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Title: ELEVATED GROWTH CO2 DELAYS DROUGHT STRESS AND ACCELERATES RECOVERY OF RICE LEAF PHOTOSYNTHESIS.

Author
item WIDODO, W. - UNIV. OF FLORIDA
item Vu, Joseph
item BOOTE, KENNETH - UNIV. OF FLORIDA
item BAKER, JEFFREY - USDA, ARS
item Allen Jr, Leon

Submitted to: Environmental and Experimental Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/30/2002
Publication Date: 6/1/2003
Citation: Widodo, W., Vu, J.C.V., Boote, K.J, Baker, J.T., Allen, L.H., 2003 Elevated growth CO2 delays drought stress and accelerates recovery of rice leaf photosynthesis. Environmental and Experimental Botany 49: 259-272

Interpretive Summary: The global atmospheric carbon dioxide (CO2), presently at 375 ppm, is expected to double by the end of this century. Predicted climate changes, including shifts in rainfall patterns, could result in decreased soil moisture in some areas of the world. In this study, by USDA-ARS and University of Florida scientists in Gainesville, FL, rice was grown at ambient or twice-ambient CO2 under continuously flooded conditions or drought stress imposed during the reproductive growth phases. The purposes were to assess the combined effects of high CO2 and drought on rice leaf photosynthesis, and to test if high growth CO2 could alleviate the adverse effects of drought on rice leaf photosynthesis. The results showed that high CO2 enhanced leaf photosynthesis and carbohydrate accumulation, whereas severe drought caused substantial declines in these parameters. The drought-induced effects, however, were more severe for plants grown at ambient than at high CO2. In addition, high CO2 delayed the onset of drought-related changes in leaf photosynthesis, and leaf photosynthesis recovered from drought stress more rapidly in the high CO2 treatment. Thus, rice grown under future increases in atmospheric CO2 was better able to tolerate drought situations

Technical Abstract: Rice (Oryza sativa L. cv. IR-72) was grown season-long in sunlit, controlled-environment chambers at ambient and twice-ambient CO2 under continuous flooding, or drought imposed during panicle initiation and anthesis growth phases. At high CO2, leaf CO2 exchange rate (CER) and content of chlorophyll (Chl) were higher at all sampling dates, whereas total soluble protein (TSP) decreased on several sampling dates, compared to plants at ambient CO2. High CO2 increased leaf sucrose-phosphate synthase (SPS) activity throughout the season, and enhanced leaf sucrose and starch accumulation during early reproductive phases. Near the end of drought periods, severe water deficit caused substantial decreases in CER and concentrations of Chl and TSP, with concomitant reductions in photosynthetic primary products and SPS activity. These drought-induced effects were more severe for plants grown at ambient than at high CO2. Furthermore, plants grown at high CO2 were able to maintain leaf CER, and to some extent other photosynthetic-related parameters, longer into the drought period than plants grown at ambient CO2. In addition, leaf CER recovered from drought more rapidly in the high CO2 treatment. Thus, in the absence of other climate stresses, rice grown under future increases in atmospheric CO2 may be better able to tolerate drought situations.