Phytoremediation Potential of Cucumber (Cucumis sativus L.) For Barium (Ba) Uptake Under a Hydroponic System
Abstract
This research examined how Cucumber (Cucumis sativus L.) responds physiologically, biochemically, and through phytoremediation to barium (Ba) stress in a controlled hydroponic environment. Various metrics were assessed, including seed germination rates, growth factors like root and shoot height, levels of photosynthetic pigments, phytohormones, markers of oxidative stress, antioxidant defenses, and metal accumulation at concentrations of 0 (control), 100, 200, and 300 ppm Ba, using a fully randomized design. The presence of barium significantly reduced the seed germination rate, germination energy, and vigor index by 28.57–60.78%, 30.00–79.00%, and 86.67–88.10%, respectively, compared to the control group. At 300 ppm Ba, both shoot and root lengths decreased by more than 60%, alongside a reduction of over 65% in fresh and dry biomass. The levels of chlorophyll a, chlorophyll b, carotenoids, and SPAD values were markedly lower, with chlorophyll a decreasing by as much as 5.08 times at 300 ppm Ba. Additionally, the concentrations of auxin (IAA) and gibberellic acid dropped by 1.59–3.83-fold and 1.87–3.38-fold, respectively. Ba caused oxidative stress, raising malondialdehyde and hydrogen peroxide levels by up to 75.75% and 39.07%, respectively, while the activities of antioxidant enzymes (SOD, CAT, APX) significantly increased, with SOD activity surging over 24 times at 300 ppm. The bioaccumulation study indicated higher Ba retention in the roots (BAF > 1) but low translocation factors (< 0.5), suggesting a potential for phytostabilization.