|Allen, Leon - Hartwell|
Submitted to: Current Topics in Plant Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/23/2007
Publication Date: 5/17/2007
Citation: Vu, J.C., Allen Jr, L.H., Widodo, W. 2007. Leaf photosynthesis and Rubisco activity and kinetics of soybean, peanut, and rice grown under elevated atmospheric CO2, supraoptimal air temperature, and soil water deficit.Current Topics in Plant Biology. 7:27-41. Interpretive Summary: Atmospheric carbon dioxide (CO2) level is expected to double within this century. Consequently, increases in air temperature (T) by as much as 4-6C and shifts in rainfall patterns that could reduce soil moisture in some parts of the world have been predicted. There are few studies addressing the interactive effects of high CO2-high T, or high CO2-drought, on plant photosynthesis (PS). PS is a process by which leaves absorb air CO2 to make products required for plant growth. In this study, by scientists at the USDA-ARS and University of Florida in Gainesville, FL, soybean, peanut and rice were grown at ambient or twice-ambient CO2, and under daytime T from 28 to 48C or soil water deficit. The results indicate that leaf PS of the test plants was enhanced by high CO2, but decreased by high T and drought. For soybean, high-CO2 plants compensated much better for the adverse effects of high T on PS. For rice, high CO2 delayed the substantial reduction in PS by severe drought. High CO2, high T and drought also reduced the activity of Rubisco, an important but inefficient PS protein for the majority of vegetation, including the test plants. The results suggest that many generations of growth at high CO2 might be required for Rubisco of such crop plants to evolve towards a more effective type protein.
Technical Abstract: Soybean, peanut and rice were grown at 350 and 700 (high) ppm CO2, and under varying day/night temperature (T) regimes ranging from 28/18 to 48/38C for soybean and peanut, or soil water deficit for rice, (a) to determine the interactive impacts of high CO2-high T, or high CO2-drought, on midday leaf CO2 exchange rate (CER) and Rubisco activity, and (b) to test whether high CO2, high T or drought stress would induce changes in the Rubisco Km(CO2). CER of soybean, peanut and rice was increased by high CO2, but decreased by high T and drought. For soybean, the high-CO2 plants compensated much better for the adverse effects of high T on CER. For the drought-imposed rice plants, high CO2 delayed by one day the substantial reduction in CER. High CO2, high T and severe drought also reduced Rubisco initial and total activities and activation state. Soybean and peanut Rubisco initial Km(CO2) was not altered by high CO2 or high T, as neither severe drought changed the rice Rubisco initial Km(CO2), but there were moderate increases in Rubisco total Km(CO2) for soybean and peanut at high CO2 and high T. The results suggest that multiple generations of growth at high CO2 might be required for Rubisco of C3 plants to evolve towards a more effective type enzyme.