Chapter 6 - Crop production in response to elevated CO2: grain yield and quality

Abstract

The concentration of atmospheric carbon dioxide (CO2) has almost doubled since the preindustrial era due to global climate change and is expected to further increase if the current emission rates are not controlled. The impacts of elevated CO2 (e[CO2]) on growth, development, and yield of plant species, particularly crops, are very important concerns for the scientist. This is due to dynamic implications on global agricultural production and food security in the climate change scenario. Crops respond to the e[CO2] by stimulating the photosynthetic rate. which boosts crop yield. Higher levels of atmospheric carbon act like a carbon fertilizer for the plants and results in an increase in plant growth and productivity. Cereal crops grow larger in size and exhibit faster growth rates under e[CO2], and biomass production becomes higher. Crops have evolved strategies to enhance their physiological performance by increasing water use efficiency and reducing the transpirational water loss as well as lowering stomatal conductance under e[CO2]. C3 plants exhibit considerably higher increases in yield due to e[CO2] ranging from 20% and 35% as compared to C4 crops with only 10% to 15%. e[CO2] influences the qualitative attributes of crops, including the concentration of nutrients, which are fundamental food quality attributes having diverse implications on agricultural production, market value of crops as well as impacts on human health. Sharp declines are projected in the protein content and free amino acid of cereals under e[CO2] conditions. Under realistic field conditions experiments, free-air CO2 enrichment technology revealed significant increases in the photosynthesis activity, leaf carbohydrates, starch and sugars whereas the concentration of nitrogen per unit leaf mass has been found to decrease. The relative yield responses of grain crops under e[CO2] might increase under limiting nutrient and water conditions due to physiological adaptations. The major C3 cereals, including wheat and rice, undergo major shifts in physiological responses and C:N metabolism in response to e[CO2], However, a reduction in nutritional quality under e[CO2] appears to be a major challenge.