Kinetics of zinc uptake by two rice cultivars

Summary Rice (Oryzae sativa L.) cultivars differ widely in their susceptibility to zinc (Zn) dificiency. Excised root apices of cv IR26 actively absorbed Zn at a rate twice that of cv M101 roots. This difference in Zn uptake rates could not be attributed to greater root surface area in cv IR26 as compared to cv M101. The maximum rates of Zn uptake (Vmax) and the Km values also differed markedly between these two cultivars. Roots of cv M101 have a two-fold greater affinity for Zn than do those of cv IR26. Leaf blade tissues of IR26 and M101 rice absorbed Zn at similar rates. Rice cv IR26 readily develops Zn deficiency symptoms in hydroponic culture but cv M101 rarely does so.