Effects of CO₂ concentration, PPFD and sucrose concentration on Cymbidium plantlet growth in vitro

Leafy Cymbidium protocorm-like bodies (PLBs) were cultured in vitro for 42 days on a half strength Murashige & Skoog (1962) agar (7 g l^-1) medium with (30 g l^-1) or without (0 g l^-1) sucrose under four different environmental conditions of CO₂ concentrations (500 or 1000 μmol mol^-1) and photosynthetic photon flux density (PPFD) levels (50 or 100 μmol m^-2 s^-1). On day 15, all plantlets were transferred to new media with or without sucrose. The sucrose concentrations, before and after day 15, were varied or unvaried. This allowed a total of 16 treatments to be completed for this experiment. On day 42, fresh weight, dry weight, leaf area per plantlet, and net photosynthetic rate (NPR) per total dry weight were significantly greater under 1000 μmol mol ^-1 CO₂ and 100 μmol m^-2 s^-1 PPFD than conventionally grown plantlets (500 μmol mol^-1 CO ₂, 50 μmol m^-2 s^-1 PPFD and media with sucrose before and after day 15). The above results show that Cymbidium plantlets could be grown effectively on the medium without sucrose (i.e., photoautotrophically) under enriched CO₂ and high PPFD conditions.