Abstract:
Salinity is one of the major abiotic stresses that affects the productivity of plants, including orchids and caused an abnormal growth as well as reduced the quantity or quality of productivity. Dendrobium is an important economic plant in Thailand. It uses as cut flowers and potted plants which are exported and made a top income for the country. However, salt stress is one of the factors that limits Dendrobium growth and development. Therefore, in this research was aimed to study the effect of sodium chloride (NaCl) at the concentrations of 0, 100, 200 and 300 mM and the appropriate concentration of proline or paclobutrazol (PBZ) in order to reduce the negative effects of NaCl on in vitro growth of Dendrobium. This experiment was compared the 2 methods of application 1. Dendrobium is treated with proline at the concentration of 0, 1.25, 2.5, 5.0, 7.5 and 10.0 mM or PBZ at the concentration of 0, 1.7, 3.4, 6.8, 13.6 and 27.2 µM under salt stress condition and 2. Dendrobium cultured on proline or PBZ at various concentrations as mention previously for 7 days before transferred to salt stress condition. The result showed that the concentrations of NaCl up to 200 mM decreased the growth of Dendrobium. While Dendrobium cultured on VW supplemented with proline at the concentration of 5.0 mM or PBZ at the concentration of 6.8 µM for 7 days prior to transfer to salt stress condition gave the best result to alleviate negative effects from NaCl. Proline at the concentration of 5.0 mM and PBZ at the concentration of 6.8 µM also increase proline and total soluble sugar accumulation and activity of superoxide dismutase (SOD) and catalase (CAT) and lower malondialdehyde (MDA) content and percentage of electrolyte leakage (EL). Consequently, proline and PBZ at the appropriate concentration are able to reduce the negative effect of NaCl on Dendrobium.