An important quality trait of pot plants is compactness. In winter, plants can elongate too much, due to the low light levels. Elongation of stems and petioles can be suppressed by growth inhibitors, resulting in more compact plants. However, the use of growth regulators is in an increasing degree under pressure and their use will be limited in the short term. It is therefore important to find alternatives. One of these alternatives is to alter the spectral composition of the light in favour of blue light to keep pot plants more compact during their cultivation.
Steering plant growth with spectral composition of the light is the topic of one of the projects that are currently supported by the members of the Club of 100 of Wageningen UR Greenhouse Horticulture. This winter, we started with a series of experiments in which Hibiscus rosa sinensis and Fuchsia plants are cultivated at 10%, 30% and 50% blue light in the Innovation and Demonstration Centre LED (IDC LED) in Bleiswijk. Furthermore, the ratio of red to far red light at the end of the day is varied to affect elongation. In this project, we aim to determine how the combination of the percentage of blue light and the red to far red ratio at the end of the day interact in affecting elongation and compactness.
During the cultivation we monitor plant elongation and the moment of flowering. Furthermore, we determine the rate of development, plant architecture, flowering, photosynthesis, stomatal conductance, and transpiration. The experiment is supervised by a selection of the companies of the Club of 100 of Wageningen UR Greenhouse Horticulture.