Growth, photosynthesis and oxidative responses of Solanum melongena L. seedlings to cadmium stress: Mechanism of toxicity amelioration by kinetin

• Cadmium declined photosynthesis and thus growth of eggplant seedlings.
• This was due to enhanced oxidative stress.
• On the contrary, addition of KN (10 μM) together with Cd ameliorated Cd toxicity.
• Thus the application of KN may be considered as one of the strategies to ameliorate Cd toxicity in crops particularly vegetables.

The sand culture experiments were conducted to investigate whether the foliar application of kinetin (KN), a kind of cytokinins alleviates cadmium (Cd) toxicity in Solanum melongena L. seedlings. The Cd1 (3 mg Cd kg−1 soil) and Cd2 (9 mg Cd kg−1 soil) doses of Cd declined growth of S. melongena seedlings in concentration dependent manner which was due to accumulation of Cd in roots and shoots. Kinetin at 10 μM alleviated Cd toxicity which was accompanied by appreciable decrease in Cd accumulation in seedlings. The photosynthetic pigments: Chlorophyll (Chl) a, b and carotenoids (Car) contents, and chlorophyll fluorescence parameters: Fm/F0, Fv/F0 (except Fv/Fm and qP) were decreased while NPQ was raised by Cd, however, with exogenous KN application the damaging effects on photosynthetic pigments and fluorescence parameters were significantly ameliorated. The oxidative stress markers such as superoxide radical, hydrogen peroxide and malondialdehyde (lipid peroxidation) contents were enhanced by both the doses of Cd; however, together with KN these oxidative indices were diminished significantly. Cadmium treatment increased antioxidative enzymes: superoxide dismutase, peroxidase, catalase and glutathione-S-transferase activity and the contents of non-enzymatic antioxidants: non protein thiol and proline as compared to control, and KN application further enhanced the antioxidant capacity in Cd treated and even untreated seedlings. The overall results suggest that foliar application of KN improved the growth performance of S. melongena seedlings even in presence of toxic level of Cd by strengthening the antioxidant system and photosynthetic capacity.