Effects of supplementary ultraviolet-B irradiance on maize yield and qualities: a field experiment.

Stratospheric ozone depletion has caused an increase in the amount of ultraviolet-B (UV-B) radiation reaching the earth's surface. Numerous investigations have demonstrated that the effect of UV-B enhancements on plants includes reduction in grain yield, alteration in species competition, susceptibility to disease and changes in plant structure and pigmentation. Many experiments examining UV-B radiation effects on plants have been conducted in growth chambers or greenhouses. It has been questioned whether the effect of UV-B radiation on plants can be extrapolated to field responses from indoor studies because of the unnaturally high ratios of UV-B/ultraviolet-A radiation (320-400 nm) and UV-B/photosynthetically active radiation (PAR) in many indoor studies. Field studies on UV-B radiation effect on plants have been recommended to use the UV and PAR irradiance provided by natural light. This study reports the growth and yield responses of a maize crop exposed to enhanced UV-B radiation and the UV-B effects on maize seed qualities under field conditions. Enhanced UV-B radiation caused a significant reduction in the dry matter accumulation and the maize yield in turn was affected. With increased UV-B radiation the flavonoid accumulation in maize leaves increased and the contents of chlorophyll a, b and (a + b) of maize leaves were reduced. The levels of protein, sugar and starch of maize seed decreased with enhanced UV-B radiation, whereas the level of lysine increased with enhanced UV-B radiation.