Effects of UltravioletB Radiation and Its Interactions with Climate Change Factors on Agricultural Crop Growth and Yield

12 1 K. Raja Reddy , P.V. Vara Prasad , and Shardendu K. Singh

'Department of Plant and Soil Sciences, Box 9555, 117 Dorman Hall Mississippi State University, Mississippi State, MS 39762, USA E-mail: [email protected] edu 2Department of Agronomy, Kansas State University, Manhattan, KS 66506, USA E-mail: [email protected]

Abstract Crops are often exposed to multiple factors of climate change including: (1) enhanced ultraviolet-B (UV-B) radiation, (2) elevated carbon dioxide concentrations (CO2), and (3) episodes of elevated temperatures and water stress during critical stages of crop development. Our understanding of crop responses to individual climate change stress factors has significantly advanced in recent years. However, crop responses to a combination of stress factors are less understood and need attention. In addition to direct effects on various physiological, growth, and yield traits of plants, the interaction of plants with biotic factors (particularly insects and pathogens) will play an important role in determining crop productivity. The objective of this chapter is to provide a summary of crop responses to UV-B, CO2, temperature, drought, and a combination of multiple stresses. Exposure to above ambient UV-B radiation decreases crop productivity through negative effects on photosynthesis, growth, dry matter production, yield, and grain quality. Elevated CO2 often improves photosynthesis, growth, and yield of most crop species. Alternatively, exposure to both above optimum temperatures and water stress significantly decreases crop productivity and quality, particularly when stress occurs during sensitive stages (reproductive phase) of crop development. The positive effects of elevated (CO2) on photosynthesis and growth do not generally overcome the negative effects of UV-B radiation, elevated temperatures, or water stress on productivity and quality of grain crops. Crop species and cultivars within crop species vary in their responses to both individual and a combination of stress factors, suggesting a scope for genetic improvement. Further research should be focused on breeding for tolerance to multiple stresses of regional and local importance. An increased knowledge of crop responses to multiple stresses and genetics may also improve crop simulation models resulting in a better understanding, prediction and management of crops in a changing environment.

Keywords climate change, crop growth and yield, drought stress, genetic variability, multiple abiotic stresses, temperature

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