Resumen de Photosensitivity of Cucumber (Cucumis sativus L.) Seedlings Exposed to Ultraviolet-B Radiation

María Luisa Tapia, Guillermo Toro A, Bélgica Parra R, Alejandro Riquelme

• The intensity of ultraviolet-B radiation (UV-B) has increased on the Earth�Ls surface due to the stratospheric ozone depletion, causing an adverse effect on a wide range of species, such as morphological, physiological, and biochemical alterations. This research studied the intraspecific photosensitivity of cucumber (Cucumis sativus L.) seedlings exposed to UV-B. Six commercial cultivars were evaluated: Laura, Sprint 440, Dasher II, Exocet, Poinsett 76, and Marketmore 76 under greenhouse-controlled environmental conditions with a hydroponic sandwich-type system with a Hoagland II nutrient solution. Seedlings were irradiated from expanded cotyledons to the third true leaf with three intensities of UV-B radiation (30, 40, and 50 �ÊW cm-2) for 18 d between 11:40-15:40 h. Seedling growth, morphology, accumulation of photosynthetic pigments, and absorbing UV-B pigments were evaluated. �eLaura�f was the least affected by chlorosis and had a total absence of leaf curl, whereas �ePoinsett 76�f was the most affected in the 40 and 50 �ÊW cm-2 intensities. Both leaf area and seedling height of �eMarketmore 76�f and �ePoinsett 76�f had the lowest values. �eLaura�f obtained the highest value in both fresh weight and dry weight. �ePoinsett 76�f had the least amount of pigments absorbing UV-B and was 53% lower than that obtained by �eLaura�f. �ePoinsett 76�f had lower chlorophyll and carotenoids. Parameters used were indicators of the seedling response to UV-B radiation, but could not be used for cucumber seedling sensitivity to UV-B radiation.