Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/6/2013
Publication Date: 7/8/2013
Citation: Reddy, R.K., Singh, S.K., Koti, S., Kakani, G.V., Zhao, D., Gao, W., Reddy, V. 2013. Quantifying the effects of corn growth and physiological responses to Ultraviolet-B radiation for modeling. Agronomy Journal. 105(5):1367-1377. Interpretive Summary: Ultraviolet-B (UV-B) radiation is an integral part of sunlight that reaches the surface of the Earth. Even though UV-B represents a small fraction of total solar radiation, exposure to UV-B radiation adversely affects almost all living organisms including agricultural crops such as maize (corn). The amount of UV-B radiation has been increased in the recent past and predicted to increase in the future. Maize is grown worldwide for food, forage and bio-fuel. UV-B radiation causes harmful effect on maize growth, development and yield. It is important to understand the response of maize crop to a range of UV-B radiations for the view point of agronomy and crop modeling. The results indicated that the maize growth and developments process are more sensitive than photosynthetic process under both current and projected UV-B radiation. The mathematical relationships between dosage of UV-B radiation and maize crop growth obtained from this work should be useful and can be incorporated into mechanistic maize simulation models, which previously account for variations in temperature as well as water and nutrient stresses. Models such as CERES-Maize and MaizSim can be exploited to predict yields and to improve management practices under present and future enhanced UV-B radiation levels in production environments.
Technical Abstract: To understand the consequences of rising levels of Ultraviolet-B (UV-B) radiation on maize (Zea mays L.), two experiments were conducted using sunlit plant growth chambers at a wide range UV-B radiation. Maize cultivars Terral-2100 and DKC 65-44 were grown in 2003 and 2008, respectively, at four levels of (0, 5, 10, and 15 kJ m-2 d-1) UV-B from 4 days after emergence to 43 days under optimum nutrient and water conditions. An inverse relationship between many growth process and dosage of UV-B radiation were recorded in both experiments. The reduced plant heights were due to shorter internodes lengths rather than fewer internodes and the total leaf area was less due to smaller leaves. Lower biomass under enhanced UV-B was closely related to both smaller leaf area and lower photosynthesis. Critical UV-B limit defined as 90% of optimum or control were derived from the UV-B response indices for the parameters studied. The critical limits for stem extension and leaf area expansion were lower in both cultivars (1.7 - 3.5 kJ m-2 d-1 UV-B) than the critical limit for leaf number (> 15 kJ m-2 d-1 UV-B) and photosynthetic processes (4.2 - >15 kJ m-2 d-1 UV-B), indicating that expansion or extension rates of organs were the most sensitive to UV-B radiation. Cultivar Terral-2100 exhibited greater sensitivity to UV-B radiation than DKC 65-44. Thus, both current and projected UV-B radiation can adversely affects maize growth. An attempt was made to quantify and develop UV-B radiation-dependent functional algorithms that can be used in developing mechanistic crop simulation models.