Physiological, Biochemical and Morphological Responses of Tomato Plants to lead Exposure

IntroductionH eavy metals contaminated soil causes serious issues to crop yield and food safety across the globe.Among the heavy metals lead (Pb) is considered as most persistent and non-essential element, which is continuously entering in agroecosystem through human activities like mining, industrial discharge and massive use of contaminated irrigation water or agrochemicals (Ramadan et al., 2025).As plants uptake Abstract | lead (Pb) toxicity can cause damage to tomato seedlings growth and development which leads to serious threats to food safety and crop productivity on sustainable basis.Lead is considered most persistent, its continuous addition into existing agroecosystem is alarming for human health.Present experiment was aimed to assess the effects of lead on morphology, physiological and biochemical attributes of the tomato seedlings at various concentrations (0, 50, 100, 150, and 200 mg kg -¹ soil) of lead (Pb) grown under controlled greenhouse conditions.From the results it was clearly observed that gradual reduction morphological parameters like plant height, stem diameter, leaf number, shoot biomass and root length was observed with the increase in lead (Pb) concentration, which indicates a dose dependent inhibition of vegetative growth.Physiological analyses revealed significant reductions in chlorophyll a, chlorophyll b, total chlorophyll, total soluble protein, relative water content, stomatal conductance, and photosynthetic rate at higher Pb concentrations, reflecting impaired photosynthetic capacity and water relations.Biochemical analysis depicted that elevated malondialdehyde (MDA) levels, indicating oxidative stress, along with increased proline accumulation and increase in antioxidant enzyme activities (superoxide dismutase, catalase, peroxidase), suggesting activation of defense mechanisms against lead (Pb) induced oxidative stress.Concludingly, these results indicate that lead (Pb) toxicity significantly compromises growth, photosynthetic activity and cellular membrane integrity in tomato plants, while inducing protective biochemical responses.The findings provide deep insight into lead (Pb) toxicity thresholds and the physiological and biochemical strategies adopted by tomato seedlings to mitigate heavy metal stress, with implications for sustainable cultivation in contaminated soils.