Frequency distribution of zinc in leaves with and without zinc-deficiency symptoms, all collected from a single orange tree [Citrus sinensis, Citrus aurantium]

Leaves with zinc-deficiency symptoms had a lower Zn concentration than corresponding leaves without symptoms and of the same age from the same orange (Citrus senensis L.) tree on sour orange (C. aurantium L.) rootstock grown in Rhodes, Greece. There was considerable overlap, however, with the frequency distribution of each group approximating a normal curve. But both kinds of leaves combined showed a more normal distribution. Some leaves with symptoms had higher zinc concentrations than some without symptoms. There was a threefold range in Zn concentration for each group of leaves. Zinc-deficient leaves had less phosphorus, calcium, and manganese and more iron, aluminum, silicon, and titanium (the so-called dust elements) than did leaves with no deficiency symptoms. Some of these elements gave normal curves for both Zn-deficient and non-Zn-deficient leaves.