Morpho-physiological responses of maize cultivars exposed to chromium stress

Abstract

Chromium (Cr) is non-essential element and one of the hazardous heavy metals present in environment. Among cereals, maize is used as a source of food both for plants and humans and is also being cultivated on metal-contaminated soils mainly to feed the increasing population. Therefore, the screening of low Cr accumulating maize varieties could be an environment friendly option mainly for Cr-contaminated soils. For this purpose, seeds of eight maize cultivars; 6103, Gorilla, Garanon, p1574, 8711, 6525, 6142 and 9108 were grown in soil and the plants were irrigated with different Cr concentrations after two weeks of germination for the next three weeks to reach the selected final Cr concentrations in soil (0, 100 and 500 μM). Plants were harvested after eight weeks of sowing and different physiological and morphological traits of plants were measured including photosynthesis, biomass, growth, activity of antioxidant enzymes and oxidative stress markers. Results showed that increasing Cr concentration in the soil caused a reduction in all selected physiological and morphological parameters of maize plants. Chromium stress enhanced the electrolyte leakage, malondialdehyde, hydrogen peroxide while the production of antioxidant enzymes; catalase, peroxidase, superoxide dismutase, ascorbate peroxidase, varied with the maize cultivars in shoots and roots of maize. Furthermore, Cr addition in the growth medium increased the Cr concentration in leaves and roots in a dose dependent manner. The response of maize cultivars varied with the studied cultivars and Cr concentrations applied. Among studied cultivars, 6103 and 9108 accumulated the lowest and the highest Cr concentrations in different parts, respectively. This showed that cultivar 6103 might be used for the Cr-contaminated soils without loss in biomass and to avoid Cr entry to the food chain. However, in depth field studies are needed in future research before the practical application.