Abstract
The young tissues in salt-sensitive plants are less damaged even if they contain higher Na contents than aged tissues. The mechanisms to protect the young tissues from salt-induced damages are still unclear. Because salt tolerance is due to higher antioxidant enzyme activities, we investigated the changes in the activities of antioxidant enzymes in the apical and basal parts of rice leaves under salinity. The damages were observed only in the aged apical part, whereas Na contents increased comparably in both parts. In the apical part, the activities of CAT and water-water-cycle enzymes were reduced under salinity. However, in the young basal part, CAT activity was enhanced while the activities of water-water cycle enzymes were maintained. These results suggest that young tissues in salt-sensitive plants have the ability to resist to salt stress by effectively scavenging active oxygen species and this ability is lost as the tissues become older.
