Activities of some enzymes associated with oxygen metablolism, lipid peroxidation and cell permeability in dehydrated Malus micromalus seedlings

Measurements were made on the relative water content, cell permeability, superoxide dismutase (SOD) activity, catalase (CAT) activity and malondialdehyde (MDA) content in Malus micromalus seedling during dehydration in vitro in whole seedling and during dehydration in culture of different PEG 6000 concentration. The results indicated that SOD and CAT activities increased during dehydration from 0 to 3 h and decreased after dehydration for 3 h; MDA content decreased before 3 h dehydration and the MDA content and cell permeability increased significantly after 3 h in various treatments of dehydration (in vitro and in whole seedling). SOD and CAT activities in 20 days seedlings were higher than those in 10 days seedlings whereas the MDA content and cell permeability in 20 days seedlings were lower than those in 10 days seedlings. In 20 days seedlings during dehydration in vitro, SOD and CAT  activities in leaves were higher than those in root and the latter was higher than those in stem. However, the MDA content and cell permeability in leaves were lower than those in root which in turn were lower than those in stem. Significant correlations and regressions exist among the changes observed in the SOD activity, CAT activity, MDA content, cell permeability and the relative water content.