Effect of Fe plaque on Zn uptake and rhizosphere Zn acquisition of rice lines with different Zn efficiency

Abstract

By using the dithionite-citrate-bicarbonate technique (DCB) to extract iron plaque from the rice plants grown either in stagnant solution culture or in the soil, we found that 50% of Zn in the rice root was associated with Fe plaque at the root surface. Although applied Zn was constant in all treatments, Zn associated with Fe plaque (ZnP) and Zn content in the shoot and root varied according to the concentration of Fe in the solution and rice cultivars. Growth and Zn uptake of IR8192 (IR81*, Zn efficient) was higher than the inefficient IR26 at all Fe levels. Shoot and root Zn concentration was generally lower in IR81* than in IR26, confirming that IR81* is more efficient than IR26 due to lower requirement of Zn, the so-called internal efficiency. However, ZnP did not show any negative effect on shoot Zn uptake, suggesting rhizosphere acquisition of Zn from the Fe plaque. The result also suggests that ZnP should be excluded for better assessment of total Zn content in the plant.