pigment content, gas exchange, chlorophyll fluorescence, primary and secondary metabolites, and nonenzymatic antioxidant responses under exposure to hormetic doses of Pb2+. The findings show that low levels of Pb2+ (especially 18- and 36-µM Pb treatments) improve gas exchange metrics, chlorophyll fluorescence parameters, root and shoot growth, and increased amounts of chlorophyll, carotenoid, xanthophyll and low amounts of pheophytin as compared with untreated B. juncea plants aged 30, 45, and 60 days. The study also shows increased concentrations of total sugar, free amino acids, anthocyanins, phenolics, flavonoids, and antioxidants (ascorbic acid and tocopherol). T his study emphasises the positive relationship between low Pb doses and plant-stage-dependent morphophysiological and biochemical responses, shedding light on the possible implications of hormesis for improving plant health and resilience across various growth stages.