Effect of light intensity and CO2 concentration on growth and the acquisition of in vivo characteristics during acclimatization of grapevine regenerated in vitro>

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This study reports the effects of light intensity and CO2 concentration during the acclimatization of in vitro plantlets of grapevine (Vitis vinifera L. cv. Touriga Nacional) on growth, chlorophyll and soluble carbohydrate contents, stomatal index and regulation of water loss. After in vitro phases at 45 µmol m-2 s-1 PFD, plantlets were transferred directly from in vitro to ex vitro acclimatization at different irradiation intensities (150 and 300 µmol m-2 s-1) and CO2 concentrations (350 and 700 µl l-1). Growth, especially total biomass, was closer associated with light than with CO2. Ex vitro leaves, expanded at high light and high CO2, developed fully autotrophic characteristics, mainly with regard to specific leaf area, chlorophyll a/b ratio and down-regulation of sucrose accumulation. In all treatments stomatal indices of leaves were lower than those of in vitro leaves although regulation of water loss was reduced at high CO2.