PLANT PHYSIOLOGY , Vol 103, Issue 3 741-752, Copyright © 1993 by American Society of Plant Biologists

ENVIRONMENTAL AND STRESS PHYSIOLOGY

The Role of Flavonol Glycosides and Carotenoids in Protecting Soybean from Ultraviolet-B Damage

E. M. Middleton and A. H. Teramura
Laboratory for Terrestrial Physics, National Aeronautics and Space Administration/Goddard Space Flight Center, Greenbelt, Maryland 20771 (E.M.M.)

The increase in ultraviolet-B (UV-B; 0.290-0.320 [mu]m) radiation received by plants due to stratospheric ozone depletion heightens the importance of understanding UV-B tolerance. Photosynthetic tissue is believed to be protected from UV-B radiation by UV-B-absorbing compounds (e.g. flavonoids). Although synthesis of flavonoids is induced by UV-B radiation, its protective role on photosynthetic pigments has not been clearly demonstrated. This results in part from the design of UV-B experiments in which experimental UV-A irradiance has not been carefully controlled, since blue/UV-A radiation is involved in the biosynthesis of the photosynthetic pigments. The relationship of flavonoids to photosynthetic performance, photosynthetic pigments, and growth measures was examined in an experiment where UV-A control groups were included at two biologically effective daily UV-B irradiances, 14.1 and 10.7 kJ m-2. Normal, chlorophyll-deficient, and flavonoid-deficient pigment isolines of two soybean (Glycine max) cultivars that produced different flavonol glycosides (Harosoy produced kaempferol, Clark produced quercetin and kaempferol) were examined. Plants with higher levels of total flavonoids, not specific flavonol glycosides, were more UV-B tolerant as determined by growth, pigment, and gas-exchange variables. Regression analyses indicated no direct relationship between photosynthesis and leaf levels of UV-B-absorbing compounds. UV-B radiation increased photosynthetic pigment content, along with UV-B-absorbing compounds, but only the former (especially carotenoids) was related to total biomass (r2 = 0.61, linear) and to photosynthetic efficiency (negative, exponential relationship, r2 = 0.82). A reduction in photosynthesis was associated primarily with a stomatal limitation rather than photosystem II damage. This study suggests that both carotenoids and flavonoids may be involved in plant UV-B photoprotection, but only carotenoids are directly linked to photoprotection of photosynthetic function. These results additionally show the importance of UV-A control in UV-B experiments conducted using artificial lamps and filters.

This article has been cited by other articles:

				S. Czemmel, R. Stracke, B. Weisshaar, N. Cordon, N. N. Harris, A. R. Walker, S. P. Robinson, and J. Bogs The Grapevine R2R3-MYB Transcription Factor VvMYBF1 Regulates Flavonol Synthesis in Developing Grape Berries Plant Physiology, November 1, 2009; 151(3): 1513 - 1530. [Abstract] [Full Text] [PDF]

				I. A. M. Yunusa, M. D. Burchett, V. Manoharan, D. L. DeSilva, D. Eamus, and C. G. Skilbeck Photosynthetic Pigment Concentrations, Gas Exchange and Vegetative Growth for Selected Monocots and Dicots Treated with Two Contrasting Coal Fly Ashes J. Environ. Qual., July 1, 2009; 38(4): 1466 - 1472. [Abstract] [Full Text] [PDF]

				N. W. Albert, D. H. Lewis, H. Zhang, L. J. Irving, P. E. Jameson, and K. M. Davies Light-induced vegetative anthocyanin pigmentation in Petunia J. Exp. Bot., May 1, 2009; 60(7): 2191 - 2202. [Abstract] [Full Text] [PDF]

				P. K. E. Campbell, E. M. Middleton, J. E. McMurtrey, L. A. Corp, and E. W. Chappelle Assessment of Vegetation Stress Using Reflectance or Fluorescence Measurements J. Environ. Qual., May 7, 2007; 36(3): 832 - 845. [Abstract] [Full Text] [PDF]

				F. M. Frey Phenotypic integration and the potential for independent color evolution in a polymorphic spring ephemeral Am. J. Botany, March 1, 2007; 94(3): 437 - 444. [Abstract] [Full Text] [PDF]

				P. Dixon, C. Weinig, and J. Schmitt Susceptibility to UV damage in Impatiens capensis (Balsaminaceae): testing for opportunity costs to shade-avoidance and population differentiation Am. J. Botany, August 1, 2001; 88(8): 1401 - 1408. [Full Text]

				L. C. Olsson, L. Fraysse, and J. F. Bornman Influence of high light and UV-B radiation on photosynthesis and D1 turnover in atrazine-tolerant and -sensitive cultivars of Brassica napus J. Exp. Bot., February 2, 2000; 51(343): 265 - 274. [Abstract] [Full Text] [PDF]

				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]

				T. Götz, U. Windhövel, P. Böger, and G. Sandmann Protection of Photosynthesis against Ultraviolet-B Radiation by Carotenoids in Transformants of the Cyanobacterium Synechococcus PCC7942 Plant Physiology, June 1, 1999; 120(2): 599 - 604. [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]