title: Effects of shade treatments on photosynthetic characteristics, chloroplast ultrastructure, and physiology of Anoectochilus roxburghii.
abstract: Anoectochilus roxburghii was grown under different shade treatments-50%, 30%, 20%, and 5% of natural irradiance-to evaluate its photosynthetic characteristics, chloroplast ultrastructure, and physiology. The highest net photosynthetic rates and stomatal conductance were observed under 30% irradiance, followed in descending order by 20%, 5%, and 50% treatments. As irradiance decreased from 50% to 30%, electron transport rate and photochemical quenching increased, while non-photochemical quenching indexes declined. Reductions in irradiance significantly increased Chl a and Chl b contents and decreased Chl a/b ratios. Chloroplast ultrastructure generally displayed the best development in leaves subjected to 30% irradiance. Under 50% irradiance, leaf protein content remained relatively stable during the first 20 days of treatment, and then increased rapidly. The highest peroxidase and superoxide dismutase levels, and the lowest catalase activities, were observed in plants subjected to the 50% irradiance treatment. Soluble sugar and malondialdehyde contents were positively correlated with irradiance levels. Modulation of chloroplast development, accomplished by increasing the number of thylakoids and grana containing photosynthetic pigments, is an important shade tolerance mechanism in A. roxburghii.
authors: The Nurturing Station for the State Key Laboratory of Subtropical Silviculture, Zhejiang A & F University, Hangzhou, China.
authors: Qingsong
authors: Q
authors: Shao
authors: The Nurturing Station for the State Key Laboratory of Subtropical Silviculture, Zhejiang A & F University, Hangzhou, China.
authors: Hongzhen
authors: H
authors: Wang
authors: Zhejiang University, Hangzhou, China.
authors: Haipeng
authors: H
authors: Guo
authors: The Nurturing Station for the State Key Laboratory of Subtropical Silviculture, Zhejiang A & F University, Hangzhou, China.
authors: Aicun
authors: A
authors: Zhou
authors: The Nurturing Station for the State Key Laboratory of Subtropical Silviculture, Zhejiang A & F University, Hangzhou, China.
authors: Yuqiu
authors: Y
authors: Huang
authors: The Nurturing Station for the State Key Laboratory of Subtropical Silviculture, Zhejiang A & F University, Hangzhou, China.
authors: Yulu
authors: Y
authors: Sun
authors: Zhejiang Shouxiangu Rare Botanical Institute, Wuyi, China.
authors: Mingyan
authors: M
authors: Li
mesh_terms: D002734:Chlorophyll / Q000378:metabolism*; D002736:Chloroplasts / Q000000981:diagnostic imaging*; D003624:Darkness; D008315:Malondialdehyde / Q000378:metabolism; D029595:Orchidaceae / Q000502:physiology*; D010788:Photosynthesis / Q000502:physiology*; D018515:Plant Leaves; D013472:Sunlight; D013482:Superoxide Dismutase / Q000378:metabolism; D014463:Ultrasonography
chemical_list: D002734:Chlorophyll; D008315:Malondialdehyde; D013482:Superoxide Dismutase