PLANTS OF ZEA-MAYS L DEVELOPED UNDER ENHANCED UV-B RADIATION .1. SOME ULTRASTRUCTURAL AND BIOCHEMICAL ASPECTS

Zea mays L. cv. LG12 plants were grown under controlled conditions in growth chambers with and without UV-B radiation. After 10 days of irradiation it was found that UV-B provoked an increase in flavonoid content and even the synthesis of some new ones as observed by chromatography. Total protein content was decreased when expressed on a dry weight basis; however, SDS-PAGE showed that UV-B promoted the increase of some soluble proteins and also interfered with some insoluble ones. Chlorophyll level was also affected as well as the anatomy and ultrastructure of the leaves. Adaxial epidermal cells collapsed and cytoplasm of chlorophyllous cells showed abundant vesiculation, increased rough endoplasmic reticulum and dictyosome associated vesicles in mesophyll cells. The fractional volume of chloroplasts was decreased while the opposite was observed for fractional volume of starch relative to these organelles. The timing of flowering was not affected but the height of plants, the leaf area and the leaf thickness were reduced by UV-B radiation. The results of this study showed that despite the interference of the UV-B radiation on the physiology and morphology of the plants they did attain the reproductive stage and reached maturity.