PHOTOAUTOTROPHIC MULTIPLICATION OF CYMBIDIUM PROTOCORM-LIKE BODIES

An experiment was conducted to compare the multiplication and growth of the Cymbidium protocorm-like bodies (PLB) under photoautotrophic (0 g· l^-1 sucrose in the medium) and photomixotrophic (20 g· l^-1 sucrose in the medium) conditions in the presence of either 0.01 or 1.00 mg· l^-1 naphthaleneacetic acid (NAA) and 0.6 or 3.5 h^-1 number of vessel air exchanges. The PLB were cultured on a 30 ml half strength Murashige and Skoog agar (8 g· l^-1) medium containing 1.0 mg· l^-1 kinetin. All cultures were maintained at 25°C, under 70 μmol· m^-2· s^-1 photosynthetic photon flux density (PPFD) and 340–430 μmol· mol^-1 CO₂. Number of vessel air exchanges and NAA concentrations had no significant effect on the growth and multiplication of PLB. Multiplication rate of PLB under photoautotrophic condition were comparable to those of PLB under photomixotrophic condition. Stomatal density, and chlorophyll content and net photosynthetic rate (NPR) per gram dry weight were significantly greater in photoautotrophic condition than in photomixotrophic condition. Total dry weight of the PLB was greater in photomixotrophic condition than in photoautotrophic condition. Net photosynthetic rate of PLB under various CO₂ concentrations indicated that CO₂ enrichment may promote growth and multiplication of Cymbidium PLB.