Abstract

A whole-plant open-system chamber was developed to measure CO₂ exchange in Phalaenopsis amabilis. The consistent and continuous curves of CO₂ gas exchange rhythms at various conditions, sampled at 1-min interval, were used to evaluate the factors affecting on the CO₂ exchange pattern. The influencing factors included the day/night temperature, sample size, light period, light intensity and water stress. The adequate growth conditions of P.  amabilis were 26 to 30°C day temperature, 20 to 22°C night temperature, 14 to 16 h light and 180 to 215 μmol m^-2s^-1 of light intensity. Water stress had the most significant effect on the CO₂ exchange pattern. The gas exchange measurement system developed in this study is a useful and reliable measurement system for studying the physiological characteristics of Phalaenopsis varieties.

Key words: CO₂ pattern, open-system, Phalaenopsis, CAM plant, water stress, light rhythms.