Abstract
Sugar alcohols (mannitol and sorbitol) may cause oxidative damage in plants if used in higher concentration. Our present experiment was undertaken to study physiological and metabolic responses in cotton (Gossypium hirsutum L.) callus against mannitol and sorbitol higher doses. Both markedly declined mean values of relative fresh weight growth rates with the increase in their concentration intensities. The overall protein and malonaldehyde (MDA) contents increased in the stressed-shocked cells. Also, the mean values of various antioxidants such as superoxide dismutase (SOD), peroxidase (POD), ascorbate peroxidase (APX) and calalase (CAT) quantitatively improved over their respective controls. As a whole, MDA contents were higher in magnitude than that of different antioxidant enzymes. Also values of relative increase in case of POD were higher as compared to SOD showing the ability of cotton callus culture to scavenge H2O2 produced as a result of the activity of SOD. Our results show that both agents caused greater damage to the membranous structure in comparison to less activation of the antioxidants. As a whole, the overall change regarding fresh weight growth rates was less after 14-day stress regime, while the mean values of the antioxidant enzymes activities were lower after the 28-day stress period. Such decrease conveys the message that less reactive oxygen species (ROS) might have been produced.
Highlights
Exposure of plant species to various environmental stresses results in the production of reactive oxygen species (ROS) in chloroplasts, mitochondria and microbodies of plant cells
In order to study the influence of sugar alcohols stresses on cotton callus growth, the percent values of relative fresh weight growth rate of cotton callus culture were analyzed (Table 1)
The osmolyteinduced enhancement of POD activity in Coker 312 callus culture indicated that it had a higher capacity for the decomposition of H2O2 generated by superoxide dismutase (SOD)
Summary
Exposure of plant species to various environmental stresses results in the production of reactive oxygen species (ROS) in chloroplasts, mitochondria and microbodies of plant cells. To avoid and alleviate such damage, plants have evolved specific protective antioxidant enzymes system comprised of: (a) low molecular weight antioxidants (αtocopheroal and β-carotene), and water-soluble reductants (e.g. glutathione and ascorbate); and (b) antioxidative enzymes like superoxide dismutase, peroxidase, ascorbate peroxidase and calalase. These enzymes are the most important components in the scavenging system of ROS (Meloni et al, 2003). Superoxide dismutase (SOD) provides the first line among the antioxidant defense system as it dismutates
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