EFFECT OF IRON DEFICIENCY STRESS ON IRON-REDUCTASE ACTIVITY AT PLASMALEMMA OF APPLE ROOT CELLS

ABSTRACT

Using two phase systems, plasma membrane (PM) of root cells was separated and purified from Malus xiaojinensis Cheng et Jiang, and iron (Fe)-reductase activities on PM analyzed, under conditions of both the normal Fe level (+Fe) and the Fe deficiency stress (−Fe) were compared. The results showed that FeCN-reductase on PM depended on NADH as the electron donor. The FeCN-reductase activity was 2.66 μmol L⁻¹ mg⁻¹ min⁻¹ at +Fe, while the reductase activity was 4.92 μmol L⁻¹ mg⁻¹ min⁻¹ at −Fe. Fe-EDTA-reductase could depend on either NADH or NADPH as the electron donor. There were no differences in Fe-EDTA-reductase activities on PM at either +Fe or −Fe, when the electron donor was NADPH. NADH being as the electron donor, however, the Fe-EDTA-reductase activity was 4.06 μmol L⁻¹ mg⁻¹ min⁻¹ at −Fe, while the reductase activity was 2.73 μmol L⁻¹ mg⁻¹ min⁻¹ at +Fe. Therefore, Fe³⁺ reduction on PM by Fe-reductase systems could be induced and also enhanced in M. xiaojinensis by Fe deficiency stress, which indicated that M. xiaojinensis had a stronger Fe deficiency stress response, and it was an Fe-efficient fruit genotype.

ACKNOWLEDGMENTS

This research was supported partially by the Natural and Science Funding Committee of Beijing Municipality and the State Ministry of Education of China.