TITLE:
Effect of Ambient UV-B on Stomatal Density, Conductance and Isotope Discrimination in Four Field Grown Soybean [Glycine max (L.) Merr.] Isolines
AUTHORS:
Dennis C. Gitz III, Steven J. Britz, Joseph H. Sullivan
KEYWORDS:
Soybean; UV-B; Drought Stress; Water Use Efficiency; Isotope Discrimination; Photomorphogenesis
JOURNAL NAME:
American Journal of Plant Sciences,
Vol.4 No.12C,
December
25,
2013
ABSTRACT: An experiment was designed to test whether ambient levels of UV-B radiation affect stomatal development, decrease stomatal density, and lead to increased water-use efficiency (WUE). Soybean [Glycine max (L.) Merr.] isolines with different stomatal distribution and flavonol expression patterns were field grown under shelters that either transmitted or blocked solar UV-B. All isolines exposed to solar UV-B accumulated higher concentrations of UV-screening phenolic pigments but other responses were isoline dependent. Solar UV-B decreased stomatal density and conductance in isolines expressing a unique branched kaempferol triglycoside. Decreased stomatal density was associated with increased season-long WUE and decreased internal CO2 concentration of leaf (estimated by δ13C discrimination). We concluded that photomorphogenic responses to UV-B affected stomatal density and WUE in field grown soybean; but that the magnitude and direction of these response were associated with isogenic pleiotropic differences in stomatal distribution and pigment expression. UV-B radiation had no effect on biomass accumulation or yield in a cultivar expressing only trace levels of kaempferol suggesting that flavonol expression is not prerequisite to UV-B tolerance.