1a. Objectives (from AD-416):
The objectives of this project 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:
Tests continue comparing the response of twelve cultivars of rice to the combination of high temperature stress and elevated carbon dioxide concentration, as a step in the identification of genes adapting rice to future climatic conditions. The impact of elevated carbon dioxide concentrations on the reduction in yield of soybeans caused by the weed velvetleaf were determined in field experiments, to determine whether impacts of weeds on crop yields may increase as the atmospheric carbon dioxide concentration rises. Similar experiments were conducted with tomato as the crop, and pigweed as the weed species. In corn, we determined that tests to identify cultivars with exceptionally high efficiency of water use at future atmospheric carbon dioxide levels need to be conducted at those higher carbon dioxide concentrations, because cultivar rankings in this trait vary with carbon dioxide concentration. We determined that in experiments at elevated concentrations of carbon dioxide, the degree of short-term variation in carbon dioxide concentration occurring in a particular experimental system can have a large impact on the plant response, although information on short-term variation is seldom reported. We determined that in corn, damage to photosynthesis caused by a brief high temperature stress was greater at elevated carbon dioxide than at the current ambient carbon dioxide concentration when leaf temperature was carefully controlled, but that the relative ranking of the heat tolerance of two cultivars was not affected by growth at elevated carbon dioxide concentrations.
1. Elevated carbon dioxide mitigates high temperature stress. Global climate change is expected to increase ambient temperatures in most important crop growing areas of the world. In this study we examined the combined effects of carbon dioxide enrichment and increased growth temperatures on soybean metabolism. Several critical organic acids involved in respiratory metabolism were decreased by 50 to 95% when soybean plants were grown under ambient carbon dioxide concentrations and with elevated growth temperatures. These temperature dependent changes of organic acids were almost completely reversed by carbon dioxide enrichment. These findings suggested that a major site of carbon dioxide mitigation of temperature stress in soybean involves respiratory organic acid metabolism.
2. Development of crops adapted to climate change. In spite of the recognition that atmospheric carbon dioxide is an essential plant resource that has increased globally by about 25% since 1970, efforts to increase the biological conversion of atmospheric carbon dioxide concentration to increase agricultural seed yield through crop selection is not generally recognized as an effective adaptation measure. In this analysis, we challenge that viewpoint through an assessment of existing studies on carbon dioxide concentration and intraspecific variability. We illustrate the potential biological basis for differential plant response among crop lines. We also demonstrate that while technical hurdles remain, active selection and breeding for carbon dioxide responsiveness among cereal varieties may provide one of the simplest and direct strategies to increase global yields and maintain food security with anthropogenic change.Zhu, C., Ziska, L.H., Sakai, H., Zhu, J., Hasegawa, T. 2013. Vulnerability of lodging risk to elevated CO2 and increased soil temperature differs between rice cultivars. European Journal of Agronomy. 46:20-24.