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Title: Photosynthetic utilization of radiant energy by CAM Dendrobium flowers
Authors: Khoo, G.H.
He, J.
Hew, C.S. 
Keywords: 14CO2 fixation
Chlorophyll fluorescence
Irradiation stress
Saturation irradiance
Issue Date: 1997
Citation: Khoo, G.H., He, J., Hew, C.S. (1997). Photosynthetic utilization of radiant energy by CAM Dendrobium flowers. Photosynthetica 34 (3) : 367-376. ScholarBank@NUS Repository.
Abstract: 14CO2 fixation was observed in orchid Dendrobium flowers; its rate decreased with the flower development. Chlorophyll (Chl) fluorescence in different developmental stages of flowers was compared to other green plant parts (leaf, inflorescence stalk, and fruit capsule). The photochemical efficiency of photosystem 2 (PS2) (F(v)/F(m)) of a leaf was 14-21 % higher than that of a mature flower perianth (sepal, petal, and labellum) which had a much lower total Chl content and Chl a/b ratio. A higher quantum yield of PS2 (Φ(PS2)) than in the mature flowers was observed in all green parts. Flower sepals had higher Chl content, Chl a/b ratio, and F(v)/F(m) values than the petal and labellum. During flower development the Chl content, Chl a/b ratio, F(v)/F(m), and q(N) decreased while Φ(PS2) and q(P) remained constant. An exposure of developing flowers to irradiances above 50 μmol m-2 s-1 resulted in a very drastic drop of Φ(PS2) and q(P), and a coherent increase of q(N) as compared to other green plant organs. A low saturation irradiance (PFD of 100 μmol m-2 s-1) and the increase in q(N) in the flower indicate that irradiation stress may occur since there is no further protection when the flower is exposed to irradiances above 100 μmol m-2 S-1. A low Chl/carotenoid ratio in mature flower perianth as a consequence of Chl content reduction in the course of flower development suggests a relief of irradiation stress via this mean.
Source Title: Photosynthetica
ISSN: 03003604
DOI: 10.1023/A:1006807900507
Appears in Collections:Staff Publications

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