Effects of Light Intensity on the Growth and Related Physiological Indexes of Bretschneidera sinensis

Container seedlings of Bretschneidera sinensis from Jiangshan, Zhejiang with 4 different natural sunlight treatments in open field during the whole growing season were used to compare and analyze growth and morphological indexes, chlorophyll content, photosynthetic characteristics and other physiological indexes of seedlings explore the suitable light conditions for the growth of B. sinensis seedlings. The results showed that the increases in height and caliper, biomass of seedlings under the three low-light intensity treatments were all higher than 100% light intensity treatment, increasse in height and caliper of 30% light intensity treatment was 1.65 and 1.44 times of 100% light intensity treatment, and the biomass of seedlings was 2.67 times of 100% light intensity treatment. The thickness of the leaves of different treatments continued to increase, but at the end of the test there was no significant difference. The specific leaf weight of 30% light intensity treatment was the lowest, while that of 100% light intensity treatment was significantly higher than that of other 3 treatments throughout the test period. From August to October, the chlorophyll content changed from shading treatment significantly higher than 100% lighting to 100% lighting significantly higher than shading treatment. The transpiration rate (Tr) of the 100% light intensity treatment was highest, but the water use efficiency (WUE) was lowest. However, WUE and the growth of 30% light intensity treatment were all the best. Therefore, B. sinensis seedlings were not resistant to strong light, should to be properly shaded in summer with 30% light intensity as the best.