Abstract:

Effects of enhanced UV-B radiation (5.0 μW/cm2) on leaf morphology and structure and the contents of photosynthetic pigment and flavonoids in Camptotheca acuminata were investigated in pots experiment. The results showed as follows: (1)The contents of chlorophyll and flavonoids, the ratio of chlorophyll a to chlorophyll b (Chla/Chlb) increased in earlier stage and decreased in later stage under enhanced UV-B radiation compared with which growing under natural light, while carotenoids content increased constantly. (2)The leaf shape asymmetry occurred because of skewing，the photosynthetic pigments distribution in leaves were uneven，the adaxial epidermis was thickened, the chloroplast structure was distorted. (3)Further studies with scanning electron microscope (SEM) observation revealed that the number of epidermal hairs and glandular trichomes increased, glandular trichomes turned shorter and wider, stomatal apparatus in abaxial epidermis were coverd by waxy and aperture decreased. Therefore, the author considered that the UV-B radiation treatment could start the defense system of Camptotheca acuminata seedling, but finally it still could do great harm to the membrane system, membrane lipid peroxidation appeared.