Evaluation of physiological and biochemical responses of two rice (Oryza sativa L.) cultivars to ambient air pollution using open top chambers at a rural site in India Richa Rai, Madhoolika Agrawal ⁎ Ecology Research Laboratory, Department of Botany, Banaras Hindu University, Varanasi ARTICLE DATA ABSTRACT Article history: Received 3 April 2008 Received in revised form 9 September 2008 Accepted 9 September 2008 Available online 28 October 2008 Air pollutant concentrations are rising in India, causing potential threats to crop production. As air pollutants are known to interfere with physiological processes, this study was conducted to assess the relative responses of physiological and biochemical characteristics of two cultivars of rice (Oryza sativa L. cv. Saurabh 950 and NDR 97) leading to variable yield responses. Twelve hour monitoring of ambient concentrations of SO 2 , NO 2 and O 3 in filtered chambers (FCs), non-filtered chambers (NFCs) and open plots (OPs) showed that O 3 was the main pollutant at the experimental site. Ozone concentrations often exceeded 40 ppb during anthesis but not during the vegetative growth period. Photosynthetic rate (Ps), stomatal conductance (g s ) and Fv/Fm ratio, superoxide dismutase (SOD) and peroxidase (POD) activities and photosynthetic pigments, ascorbic acid, total phenolics and protein contents were assessed at different developmental stages and yield of grains were quantified. Lipid peroxidation, SOD and POD activities, ascorbic acid and total phenolics were higher, whereas Ps, g s , Fv/Fm ratio and contents of protein and photosynthetic pigment were lower in plants of NFCs as compared to FCs. Yield decreased significantly in both cultivars grown in NFCs. NDR 97 showed less reductions in physiological characteristics, photosynthetic pigments and protein, but a greater increase in the antioxidative defense system as compared to Saurabh 950. Yield reduction was higher in NDR 97 than in Saurabh 950. This suggested that NDR 97 utilized more photosynthate in maintaining the metabolic machinery against O 3 stress leading to lower translocation of photosynthate to reproductive parts. The study concluded that under natural field conditions, physiological and biochemical responses of plants varied with pollutant concentrations leading to different translocation strategies in plants, modifying their yield responses. NDR 97, a fast growing and high yielding cultivar was more sensitive than slow growing Saurabh 950. © 2008 Elsevier B.V. All rights reserved. Keywords: Open top chambers Ozone Sulphur dioxide Nitrogen dioxide Antioxidants Rice 1. Introduction Ambient air pollution, particularly O 3 has been shown to reduce the growth and economic yield of a wide range of major crop species of North America and Europe (Heck et al., 1988; UNECE ICP vegetation, 2001). Air pollutant concentrations are increasing tremendously in urban, suburban and even rural areas of developing countries due to rapid economic transfor- mations led by industrialization, increasing urban popula- tions, a rising number of motor vehicles and ineffective pollution control regulations. Assessment of ground level O 3 monitoring data from different areas of Asia clearly showed that O 3 concentrations have already reached to the levels which can significantly reduce agricultural productivity across SCIENCE OF THE TOTAL ENVIRONMENT 407 (2008) 679 – 691 ⁎ Corresponding author. E-mail address: madhoo58@yahoo.com (M. Agrawal). 0048-9697/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.scitotenv.2008.09.010 available at www.sciencedirect.com www.elsevier.com/locate/scitotenv