KINETICS OF K+ ABSORPTION BY VARIOUS WHEAT VARIETIES

A solution culture experiment indicated that wheat varieties varied in kinetic parameters of K+ absorption. The smallest values of Michealis constant for K+ absorption (Km) was found with var. Hongai 1. and maximum rate of K uptake (Imax) was found with Hongmang 22. The greatest value of km for K+ absorption was obtained with Manyang 11 and the greatest value of Imax was observed with Fan 6. The compensa-, tion concentrations for K+ uptake (Cmin3.44mol/L) by the tested wheat varieties were lower than K+ concentrations in soil solutions of commonly cultivated soils. This result showed that K+ contents in many soil solutions are adaptable to the requirement for K+ uptake by wheat. Moreover, NH4+ inhibited K+ uptake in contrast to NO3- , rare earth and indole acetic acid (IAA) which promoted K absorption. No obvious effect of urea on K+ uptake was observed. The reason for the inhibitation by NH4+ was that Km for K+ uptake was increased. The promotion by NO3- was accounted for by Imax increment. The enhancement of K+ uptake by rare earth can be explained by Km decrement. IAA Promoted H+ efflux which caused increasing in the rate of K+ uptake.