SUPPLEMENTAL ULTRAVIOLET-B RADIATION DOES NOT REDUCE GROWTH OR GRAIN-YIELD IN RICE

Negative effects of enhanced UV-B radiation have been demonstrated in plants, but impacts under realistic held conditions remain uncertain. Adverse impacts to major crops, such as rice (Oryza sativa L.), that a re grown in areas with currently high ambient levels of UV-B, could ha ve consequences for food security. To address the response of rice to UV-B, we conducted an intensive and extensive series of field experime nts from 1992 to 1995 documenting the effects of supplemental UV-B (si mulating approximately 20% ozone depletion for the Philippines), using irrigated rice cultivars under tropical conditions. This multiseason study indicated that supplemental UV-B had no significant effects on r ice grain yield (including the yield components spikelet filling perce ntage, and 1000-grain weight) or growth parameters (plant height or pa nicles per square meter). The absence of UV-B effects was consistent a cross seasonal environment (four dry and three wet seasons), cultivar, and type of exposure system. Thus, rice yields are not likely to be a ffected by increases in UV-B under realistic field conditions.