Reduction of the ozone layer results in the increase in ultraviolet radiation reaching the earth's surface, especially the ultraviolet-B (UV-B). The increase of radiation may induce structural and physiological changes in plants, influencing their growth and development. This paper evaluates the effects of ambient UV-B radiation upon to the leaf morphology of Arabidopsis thaliana developed under controlled conditions. The seeds of A. thaliana grown in environmental chamber, with 300 µmol m-2s-1 de photosynthetically active radiation (PAR) with and without 6 kJ m-2 s-1 of radiation UV-Bbe (UV-Bbe; UV-B biologically effective). After 21 days, ten leaves of each treatment (with and without UV-B radiation) were collected to measure leaf area, fresh and dry mass, AEF, stomata and trichome densities of both leaf surfaces, leaf thickness and concentration of phenolic compounds and total chlorophyll, and chlorophyll a and b. Leaves treated with UV-B radiation presented smaller leaf area, fresh and dry weight, hair density, and stomata density on the adaxial epidermis. However, leaves treated with UV-B presented higher mean values for total thickness, mesophyll thickness, higher concentration of total chlorophyll, chlorophyll a and b, and phenolic compounds when compared to leaves without UV-B radiation. These significant morphological differences (p < 0.05) between leaves treated with and without UV-B radiation indicate that A. thaliana is not insensible to UV-B radiation and possess mechanisms that minimize the negative effects on leaf development and growth. Although, the plant responses to UV-B radiation involves several physiological mechanisms, that need more detailed investigation.
Arabidopsis thaliana; UV-B radiation; leaf morphology; phenolic compounds
