The respiration rate analysis was carried out by gas chromatography, following Watkins et al. (2000) with minor modifications, whereby 1 g of orchid petals was transferred to a hermetic flask and retained for 1 h at room temperature. Gas samples (1 mL) were collected through silicone septum using a syringe and analyzed by a gas chromatography machine (Agilent Technologies; 6820, USA) equipped with a capillary column (2 m) at 100 C. Hydrogen (100 kPa) was used as the carrier gas with a thermal conductivity detector. The respiration rate of orchid flowers was expressed as mg CO2 kg1 h1.