Kinetics of iron transport into the leaf symplast during recovery from iron stress

Abstract

The iron concentrations of chloroplasts (isolated by nonaqueous methods) and of chloroplast lamellae (isolated by aqueous procedures) were determined and used to investigate the kinetics of iron transport across the plasmalemma into the leaf symplast during the recovery of sugar beet plants from iron stress due to iron deprivation. Iron concentrations in chloroplasts isolated by the nonaqueous procedure were greatly reduced during iron stress and recovered to over 200% of control levels within 24 h. Iron concentrations in lamellae from aqueous isolations increased significantly within 24 h of resupply and reached values in excess of control levels in 48–72 h. These results indicate that a substantial quantity of the iron that entered the leaf blade during the first 24–48 h of iron resupply crossed the plasmalemma. The effect appeared to be specific to iron because there was no evidence that manganese, zinc, and copper were transported into chloroplasts and lamellae in enhanced amounts.