Interaction of Elevated Ultraviolet-B Radiation and CO₂ on Productivity and Photosynthetic Characteristics in Wheat, Rice, and Soybean

Abstract

Wheat (Triticum aestivum L. cv Bannock), rice (Oryza sativa L.cv , and soybean (Glycine max [L.] Merr cv Essex) were grown in a factorial greenhouse experiment to determine if C02-induced increases in photosynthesis, biomass, and yield are modified by increases in ultraviolet (UV)-B radiation corresponding to stratospheric ozone depletion. The experimental conditions simulated were: (a) an increase in CO2 concentration from 350 to 650 microliters per liter; (b) an increase in UV-B radiation corresponding to a 10% ozone depletion at the equator; and (c) a and b in combination. Seed yield and total biomass increased significantly with elevated CO2 in all three species when compared to the control. However, with concurrent increases in UV-B and CO2, no increase in either seed yield (wheat and rice) or total biomass (rice) was observed with respect to the control. In contrast, CO2-induced increases in seed yield and total plant biomass were maintained or increased in soybean within the elevated C02, UV-B environment. Whole leaf gas exchange indicated a significant increase in photosynthesis, apparent quantum efficiency (AQE) and water-use-efficiency (WUE) with elevated CO2 in all 3 species. Including elevated UV-B radiation with high CO2 eliminated the effect of high CO2 on photosynthesis and WUE in rice and the increase in AQE associated with high CO2 in all species. Elevated CO2 did not change the apparent carboxylation efficiency (ACE) in the three species although the combination of elevated CO2 and UV-B reduced ACE in wheat and rice. The results of this experiment illustrate that increased UV-B radiation may modify C02-induced increases in biomass, seed yield and photosynthetic parameters and suggest that available data may not adequately characterize the potential effect of future, simultaneous changes in CO2 concentration and UV-B radiation.Current atmospheric levels of CO2 may double from 340 ,uL L-' to 680 ,uL L`by the middle of the 21st century (8).It is evident from a number of field and greenhouse experiments that increases in CO2 will have a significant effect on layer with subsequent increases in the amount of solar ultra- ( 17). In addition to CO2, other trace gases are also increasing as a result of industrialization. The rise of chlorofluorocarbons (CFCs), methane (CH4), and nitrous oxide (N20) may substantially deplete the stratospheric ozone violet-B radiation (UV-B, between 290-320 nm) reaching the earth's surface (1,3). Although this predicted increase is small relative to the entire electromagnetic spectrum, UV-B has a disproportionately large photobiological effect due to its absorption by proteins and nucleic acids. In UV-B sensitive plants, photosynthetic capacity may be reduced directly by the effect of UV-B radiation on photosynthetic enzymes or disruption of PSII reaction centers, or indirectly by effects on photosynthetic pigments and stomatal function (9,13,19,20).Both CO2 and UV-B radiation are expected to increase simultaneously with future changes in global climate. To date...

Cotton responses to ultraviolet-B radiation: experimentation and algorithm development

“…2C), it is concluded that higher UV-B radiation (16 kJ m −2 per day) has both direct and indirect effects on cotton leaf photosynthesis. Similar reductions in photosynthesis were observed in other crop species such as soybean (Vu et al, 1981) and rice (Teramura et al, 1990). Nogues et al (1999) also reached a similar conclusion that there is a direct effect of UV-B radiation on stomatal conductance in addition to that caused by changes in mesophyll photosynthesis of pea, Asiatic dayflower (Commelina communis L.), and oilseed rape (Brassica napus L.) plants.…”

“…In addition to the intensive investigations on growth and physiological responses to UV-B radiation on many field crops such as bean (Phaseolus vulgaris L.) (Deckmyn et al, 1994), maize (Zea mays L.) (Correia et al, 1998(Correia et al, , 1999Mark and Tevini, 1996), pea (Pisum sativum L.) (Day et al, 1996;Mepsted et al, 1996), rice (Oryza sativa L.) (Dai et al, 1992;Teramura et al, 1990), soybean [Glycine max (L.) Merr.] (Miller et al, 1994;Sinclair et al, 1990;Teramura et al, 1990), sunflower (Helianthus annuus L.) (Battaglia and Brennen, 2000), and wheat (Triticum aestivum L.) (Li et al, 2000;Teramura et al, 1990), several reviews have recently summarized the effects and consequences of UV-B radiation on major agricultural and horticultural crops, and nonagricultural species (Allen, 1990(Allen, , 1994Allen et al, 1998;Caldwell et al, 1998;Groth and Krupa, 2000;Krupa and Kickert, 1989;Teramura and Sullivan, 1994). The inferences from these studies and reviews are that plant sensitivities to UV-B radiation differ among species and cultivars within a species; however, little is known about the responses of cotton (Gossypium hirsutum L.), a major economic crop grown on over 32 Mha worldwide and over 5 Mha in the United States (http://www.ers.usda.gov/briefing/cotton).…”

Impact of enhanced ultraviolet-B irradiance on cotton growth, development, yield, and qualities under field conditions

“…One-third to one-half of all plant species tested are deleteriously affected by UV-B levels "above ambient" (Sullivan, 1992). A substantial number of studies have been conducted that have evaluated the potential consequences of an increase in UV-B radiation on many plants (Tevini et al, 1981;Teramura et al, 1990;Miller et al, 1994;Caldwell et al, 1998;Correia et al, 1998Correia et al, , 1999Li et al, 2000, Searles et al, 2001), but we have a rather limited understanding of the role that UV-B radiation plays in controlling cotton growth, development, yield and quality. Searles et al (2001) searched for "all suitable published studies" with field-based measurements of UV-B influences on vascular plants and found no studies on cotton.…”

Utility of basic research in plant/crop physiology in relation to crop improvement: a review and a personal account

“…Moreover, global climate changes that might negatively affect agricultural M.A. El-Sharkawy productivity in many parts of the world would further aggravate deficits in future food supply (Quebedeaux, 1990;Teramura, 1990;Teramura et al, 1990;Titus, 1990;Wittwer, 1990;Rosenzweig and Parry, 1994). Rosenzweig and Parry (1994), in assessing the effects of climate changes on cereal production, found that it will increase the current disparities between developed and developing countries.…”

“…But it is necessary here to point out a few of the many positive achievements and contributions of basic research in the fields of plant and crop physiology that have been translated so far into gains in agricultural productivity through plant breeding and management of cropping ecosystems. Furthermore, in view of the increasingly changing global climate, the role of plant and crop physiological research in characterizing and predicting responses of a given plant and crop species as well as natural and agricultural ecosystems performances under these dynamically changing environmental conditions will be even greater (Hesketh et al, 1984;Begonia et al,1987Begonia et al, ,1996Begonia et al, ,1999Bazzaz, 1990;Besford et al, 1990;Teramura et al, 1990;Idso et al, 1991;Ziska et al, 1991;Acock and Acock, 1993;Chen et al, 1993, Gifford andMorison, 1993;Hall and Allen, 1993;Patterson, 1993;Sinha, 1993;Rosenzweig, 1993;Rosenzweig and Parry;Bunce and Sicher, 2004;Sholtis et al, 2004;Long et al, 2006).…”