Effect of bicarbonate on uptake and translocation of ⁵⁹Fe 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 ⁵⁹Fe. In the presence of bicarbonate in the solutions the Fe^III reducing capacity, ⁵⁹Fe uptake and translocation rate decreased in both genotypes precultured with low re supply. The ⁵⁹Fe 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.