Iron distribution in vine leaves with HCO3‐induced chlorosis

The objective of the investigation was to examine whether iron chlorosis in grape vine grown on calcareous soils was related to the Fe distribution in the leaf. Leaf samples collected from three different sites showed in most cases higher Fe contents in the chlorotic leaves as compared with healthy leaves. The solubility of leaf Fe in diluted HC1, however, was lower in chlorotic leaves than in green leaves. Enzymatic dissolution of leaves into vascular tissue, intercostal cells and chloroplasts revealed that the Fe content in the intercostal cells of green leaves was significantly higher than in the intercostal cells of chlorotic leaves. In addition, the intercostal cells of chlorotic leaves had extremely high Ca and P contents. The P content of green and chlorotic leaves was not related to the level of available P 1n the soil. It is, therefore, concluded that the high P content in chlorotic leaves is the sequence and not the cause of Fe chlorosis. On each of the three sites investigated, higher clay contents were found under chlorotic grape vine plants than under healthy ones. It is assumed that because of this higher clay content, soil compaction may occur, resulting in an accumulation of CO2 and in an increase of the HCO3 ‐ concentration in the soil solution.