Semi-arid Crop Responses to Atmospheric Elevated CO2 (original) (raw)

Semi-arid tropics host most of the poor and small-holding farmers of the developing world. Global warming is seen largely as a consequence of continuous increase in the emission of carbon dioxide and other greenhouse gases into the atmosphere leading to unusual changes in global temperatures and rainfall patterns. This in turn is expected to increase the water scarcity in the environment, affecting plant growth and metabolism. In this context, we reviewed semi-arid crop responses to elevated CO 2 levels in terms of growth, yield components, physiological, biochemical and molecular changes. Predicted rise of carbon-dioxide in the atmosphere may benefit the plants by increasing the crop water use efficiency and net photosynthesis leading to greater biomass, yield and harvest index. C 3 and C 4 crop plants vary in their degree of response to elevated CO 2 , which will likely affect the proportion of land area occupied by these crops in future. Stomatal conductance will probably be reduced at higher CO 2 concentrations reducing transpiration per unit leaf area and consequently increasing the leaf temperature. The high CO 2 is an ameliorative of the adverse effects of drought and acts by altering the plant, biochemical and molecular systems. Understanding of the direct effects of elevated CO 2 and its interactions with the other climate variables is needed in order to predict the impact of climate change scenarios on crop growth and food security in future.