EFFECTS OF LIGHT-INTENSITY AND CO2 CONCENTRATION ON GROWTH OF BANANA PLANTS (MUSA AAA, CULTIVAR PETITE-NAINE) IN-VITRO AND SUBSEQUENT GROWTH FOLLOWING ACCLIMATIZATION

The development of micropropagated banana plants during the in vitro g rowth phase prior to acclimatization was studied both in tight vessels under two different photosynthetic photon flux densities (PPFD of 30 and 240 mu mol m(-2) s(-1)) and in continuously flushed vessels under three atmospheric CO2 concentrations (0.034, 0.24 and 4.0%) at 240 mu mol m(-2) s(-1) PPFD. In tight vessels at low PPFD, the CO2 originatin g from dark respiration was partially fixed during the light period, i ndicating photosynthetic activity by the plants in vitro. At high PPFD , CO2 originating from dark respiration was rapidly fixed in the early hours of the light period and CO2 concentration became the limiting f actor for photosynthetic activity. Plants in vitro grown under high PP FD accumulated 2.3 times the dry matter achieved by plants in low PPFD . However, this developmental advantage acquired in vitro was not main tained ex vitro at the end of the acclimatization phase (on a leaf are a basis). In continuously flushed vessels, treatments with 0.24% and 4 .0% CO2-enriched atmospheres enhanced dry matter accumulation in vitro by 1.6 and 2.3 times, respectively, as compared to a 0.034% CO2 treat ment. Twenty days after transfer ex vitro, the development of plants ( on a leaf area basis) from these CO2 treatments was no longer signific antly different. The relative growth rate ex vitro was lower for plant s cultured in a CO2-enriched atmosphere in vitro than for those cultur ed at 0.034% CO2.