Solar UV-B Exclusion Effects on Growth and Photosynthetic Characteristics of Wheat and Pea

Abstract

Increased UV-B radiation on the earth's surface due to depletion of stratospheric ozone layer is one of the changes of current climate-change pattern. A field experiment was conducted to study the effects of solar ultraviolet-B (UV-B) radiation on growth parameters, net photosynthesis and biochemical characteristics of wheat (Triticum aestivum) and pea (Pisum sativum) crop species. Plants grown under ambient UV-B radiation were compared with those grown without UV-B by excluding ambient UV-B radiation. To exclude solar ambient UV-B, the sunlight was filtered through a polyester film that selectively absorbed UV-B. For ambient UV-B effects, plants were grown under polyvinyl chloride (PVC) filters that transmitted the complete light spectrum. The results indicate increased shoot length, leaf area, dry matter accumulation, leaf area ratio and specific leaf weight in plants of both the crops grown without UV-B compared with those grown under ambient UV-B. The effect of UV-B exclusion was clearer in pea compared with that in wheat.Similarly, the rate of photosynthesis (measured as CO₂ exchange rate), chlorophyll content, nitrate reductase (NR) enzyme activity and sugar content were significantly higher in pea plants grown without UV-B radiation, while changes in wheat plants were marginal and insignificant. We conclude that monocot species may be less sensitive to increased solar UV-B due to ozone depletion compared with dicots.

Key Words:

• Chlorophyll
• growth
• nitrate reductase activity
• pea
• photosynthesis
• UV-B radiation
• wheat