Effects of major global climate change components on nutritional physiology and biofortification of wheat

Increasing atmospheric carbon dioxide (CO2) and episodes of agricultural drought are two of the important aspects of climate change. In general, elevated CO2 enhances crop biomass production and yield along with mitigating the adverse effects of drought stress. However, this favorable effect of elevated CO2 on plants is highly dependent on the immediate availability of mineral nutrients. Moreover, elevated CO2 is associated with decreased nutrient (e.g. Zn, Fe and N) concentrations in vegetative tissues as well as the grain. The purpose of this project was to investigate the effect of elevated CO2 on nutritional physiology of bread wheat (Triticum aestivum) as influenced K and Zn deficiencies, N form and drought stress. It was found that K deficiency severely impeded the positive effects of elevated CO2 on photosynthetic performance and biomass production of well-watered or drought-stressed plants. Plants suffering from K deficiency also accumulated more carbohydrates in source leaves under elevated CO2 and drought stress conditions. In later growth stages, elevated CO2 partly compensated the effect of K deficiency on grain yield through influencing number of spikes and thousand grain weight. Elevated CO2 was also shown to ameliorate adverse effects of Zn deficiency and drought stress on biomass production and grain yield but with a concomitant deterioration of the grain nutritional quality in terms of Zn and protein concentration, particularly in plants with low Zn supply. Concerning N form, elevated CO2 was most effective on NH4NO3 treated plants resulting in the highest biomass enhancement ratio and an optimum N and carbohydrate metabolism. Nevertheless, elevated CO2 caused dilution of most of the mineral nutrients in both foliage and grain, suggesting that a future climate with elevated CO2 may result in serious consequences to human and animal nutrition