Effect of bicarbonate and phosphate on iron chlorosis of grape vines with special regard to the susceptibility of two rootstocks. part II: Pot experiments

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Abstract
In pot experiments the influence of bicarbonate and phosphate on the upset of chlorosis in grapevine grafted on two rootstocks with different Fe‐efficiency was studied. Grapevine grafted with the susceptible rootstock showed severe symptoms of chlorosis in the bicarbonate trials, while those on Fe‐efficient rootstock remained green during the whole experiment. Bicarbonate reduced the iron concentration in both the leaves and stems of the susceptible plants, but not in the resistent ones. The accumulation of iron at the root surface in these trials were more pronounced in the susceptible than in the non‐susceptible rootstocks. The pH of the cytoplasm from chlorotic leaves was higher than from the green ones. The main effect of bicarbonate on the Fe‐nutrition of grapevine is believed to be due to an alkalinisation of the rhizosphere and the cytoplasm as well as, disturbing the enzymatic Fe‐reduction process.