||Effects of Ultraviolet-B Irradiation on Plants during Mild Water Stress. 1. Effects on Diurnal Stomatal Resistance.
Teramura, A. H. ;
Tevini, M. ;
Iwanzik, W. ;
||Maryland Univ., College Park. Dept. of Botany.;Corvallis Environmental Research Lab., OR.
||CONTRIB-6349; EPA-R-808035; EPA-600/J-83-037;
Radiation effects ;
Cucumis sativus ;
Raphanus sativus ;
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Cucumber (Cucumis sativus L. cv. Delikatess) and radish (Raphanus sativus L. cv. Saxa Treib) were grown in a factorial design under two ultraviolet-B (UV-B) irradiances and three levels of water stress. On a weighted, daily dose basis the UV-B radiation treatments were equivalent to ambient levels during the beginning of the growing season (controls) and those predicted for an 11.6% ozone depletion during the summer solstice at 49 deg. N latitude. Water stress was achieved by varying the frequency of watering. The combination of UV-B radiation and water stress resulted in large species differences in the pattern of stomatal resistances. This study indicated that Cucumis is one of the most sensitive crop species to UV-B radiation yet identified and that the primary effect of UV-B radiation in this species is a decrease in the leaf diffusive resistance to water vapor. This, therefore, may result in reductions in growth via increased water stress.