ADVANCES IN CROP RESPONSES TO ENHANCED UV-B RADIATION

The increased ultraviolet-B (UV-B) radiation (280-320 nm) on the Earth's surface is one of the most important concerns of global change. This concern is primarily because increased UV-B radiation has been unambiguously shown to be responsible for the majority of harmful effects on aquatic as well as terrestrial organisms, and thus influence ecological interactions. For the past 4 plus decades, many studies have been conducted on the damaging effects of elevated UV-B radiation on plants. These studies have shown a diverse range of responses to UV-B radiation, and might be in general arbitrarily divided into two classes, photomorphogenic and stress responses at the morphological, physiological, biochemical and molecular levels. Crop plants evolved different adaptive or defensive mechanisms to UV-B radiation, including accumulation of UV-absorbing sunscreens, production of enzymatic and non-enzymatic antioxidants, changes of phytohormones or activation of DNA-repairing enzymes. A diagram illustrating the general responses of UV-B radiation and complexity of the interactions among factors was developed. Three urgent specific researches are proposed, which might provide opportunities for genetic engineering and possibility of breeding to deal with potential crop yield reductions due to elevated UV-B in agricultural systems, and thus will play a major role in determining the crops future.