Low Exogenous Sucrose Improves Ex Vitro Growth and Photosynthesis in Coconut In Vitro Plantlets if Grown In Vitro under High Light

The effects of sucrose concentration in the medium at 0.0, 22.5, 45.0 and 90.0 g L -1 on in vitro and ex vitro growth and photosynthetic parameters at 40 (standard growth-room condition) or 400 μmol m -2 s -1 photosynthetic photon flux density (PPFD) were studied. In vitro zygotic embryos cultured with low sucrose concentration (22.5 g L -1 ) had positive effect on Rubisco protein and activity, net photosynthesis, chlorophyll fluorescence and PPFD and ci responses. However, in this growth-room condition of light plantlets grown in vitro with intermediate sucrose influenced positively survival, ex vitro growth and photosynthesis under low photosynthetic PFD. In the case of light irradiance treatments, coconut plantlets were grown at not limiting condition of CO2 of 1400 μmol mol -1 at low and high irradiance provided by halogen lamps (Osram, Westfield, USA). Photosynthetic parameters were significantly higher in low sucrose concentration in the medium under low light irradiance. Plantlets grown under high light intensity and low sucrose in the medium had the best effect on the growth and photosynthetic parameters.