1a. Objectives (from AD-416):
The objectives of this agreement are to 1) Determine how rising temperature alters responses of crop and weed physiology, growth, and product quality to elevated carbon dioxide; 2) Assess genotype by environment interactions in crop responses to elevated carbon dioxide and temperature, and 3) Determine whether responses to rising atmospheric carbon dioxide and temperature of weeds of the crop systems used in Objectives 1 & 2 will increase their range, competitiveness and resistance to control.
1b. Approach (from AD-416):
Research will focus on determining how rising temperature alters responses of crop and weed physiology, growth, and product quality to elevated carbon dioxide. Differences among genotypes within several crop species in responses to elevated carbon dioxide and temperature will be assessed to identify traits which would help to adapt crops to these global change conditions. Responses of weeds in a locally and nationally important crop system will be evaluated to determine if rising atmospheric carbon dioxide and temperature will increase their impact on crop yields and their resistance to control by glyphosate, a popular herbicide. Work will be conducted in controlled environment chambers and in field plots with open top chambers and with a free air carbon dioxide enrichment system.
3. Progress Report:
Elevated carbon dioxide concentrations have been found to protect photosynthesis and plant growth from reductions caused by moderately dry soil in cotton plants, but did not protect soybean plants from the same soil water stress. This difference in plant response to soil water stress at elevated carbon dioxide was the result of species differences in the response of plant hydraulic conductance to growth at elevated carbon dioxide, with hydraulic conductance unaffected by growth at elevated carbon dioxide in cotton, but decreased in soybean. In corn, it was found that elevated carbon dioxide concentrations slowed the development of plant water deficits during drought, and that this resulted in distinctive patterns of changes in plant biochemical components in the early stages of drought. Responses of transgenic corn lines differing in drought tolerance were examined for responses to drought and carbon dioxide concentration to identify biochemical characteristics related to differences in drought tolerance. Growth of weedy red rice at elevated carbon dioxide changed its growth rate and flowering time such that there was more gene exchange with an herbicide-resistant cultivated variety of rice. This could allow more rapid development of herbicide resistance in weedy red rice as the atmospheric carbon dioxide concentration rises.
1. A new method of applying a controlled soil water stress. Drought is projected to have an increasing impact on crop production in the U.S. A new method of applying a controlled soil water stress was developed by ARS researchers in Beltsville, Maryland. With this method the soil water stress achieved is independent of plant transpiration rate. This method could greatly facilitate the screening of crop lines for drought tolerance, in order to improve their adaptation to drought.
Ziska, L.H. 2011. Climate change, carbon dioxide and global crop production: Food security and uncertainty. In: Dinar, A., Mendelsohn, R., editors. Handbook on Climate Change and Agriculture. Cheltenham, United Kingdom: Edward Elgar Publishing. p. 9-31.