Effects of UV‐B Radiation on Net Photosynthesis of Some Crop Plants¹

Abstract

Thirteen crop plants were subjected to an enhanced ultraviolet “B” (UV‐B) radiation (280 to 320 nm) regime that simulated a 0.19 atm cm ozone level, solar angle 55° (approximately 50% ozone depletion at 30° N latitude), to determine their susceptibility to photosynthetic impairment. As evidenced by net CO 2 uptake and dry weight measurements, these plants exhibited a wide range of response to enhauced levels of UV‐B radiation. These species were classified either as “sensitive” (pea, Pisum sativum L.; collard, Brassica oleracea L., var. acephala ; cabbage, Brassica oleracea L., var. capitata ; soybean, Glycine max L.; and oat, Avena sativa L.), “moderately sensitive” (tomato, Lycopersicum esculentum L.; sorghum Sorghum bicolor L.; rye, Secale cereale L.; and rice, Oryza sativa L.), or “tolerant” (corn, Zea mays L.; digitgrass, Digitaria decumbens Stent.; pearl millet, Pennisetum americanum (L.) K. Schum.; and peanut, Arachis hypogaea L.) in respect to their sensitivity to UV‐B radiation. Plants grown in growth chambers with the same UV‐B enrichment but a lower irradiance of visible light (50 W.m ‐2 ) showed greater photosynthetic impairment than did greenhouse‐grown plants. This was postulated to be due to photorepair under greenhouse conditions.