• FLOWER RESEARCH JOURNAL
• /
• v.17 no.4
• /
• pp.237-241
• /
• 2009

This study was conducted to determine injury symptoms of orchids by sulfur dioxide gases, three orchid plants (Phalaenopsis, Cymbidium, Oncidium) were exposed to sulfur dioxide gas in an enclosed growth chambers. Sulfur dioxide gases treatments consist of five different concentrations (0, 5, 10 25, and 50 ppm) and plant exposure of 18 hours with $25{\pm}5^{\circ}C$ air temperature and $50{\pm}5%$ relative humidity. SPAD values for chlorophyll content and percent leaf injury as well as leaf ion exudation were measured before and after the gas treatments. Phalaenopsis leaves showed 23.3% leaf injury at 10 ppm sulfur dioxide gas, whereas Cymbidium and Oncidium showed 4.0 and 4.4% leaf injury under 25 ppm or less, respectively. Major leaf injury symptoms appeared as initial water-soaking under side of the leaf, followed by rapidly progressed complete leaf discolorization or chlorosis. As the gas concentration increased, the SPAD value decreased while ion exudation increased. Cymbidium and Oncidium were resistant to sulfur dioxide gas than Phalaenopsis.