The Correlation between CO2 Uptake of CAM Dendrobium Hybrid and Environmental Factors under Shade Net House Conditions

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D. Boonchai
P. Boonkorkaew
P. Kasemsap


The diurnal net CO2 uptake in Dendrobium ‘Khao Sanan’ leaves was measured year-round (June 2010 to April 2011) and integrated to obtain total CO2 uptake under commercial shade net house conditions. Seasonal changes varied between 20−40 °C air temperature, 42−94% relative humidity (RH) and 667 μmol m-2 s-1 maximum light intensity, while Den. ‘Khao Sanan’ leaves performed typical CAM photosynthesis and reached their highest net CO2 uptake rate of 4 μmol m-2 s-1 after midnight and in the early morning under a 12 ± 0.5 hours photoperiod. Total CO2 uptake during the nighttime, daytime and in a total of 24 hours (daily) increased significantly and had a maximal value of more than 2 to 2.5 folds in December and February compared with the other months. The net CO2 uptake values were correlated with temperature (r2 = 0.41), RH (r2 = 0.25) and light intensity (r2 = 0.06). The net CO2 uptake were positive between 22−29°C, 60−90% RH and less than 200 μmol m-2 s-1 light intensity conditions. CO2 uptake during the nighttime and daytime was most affected by temperature, while total CO2 uptake had a higher correlation with temperature and RH. The results of this study contribute to improve the ability to efficiently design and manipulate a semi-controlled greenhouse for Dendrobium orchids for commercial scale production in Thailand.

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