UV-B-Induced Effects upon Cuticular Waxes of Cucumber, Bean, and Barley Leaves

Abstract

Barley, bean, and cucumber seedlings were grown in a growth chamber with white light and low levels of UV-B radiation. Cuticular waxes found in barley leaves were five times greater than in bean or cucumber leaves based on leaf area. Predominant compounds identified were primary alcohols in barley wax, primary alcohols, and wax monoesters in bean wax, and alkanes in wax from cucumber leaves. Irradiation with enhanced levels of UV-B radiation caused an increase of total wax by about 25% in all plant species investigated. The wax composition was not markedly affected with respect to these wax classes. However, aldehyde content, detected as a minor constituent of cucumber and barley wax, increased twofold with enhanced UV-B radiation. The distribution pattern of the homologs within each wax class was different at both low and enhanced UV-B levels. In general, the distribution of the homologs was shifted towards shorter acyl chain lengths in wax classes of leaves exposed to enhanced UV-B levels. This effect was most apparent in cucumber wax, and less in bean or barley wax.

It is assumed that increased amounts of epicuticular waxes may have a function in attenuating enhanced UV radiation via UV reflectance and scattering.