PHOTOSYNTHETICA

Photosynthetica 2010, 48(4):580-588 | DOI: 10.1007/s11099-010-0075-7

Seasonal variation of photosynthesis and photosynthetic efficiency in Phalaenopsis

B. Pollet^1,*, K. Steppe¹, P. Dambre², M. C. Van Labeke³, R. Lemeur¹

¹ Laboratory of Plant Ecology, Department of Applied Ecology and Environmental Biology, Ghent University, Ghent, Belgium

² Research Centre for Ornamental Plants (PCS), Destelbergen, Belgium

³ Department of Plant Production, Ghent University, Ghent, Belgium

Nowadays, a quest for efficient greenhouse heating strategies, and their related effects on the plant's performance, exists. In this study, the effects of a combination of warm days and cool nights in autumn and spring on the photosynthetic activity and efficiency of Phalaenopsis were evaluated; the latter, being poorly characterised in plants with crassulacean acid metabolism (CAM) and, to our knowledge, not reported before in Phalaenopsis. 24-h CO₂ flux measurements and chlorophyll (Chl) fluorescence analyses were performed in both seasons on Phalaenopsis 'Hercules' exposed to relatively constant temperature regimes, 25.5/24.0°C (autumn) and 30/27°C (spring) respectively, and distinctive warm day/cool night temperature regimes, 27/20°C (autumn) and 36/24°C (spring), respectively. Cumulated leaf net CO₂ uptake of the distinctive warm day/cool night temperature regimes declined with 10-16% as compared to the more constant temperature regimes, while the efficiency of carbon fixation revealed no substantial differences in both seasons. Nevertheless, a distinctive warm day/cool night temperature regime seemed to induce photorespiration. Although photorespiration is expected not to occur in CAM, the suppression of the leaf net CO₂ exchange during Phase II and Phase IV as well as the slightly lower efficiency of carbon fixation for the distinctive warm day/cool night temperature regimes confirms the involvement of photorespiration in CAM. A seasonal effect was reflected in the leaf net CO₂ exchange rate with considerably higher rates in spring. In addition, sufficiently high levels of photosynthetically active radiation (PAR) in spring led to an efficiency of carbon fixation of 1.06-1.27% which is about twice as high than in autumn. As a result, only in the case where a net energy reduction between the temperature regimes compensates for the reduction in net CO₂ uptake, warm day/cool night temperature regimes may be recommended as a practical sustainable alternative.

Keywords: chlorophyll fluorescence; CO₂ assimilation; crassulacean acid metabolism; irradiance; photorespiration; temperature; quantum yield

Received: March 10, 2010; Accepted: October 7, 2010; Published: December 1, 2010Show citation