[Effect of HCO3- on root growth and nutrient absorption of different rice genotypes]

Solution culture experiments with Zn-inefficient cultivar (IR26) and the Zn-efficient cultivar (IR8192-31-2) were conducted to study the effect of HCO3- on the root growth and nutrient absorption of different rice cultivars. The results showed that HCO3- strongly inhibited the root growth of Zn-inefficient cultivar especially at low Zn concentration. In contrast, that of Zn-efficient cultivar was slightly stimulated by HCO3- at low Zn concentration. HCO3- not only inhibited Zn absorption of Zn-inefficient cultivar, but also inhibited its absorption of Fe, Mn, Cu, implying that there was no specific inhibition of HCO3- on Zn absorption. These results demonstrated that the inhibition of root growth by HCO3- was likely to be the initial action of HCO3- in inducing Zn deficiency in lowland rice. With treatment of bicarbonate, Zn concentrations in upper and lower leaves of the Zn-efficient cultivar and their ratios were higher than those of the Zn-inefficient cultivar. The results showed that the Zn-efficient cultivar could transport more zinc from lower leaves to upper leaves, which might be-one of mechanisms that the Zn-efficient cultivar adapted to zinc deficiency in calcareous soil.