This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via CrossRef Citing Articles via Web of Science (80) Citing Articles via Google Scholar Google Scholar Articles by Ziska, L. H. Articles by Teramura, A. H. Search for Related Content PubMed PubMed Citation Articles by Ziska, L. H. Articles by Teramura, A. H. Agricola Articles by Ziska, L. H. Articles by Teramura, A. H.

Environmental and Stress Physiology

CO₂ Enhancement of Growth and Photosynthesis in Rice (Oryza sativa) ¹

Modification by Increased Ultraviolet-B Radiation

Department of Botany, University of Maryland, College Park, Maryland 20742

Two cultivars of rice (Oryza sativa L.) IR-36 and Fujiyama-5 were grown at ambient (360 microbars) and elevated CO₂ (660 microbars) from germination through reproduction in unshaded greenhouses at the Duke University Phytotron. Growth at elevated CO₂ resulted in significant decreases in nighttime respiration and increases in photosynthesis, total biomass, and yield for both cultivars. However, in plants exposed to simultaneous increases in CO₂ and ultraviolet-B (UV-B) radiation, CO₂ enhancement effects on respiration, photosynthesis, and biomass were eliminated in IR-36 and significantly reduced in Fujiyama-5. UV-B radiation simulated a 25% depletion in stratospheric ozone at Durham, North Carolina. Analysis of the response of CO₂ uptake to internal CO₂ concentration at light saturation suggested that, for IR-36, the predominant limitation to photosynthesis with increased UV-B radiation was the capacity for regeneration of ribulose bisphosphate (RuBP), whereas for Fujiyama-5 the primary photosynthetic decrease appeared to be related to a decline in apparent carboxylation efficiency. Changes in the RuBP regeneration limitation in IR-36 were consistent with damage to the photochemical efficiency of photosystem II as estimated from the ratio of variable to maximum chlorophyll fluorescence. Little change in RuBP regeneration and photochemistry was evident in cultivar Fujiyama-5, however. The degree of sensitivity of photochemical reactions with increased UV-B radiation appeared to be related to leaf production of UV-B-absorbing compounds. Fujiyama-5 had a higher concentration of these compounds than IR-36 in all environments, and the production of these compounds in Fujiyama-5 was stimulated by UV-B fluence. Results from this study suggest that in rice alterations in growth or photosynthesis as a result of enhanced CO₂ may be eliminated or reduced if UV-B radiation continues to increase.

¹ This work was supported in part by the U.S. Environmental Protection Agency's Environmental Research Laboratory in Corvallis, OR (CR 814017-02-0). Scientific Article No. A 6326, Contribution No. 8502, of the Maryland Agriculture Experiment Station. Although the work described herein was funded in part by the U.S. Environmental Protection Agency, it has not been subjected to the agency's peer review and therefore does not necessarily reflect the views of the agency and no official endorsement should be inferred.

This article has been cited by other articles:

				S. Nogués, D. J. Allen, J. I.L. Morison, and N. R. Baker Characterization of Stomatal Closure Caused by Ultraviolet-B Radiation Plant Physiology, October 1, 1999; 121(2): 489 - 496. [Abstract] [Full Text]

				S. Nogués, D. J. Allen, J. I.L. Morison, and N. R. Baker Ultraviolet-B Radiation Effects on Water Relations, Leaf Development, and Photosynthesis in Droughted Pea Plants Plant Physiology, May 1, 1998; 117(1): 173 - 181. [Abstract] [Full Text]