Response of Soybean and Cotton to Climate Change Factors - Carbon Dioxide, Temperature and Water.

Crops will be experiencing increased atmospheric carbon dioxide, temperature and water deficits in future climates. Although independent impacts of these three environmental factors are well understood, the interaction of these factors on crop development, growth and yield are limited and needs further investigation. In this presentation we will summarize the available literature on the interactions of carbon dioxide, temperature and/or water on soybean and cotton. Some data-sets are available from controlled environments on interaction of two factors particularly on  elevated carbon dioxide with temperature or water; and limited information on interaction of temperature and water. There are no detailed data-sets on interaction of all three factors.  Above optimum temperatures had negative influence of growth, yield and quality under ambient or elevated carbon dioxide conditions. Under optimum temperature and moisture conditions, elevated carbon dioxide increased photosynthesis, growth and yield. At above optimum temperatures, the beneficial effects of elevated carbon dioxide on photosynthesis and growth of soybean were more than offset by the negative effects of above optimum temperature on reproductive processes, seed-set, seed numbers, seed-size leading to lower seed yield and poor seed quality. Similar responses were also observed in cotton, where in addition to yield components, the quality of fiber was also negatively influenced by above optimum temperatures at both ambient and elevated carbon dioxide. There were interactions between elevated carbon dioxide and water stress. Elevated carbon dioxide did not off-set the negative effects of water stress on seed yield and quality. Understanding the interaction of temperature and water stress is critical, as these two factors occur commonly under field conditions. However, the interaction effects of temperature and drought are not well quantified. Drought stress can significantly increase canopy temperatures due to partial closure of stomata, resulting in more severe damage under above optimum temperatures. More critical and detailed  research is needed to better understand and quantify the interactive effects of carbon dioxide, temperature and water on crop development, and various physiological and yield traits. Quantitative data on such responses will help us to develop suitable genetic and agronomic management options to minimize the impact of climate change factors on crop productivity. In addition, such data will help develop and improve crop simulation models, so that improved models can be effectively used to make regional and global assessments on impacts of climate change on crop productivity and evaluate available genetic and crop management options.