PLANTS OF ZEA-MAYS L DEVELOPED UNDER ENHANCED UV-B RADIATION .1. SOMEULTRASTRUCTURAL 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 irra diation it was found that UV-B provoked an increase in flavonoid conte nt and even the synthesis of some new ones as observed by chromatograp hy. Total protein content was decreased when expressed on a dry weight basis; however, SDS-PAGE showed that UV-B promoted the increase of so me soluble proteins and also interfered with some insoluble ones. Chlo rophyll level was also affected as well as the anatomy and ultrastruct ure of the leaves. Adaxial epidermal cells collapsed and cytoplasm of chlorophyllous cells showed abundant vesiculation, increased rough end oplasmic reticulum and dictyosome associated vesicles in mesophyll cel ls. The fractional volume of chloroplasts was decreased while the oppo site was observed for fractional volume of starch relative to these or ganelles. The timing of flowering was not affected but the height of p lants, the leaf area and the leaf thickness were reduced by UV-B radia tion. The results of this study showed that despite the interference o f the UV-B radiation on the physiology and morphology of the plants th ey did attain the reproductive stage and reached maturity.