Carbon sources of tissue-cultured plantlets are sugars, for example, sucrose added to the culture medium or C02 assimilated by photosynthesis. Since the plantlets have been shown to have insufficient photosynthetic activity1,2), the sugar added to the medium is thought to be the main carbon source. found that photosynthetic activity of tissue-cultured plantlets was increased under high photosynthetic photon fluxes (PPF) and C02-enriched conditions. They3-5) further showed that growth of

more »

... s under these conditions was greater than that under conventional in vitro conditions. Shiba and Nagaoka6) also reported that growth of carrot plantlets derived from somatic embryo was stimulated by ventilating C02-enriched air under a high PPF. These results indicate that CO2 serves as a carbon source under suitable conditions for photosynthesis. There has been, however, no quantitative analysis on the effectiveness of sugar and C02 as the carbon source which plantlets utilize.