Cadmium-induced Perturbations in Growth, Oxidative Defense System, Catalase Gene Expression and Fruit Quality in Tomato

Cadmium (Cd) toxicity causes leaf chlorosis, growth inhibition, and disruption of photosynthetic machinery. A pot experiment was conducted to evaluate the changes in growth, physiochemical attributes and expression level of the catalase (Cat2) gene in two tomato cultivars (cv. Nagina; cv. Roma) under cadmium (Cd) stress. Plants were subjected to various concentrations of Cd in soil medium (0, 160, 320, 640 and 1280 mu M Cd) in full strength Hoagland nutrient solution. Elevated Cd concentrations caused an apparent turn down in plant growth, photosynthetic pigments, and activity of CAT and increased the level of ascorbic acid, proline, H2O2 and malondialdehyde (MDA) and ascorbate peroxidase (APX) peroxidase (POD) activities. The fruit biomass, moisture content, total fiber, protein, glucose and fructose contents were decreased. In addition, Cd induced alterations in some nutrient elements; for instance, Ca2+ decreased and K+ in fruit was increased in response to Cd toxicity. Cadmium contents in fruit decreased evidently under elevated levels of Cd. The results of the present study demonstrated that Cd toxicity severely deteriorated the fruit quality, whereas the cultivar that showed greater Cat2 gene expression and had low H2O2 and MDA contents tolerated Cd stress effectively. Fruit quality of cv. Nagina was better than cv. Roma. In this context, we have recorded greater ash, fiber and protein contents in cv. Nagina, while cv. Roma was inferior in this regard under cadmium toxicity.