Effects of Cd(2+) on seedling growth of garlic (Allium sativum L.) and selected physiological and biochemical characters.

In this study, we determined the effects of Cd(2+) (from 10(-5) to 10(-3)M) on the growth of leaves and roots of garlic seedlings in Hoagland's nutrient solution. We also characterized the influences of Cd(2+) on a few key cellular activities, e.g., antioxidant enzymes, content of malondialdehyde (MDA), composition of photosynthetic pigments and fluorescence properties of chlorophyll on day 5, 10 and 15. The results indicated that the presence of 10(-3)M Cd(2+), but not other tested Cd(2+) concentrations, significantly decreased the development of leaves and roots of the seedlings. This level of Cd(2+) increased the activities of antioxidant enzymes and the level of MDA. With the exception of carotenoid on day 5, the presence of 10(-3)M Cd(2+) showed no significant effects on the contents of photosynthetic pigments. Intermediate concentrations of Cd(2+) caused variable effects, ranging from lowering to increasing the pigments in garlic seedlings. The presence of 10(-3)M Cd(2+), but not other tested concentrations, decreased efficiency of energy harvesting associated with photosystem II as measured by the ratio of variable to maximum chlorophyll fluorescence of intact leaves. However, Cd(2+) generated no definitive trends on photochemical quenching. Possible significance of experimental findings in relation to Cd(2+) level in garlic seedling is discussed.