Influence of Sucrose Concentration on Photosynthetic Performance of Guzmania 'Hilda' In Vitro

Tissue culture is a commonly used technique for the propagation of bromeliads. In the presented work the influence of sucrose in the tissue culture media on the photosynthetic performance and growth of the bromeliad Guzmania 'Hilda' was evaluated. At the start of the in vitro phase sucrose plays a pivotal role in providing carbohydrate sources but concomitantly it might also constitute a trigger for feedback inhibition for photosynthesis. Therefore the application of sucrose was studied in more detail by exposing the in vitro plants to different exogenous sucrose concentrations (5, 12.5, 25 and 40 g/L) in the rooting medium (final stage). The amount of sucrose showed a positive relationship with both biomass formation and dawn CO2 concentrations in the culture containers. The CO2 uptake capacity was comparable for plants grown on 12.5, 25 and 40 g/L sucrose, but significantly lower for plants grown on 5 g/L sucrose during rooting stage. The initial sucrose concentration was already depleted after 4 weeks in all treatments except for the highest initial concentration, where complete eradication took 8 weeks. As such, sucrose is unable to interfere with in vitro photosynthetic performance. However, high concentrations of hexoses (glucose and fructose) were present in the medium but did not suppress photosynthesis as a higher CO2 uptake capacity and biomass formation did occur on initial sucrose enriched culture media.