Characterization of pollen tube growth and induced molecular changes in Berasicca napus L. by UV-B treatment

During the past few decades, the problems caused by the stratospheric ozone reduction has stimulated remarkable research on higher plant responses to UV-B radiation. Depletion of the stratospheric ozone layer is leading to an increase in ultraviolet-B (UV-B: ۲۸۰–۳۲۰ nm) radiation reaching the earth’s surface. This has raised interest in the possible consequences of increased UV-B levels on plant growth and development and the mechanisms underlying these responses. Although the effects of UV-B are now well characterized at the physiological level, little is known about the involved cellular and molecular mechanisms. Recent studies have shown that UV-B affects a number of important physiological processes, such as photosynthesis, through effects on gene expression. However, little research has addressed the reproductive biology of plants. The purpose of this study was to investigate the effects of UV-B radiation on reactive oxygen species (ROS) accumulation and antioxidant defense system in relation to germination and pollen tube growth of canola (Brassica napus L.). Our results illustrated that increased UV-B radiation decreased the pollen germination rate and tube length in vitro. Production of superoxide anion radical (O۲•−) and hydrogen peroxide (H۲O۲) increased by UV-B radiation treatment, and their accumulation resulted in lipid peroxidation. The activities and gene expression of superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) were decreased by enhanced UV-B radiation. The increased ROS and lipid peroxidation, as well as decreased antioxidant activities may be attributed to the effects of UV-B radiation on pollen germination and tube growth.

Keywords:

Brassica napus L , pollen germination , reactive oxygen species , UV-B radiation