VARIATION IN UV‐B SENSITIVITY IN PLANTS FROM A 3,000‐m ELEVATIONAL GRADIENT IN HAWAII

Interest in the potential consequences of stratospheric ozone depletion has led to numerous studies that have evaluated the effects of ultraviolet‐B (UV‐B) radiation on plant growth and productivity. However, few studies have been conducted on plants from natural ecosystems. Differences in solar UV‐B radiation along latitudinal or elevational gradients may have resulted in plants from diverse habitats developing contrasting sensitivities to UV‐B radiation. In this study, seeds were collected along a 3,000‐m elevational gradient in Hawaii and then germinated and grown in an unshaded greenhouse with either no UV‐B radiation or one of two daily UV‐B irradiances, 15.5 or 23.1 kj m 2 . Seedlings were grown for 12 weeks and harvested to determine whether UV‐B radiation altered plant biomass. The responses to UV‐B radiation varied among species, but, in general, sensitivity to UV‐B radiation was reduced as the elevation of seed collection increased. Of the 33 species tested, UV‐B radiation significantly reduced plant height in 14 species and biomass in eight species. Biomass increased in four species grown under UV‐B radiation. This study provides clear evidence that natural plant populations exhibit wide variation in UV‐B radiation sensitivity and that this variation is related to the natural (ambient) UV‐B radiation environment in which these plants grow.