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
Effects of long-term and short-term elevation of carbon dioxide concentration on the tolerance of photosynthesis to high and low temperatures were examined in controlled environment chambers in maize, soybean, and common bean. No protective effect of elevated CO2 was observed in any case. Consistent with our prior work, elevated CO2 delayed responses of maize to drought, and we further observed qualitative differences in metabolic clusters between ambient and elevated CO2 treatments. We are using drought tolerant and drought sensitive hybrid lines to investigate whether the CO2 effect on the plant responses to drought is more than just to delay drought. Variation was found in the ability of rice and common bean varieties to produce seed at high temperatures and elevated carbon dioxide concentrations, in experiments in controlled environment chambers. Leaf water use efficiency of four maize genotypes was compared under field conditions at elevated carbon dioxide, using the new free air carbon dioxide enrichment system. Competition between soybeans and velvetleaf at ambient and elevated carbon dioxide concentrations was examined under field conditions. Modeling work indicated that changes in temperature may alter the principle agronomic weeds in corn and soybean growing areas, and increase the range of invasive weed species in the western United States. We found that the duration of the ragweed pollen season has increased by as much as 13–27 days since 1995 primarily due to a delay in the first frost of the fall season.
1. Corn with high water use efficiency identified. With projected warming and increased frequency of drought, and a scarcity of water for irrigation, development of crop varieties which use water more efficiently would aid in maintaining food production in the face of climate change. ARS researchers at Beltsville, Maryland have identified lines of both field corn and sweet corn which use less water for the amount of plant growth accomplished than the standard commercial varieties. This work provides crop breeders with genetic resources to use to improve the efficiency of water use of corn varieties.