Effects of presence (30 g l-1) and absence of sugar and growth regulator (IBA, 1 mg l-1) in the medium, number of air exchanges of the culture vessel (0.6 or 6.7 h-1), CO2 concentration in the culture room (400 or 1500 ^mol mol-1) and types of supporting materials (agar and Florialite) on the growth in vitro and survival percentage ex vitro of Acacia mangium plants were examined. The combination of high CO2 concentration (CO2 enrichment) and high number of air exchanges of the culture vessel increased the fresh and dry mass of the plants, while presence/absence of sugar and growth regulator did not have any significant effects (Table 28.5). The plants cultured in a conventional way (with sugar and IBA containing agar medium in the culture vessel and with low number of air exchanges under low CO2 concentration in the culture room) gave the lowest fresh and dry mass, and no root formation, while rooting of the plants was enhanced in other treatments (Fig. 28.4). Net photosynthetic rate was higher throughout the culture period in the treatment with sugar-free Florialite supporting material in the culture vessel with high number of air exchanges under high CO2 concentration (data not shown).
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