Abstract: Camellia nitidissima is shadetolerant and has a limited photosynthetic potential of acclimating high light. The effects of different shading levels (8%, 25%, 50% and 100% of full sunlight) on the growth, biomass, chlorophyll fluorescence parameters of C.nitidissima seedlings were examined in order to know the growth and physiological responses of C.nitidissima to strong light. The growth of C.nitidissima seedlings were inhibited under different strong light stress. As the strong light stress was enhanced, the color of C.nitidissima seedlings leaves turned into light green and yellow green from dark green, leaf burning was getting worse, time of shooting was delayed and the shoots grew poor, the death rate increased. The biomass of root, stem, leaf and total plant significantly decreased with the strengthened stress. The strong light stress had the most influence on leaf biomass, followed by root biomass, and then the stem biomass. With the increasing strong light stress, the contents of total chlorophyll (Chl), chlorophyll a (Chla) and chlorophyll b (Chlb) in leaves of C.nitidissima seedlings significantly decreased, while Chla/Chlb and Car/Chl increased. The chlorophyll fluorescence parameters F_o, F_m, F_v, F_v/F_o, F_v/F_m all decreased under strong light stress, which indicated that with the increasing of strong light stress, the reaction center of PSⅡ was destroyed, photosynthetic electron transform capability was weakened and photosynthesis was restrained.

Key words: endangered plant, Camellia nitidissima, strong light stress, growth, chlorophyll fluorescence