Effect of bicarbonate on uptake and translocation of 59 Fe in two grapevine rootstocks differing in their resistance to Fe deficiency chlorosis

Abstract

In order to study the effect of high bicarbonate concentration in the root medium on root Fe III reduction, Fe uptake and its translocation to the leaves, two rootstocks ( Vitis riparia Michx., susceptible, and 41 B ( Vitis vinifera L. cv. Chasselas x Vitis berlandieri Planch.), resistant to Fe deficiency chlorosis) were pre-cultivated in nutrient solutions with high and low Fe supply. After three weeks of preculture at low Fe, chlorosis symptoms occurred in both, Fe-resistant and Fe-susceptible genotypes. The Fe III reducing capacity by roots was enhanced at Fe deficiency in both genotypes, which was consistent with the increase of subsequent root uptake and translocation rates of 59 Fe. In the presence of bicarbonate in the solutions the Fe III reducing capacity, 59 Fe uptake and translocation rate decreased in both genotypes precultured with low re supply. The 59 Fe uptake and translocation rate, however, were significantly higher in the Fe chlorosis-resistant rootstock 41 B. These results clearly indicate that bicarbonate-induced Fe chlorosis in grapevine rootstocks is obviously caused by an inhibition of Fe uptake and translocation due to an inhibition of Fe III reduction by root cells. The fact that these processes were less inhibited in the chlorosis-resistant rootstock hints to genotypical differences in Fe acquisition by roots at high bicarbonate levels. These differences might be used in breeding programs to identify Fe chlorosis-resistant rootstocks.