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Title: Utraviolet-B effects on stomatal density, water use efficiency, and stable carbon isotope discrimination in four glasshouse-grown soybean cultivars

Author
item Gitz, Dennis
item Britz, Steven
item SULLIVAN, JOE - NRSL UNVI. OF MARYLAND
item Liu Gitz, Lan

Submitted to: Environmental and Experimental Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/19/2004
Publication Date: 6/1/2005
Citation: Gitz, D.C., Britz, S.J., Sullivan, J., Liu Gitz, L. 2005. Utraviolet-B effects on stomatal density, water use efficiency, and stable carbon isotope discrimination in four glasshouse-grown soybean cultivars. Environmental and Experimental Botany. 53(3):343-355.

Interpretive Summary: Interactions between UV-B radiation and drought stress have been observed but the underlying mechanisms have not been thoroughly investigated. We hypothesized that UV-B radiation would improve water use efficiency by its effects on epidermal development, specifically stomatal density and leaf gas exchange. Soybean plants were grown in a greenhouse with and without simulated solar UV-B from sunlamps. UV-B induced formation of phenols such as "flavonoids" which are thought to act as UV screening compounds. UV-B reduced the numbers of stomata, pores which regulate water use, on the leaves. As a result, water use was reduced by UV radiation. UV-B exerts an influence on soybean development that results in improved water use efficiency and could improve drought tolerance in some cultivars.

Technical Abstract: Interactions between UV-B radiation and drought stress have been observed but the underlying mechanisms have not been thoroughly investigated. We hypothesized that UV-B radiation would improve water use efficiency by its effects on epidermal development, specifically stomatal density and leaf gas exchange. Soybean (Glycine max L. cultivars Essex, Williams, OX921 and OX922) plants were grown for 28 d in a glasshouse with and without supplemental UV-B radiation levels of 13 kJ m-2 biologically effective radiation. UV-B radiation increased phenolic content of leaves but reduced leaf area. Adaxial stomatal density was reduced in all cultivars but abaxial stomatal density was only reduced in the OX922 cultivar. Stomatal conductance was reduced in concert with stomatal density as was internal CO2 concentration (Ci). Instantaneous water use efficiency was increased in Essex, Williams and OX922 and stable carbon isotope analysis showed similar trends in long-term water use efficiency. These results are consistent with the notion that UV-B exerts a photomorphogenic influence on soybean development that results in improved water use efficiency and could improve drought tolerance in some cultivars.