AOBPreview originally published online on April 13, 2005
Annals of Botany 2005 96(1):43-49; doi:10.1093/aob/mci146
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Published by Oxford University Press on behalf of the Annals of Botany Company 2005
Photosynthesis in Relation to Reproductive Success of Cypripedium flavum
1 Kunming Institute of Botany, the Chinese Academy of Sciences, Kunming 650204, China and 2 Graduate School of the Chinese Academy of Sciences, Beijing 100039, China
* For correspondence. E-mail huhong{at}mail.kib.ac.cn
Received: 6 November 2004 Returned for revision: 1 February 2005 Accepted: 28 February 2005 Published electronically: 13 April 2005
Background and Aims Cypripedium flavum is a rare, endemic alpine slipper orchid of China, which is under threat from excessive collection and habitat changes. Conservation and re-introduction of C. flavum is restricted by lack of knowledge of the plant's photosynthesis and how that affects reproductive success. The hypothesis is tested that reproductive success is determined by photosynthetic production.
Methods To understand the photosynthetic characteristics and adaptation of C. flavum to alpine environments, and the relation to reproductive success, measurements were made at four field sites with varying degrees of forest cover in the Hengduan Mountains, south-west China.
Key Results Both photosynthetic capacity and reproductive traits of C. flavum are affected by light availability. Photosynthetic rate (A) is greatest around noon, following the pattern of photosynthetically active radiation (PAR) at all sites. Cypripedium flavum has highest daily mean photosynthetic rate (Adaily) and light-saturated photosynthetic rate (Amax) under a half to a third of full sunlight. High radiation decreased A. However, the optimum temperature for photosynthesis was similar (1820 °C) at all sites.
Conclusions The quotient of daily mean photosynthetic rate to light saturated photosynthesis (Adaily/Amax) is positively correlated with the ramet number m2 and percentage of fruiting of C. flavum. The Adaily/Amax ratio is a useful proxy for evaluating reproductive success of C. flavum.
Key words: Cypripedium flavum, photosynthesis, light availability, plant reproductive success