BIOCHEMICAL AND ULTRASTRUCTURAL-CHANGES IN POLLEN OF ZEA-MAYS L. GROWN UNDER ENHANCED UV-B RADIATION

The influence of ultraviolet-B (UV-B) radiation on the development of the male gametophyte was studied in Zea mays L. cv. LG12 grown in a gr owth chamber under PAR light supplemented with UV-B radiation and comp ared with a second set of plants grown under PAR light. Pollen samples collected from both groups of plants were cultured on germination med ium and it was found that W-B had no effect on pollen germination. Tot al pollen protein content was not affected but W-B absorbing pigments increased. Some ultrastructural alterations were observed in pollen an d pollen tubes, in particular large amounts of electron dense deposits were seen throughout the cytoplasm and in association with the pollen wall. In mature spikes of UV-B treated plants, anthers retained numer ous pollen grains in their loculi while anthers of control plants were almost empty. UV-B treatment delayed flowering by 2-3 d. These result s show that UV-B treatment of maize plants interferes with flowering, pollen ultrastructure and anther maturation even though pollen germina tion is unaffected. The significant increase of UV-B absorbing pigment s in pollen grains could represent a defence mechanism that enables pl ants to complete their reproductive cycle. (C) 1998 Annals of Botany C ompany.