Sensitivity of Selected Vegetable and Weed Seedlings to Ultraviolet-B Radiation

Abstract

Relative sensitivity of selected vegetable and weed seedlings to ultraviolet-B (UV-B) radiation (280–320 nm) was investigated. Seedlings were grown for 4 weeks in a greenhouse, in chambers equipped with UV-B-emitting fluorescent tubes and Mylar (control) and cellulose acetate (UV-B) filters. UV-B radiation reduced seedling height, leaf area, and leaf fresh weight in tomato (Lycopersicon esculentum `Cour Di Bue'), broccoli (Brassica oleracea var. Italica `Purple Sprouting'), cabbage (Brassica oleracea var. Capitata `Red Drumhead'), and cucumber (Cucumis sativus `Straight Eight'), leaf area and leaf fresh weight in beet (Beta vulgaris `Cylindra' and `Early Wonder'), seedling height and leaf area in spinach (Spinacia oleracea `Long Standing Bloomsdale'), lettuce (Lactuca sativa ``Red Salad Bowl Everest') and `Savoy' cabbage, and seedling height in `Chinese Tip Top' cabbage and lettuce (`Saladin'). `Winterton' cabbage was not affected. UV-B radiation decreased leaf area and leaf fresh weight in common chickweed (Stellaria media) and corn spurry (Spergula arvensis) and seedling height in green foxtail (Setaria viridis) and redroot pigweed (Amaranthus retroflexus). Tillering was stimulated in response to UV-B in green foxtail. There was no effect of UV-B on lady's-thumb (Polygonum persicaria) growth. Leaf number was not affected by exposure to UV-B in any species. The differential morphological sensitivity of vegetable and weed seedlings may result in altered competitive relationships under enhanced UV-B levels expected with the depletion of the earth's ozone layer.