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United States Department of Agriculture

Agricultural Research Service

Research Project: CROP AND WEED RESPONSES TO INCREASING ATMOSPHERIC CARBON DIOXIDE
2010 Annual Report


1a.Objectives (from AD-416)
Determine relationships between effects of elevated carbon dioxide on gene expression and physiological responses which increase the response of crop yield to atmospheric and climatic global changes. Determine how changes in carbon dioxide concentration affect the relative competitiveness of crops and weeds. Determine how elevated carbon dioxide affects relationships between fertilizer and weed management practices and crop yield and soil carbon sequestration.


1b.Approach (from AD-416)
Crop and weed species will be grown at the current ambient concentration of carbon dioxide and at 1.5 times that concentration in field plots, using open top chambers, and in growth cabinets. Changes in gene expression, physiology, and the growth of crops will examined at ambient and elevated concentrations of carbon dioxide in combination with high temperature stress, drought stress, and competition from weeds. Soybeans, common beans, spring wheat, oats and some weed species will be examined for genotypic differences in responsiveness to carbon dioxide concentration. Invasive and non-invasive weed species will be compared for responses to rising atmospheric carbon dioxide. Impacts of elevated carbon dioxide on yield responses to nitrogen fertilizer will be determined in a corn, wheat, soybean crop rotation system. The effect of elevated carbon dioxide on soil carbon sequestration will be examined in two no-till cropping systems.


3.Progress Report
This project ended and was replaced by project 1265-11210-008-00D "Response and adaptation of crops and weeds to elevated C02 and global warming." Over the five years of this project, we identified many genes in corn and Arabidopsis whose expression was increased or decreased several fold as a result of exposure to elevated CO2. Because so many different genes in so many different metabolic pathways were affected, this information is as yet difficult to interpret. However, changes in the nitrogen metabolism pathway caused by elevated CO2, which resulted in nitrogen deficiency symptoms, were documented in multiple species. In the next project, more attention will be focused on a narrower group of genes known to be related to high and low temperature stress tolerance, to determine the effect of CO2 on their expression in relation to changes in plant tolerance to those stresses. In the project which ended, we identified varieties and traits in both common beans and soybeans, which are candidates for improving the adaptation of these crops to elevated carbon dioxide itself, and also to the combination of elevated carbon dioxide with high temperature and drought stresses. The next project will test the usefulness of some specific adaptive traits in both of these species, based on knowledge developed in the prior project. The completed project found that the response of field-grown maize to fertilizer nitrogen differed significantly with carbon dioxide concentration, with crops grown at elevated carbon dioxide requiring more nitrogen. No significant effects of elevated CO2 or nitrogen fertilizer application on soil carbon content occurred over the 5 years of this project. It was found that no-till management by itself did not result in any changes in soil carbon sequestration at any nitrogen fertility level over five years. These treatments will be continued in the new project. An increase in the competitiveness of weeds towards crops at elevated CO2, and a decrease in the effectiveness of glyphosate in preventing multiple species of weeds from reducing crop yields at elevated carbon dioxide were documented in the prior plan. This work will continue in the new plan. A new method was developed for partitioning the limitations to photosynthesis in C3 species, which will aid in understanding the nature of the limitations to plant growth as CO2 changes.


4.Accomplishments
1. Rising atmospheric CO2 favors weedy rice over cultivated rice. Rising atmospheric CO2 increases the growth of many crops, but also the growth of weeds. Weedy red rice is a troublesome weed in cultivated rice fields. These experiments showed that the growth of the weed increased more with CO2 than rice, and that in the competition between the weedy and cultivated rice, higher CO2 favored the weedy rice, to the detriment of rice yield. These results indicate that rising atmospheric CO2 could decrease rice yields unless the control of weedy red rice is improved.


Review Publications
Sicher Jr, R.C., Bunce, J.A., Matthews, B.F. 2010. Differing responses to carbon dioxide enrichment by a dwarf and a normal-sized soybean cultivar may depend on sink capacity. Canadian Journal of Plant Science. 90:257-264.

Bunce, J.A. 2009. Use of the response of photosynthesis to oxygen to estimate mesophyll conductance to carbon dioxide in water-stressed soybean leaves. Plant Cell and Environment. 32:875-881.

Sicher Jr, R.C., Bunce, J.A. 2008. Growth, photosynthesis, nitrogen partitioning and responses to CO2 enrichment in barley mutants lacking NADH-dependent nitrate reductase activity. Physiologia Plantarum. 134:31-40.

Ziska, L.H., Runion, G.B., Tomecek, M.B., Prior, S.A., Torbert III, H.A., Sicher Jr., R.C. 2009. An evaluation of cassava, sweet potato and field corn as potential carbohydrate sources for bioethanol production in Alabama and Maryland. Biomass and Bioenergy. 33:1503-1508.

Bradley, B.A., Blumenthal, D.M., Wilcove, D.S., Ziska, L.H. 2009. Predicting plant invasion in an era of global change. Trends in Ecology and Evolution. 25:310-318.

Ziska, L.H., Tomecek, M.B., Gealy, D.R. 2010. Competitive interactions between cultivated and red rice as a function of recent and projected increases in atmospheric carbon dioxide. Agronomy Journal. 102:118-123.

Ziska, L.H., Epstein, P.R., Schlesinger, W. 2009. Rising CO2, climate change, and public health: Exploring the links to plant biology. Environmental Health Perspectives. 117(2):155-158.

Last Modified: 9/1/2014
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