Impact of elevated carbon dioxide and different nitrogen doses on grain quality of rice (Oryza sativa L.)

Abstract

Rice (Oryza sativa L.) is one of the most important food crops in the world and is the staple food for nearly half of the world‟s population [1]. Global climate change is one of the biggest challenges of the twenty first century [2]. Improvements in rice productivity and quality must be achieved under projected climate change conditions, which will have significant impacts on crop yield and quality [3]. Rising atmospheric [CO2] and related CO2 fertilization effect may have regulating effects on numerous aspects of growth, plant physiology and biochemistry in various crops [4-7]. This could have significant implications for public health and nutritional securities of nation. Elevated [CO2] will have positive effects on biomass and grain yield by promoting photosynthesis [7], whereas negative effects are expected on grain quality. Grain quality get affected in terms of nutrition (protein content, N, P, K, Fe and Zn) [8], appearance (grain length, width, grain chalkiness and hardness) and cooking properties (Amylose content, Gelatinization Temperature, Gel Consistency) [9, 10]. Rice grains produced under elevated CO2 exhibited lower mineral (viz., N, P, Zn and Cu) and protein contents, while amylose content was higher than in those grown under ambient CO2 [11, 12], produced harder grains grown under elevated CO2. Some experiment showed that FACE decreased the protein content, increased maximum viscosity, but did not change amylose content [13]. Further it has been reported that only N concentration in rice grains was negatively affected by CO2 enrichment, with other macro- (viz., P, K, Mg, S) and micronutrient contents (viz., Zn, Mn, Fe, B, Mo) remaining unaffected [14]. Further Rice quality is determined not only by its nutritional value but also by its appearance, milling performance, and cooking characteristics. Although these quality attributes differ, depends upon its end use but appearance, milling and the cooking quality of the rice are of prime concern among consumers [9, 11, 13, 15]. Their findings indicate that detailed knowledge of effect of elevated CO2 on rice grain quality response to elevated CO2 is still lacking and inadequate to the date.