Influence of light and temperature on flower development in gerbera

Higher intensities artificial lighting are currently being installed for gerbera crops, mainly because of the relatively low costs of high-capacity HPS lamps with a higher light output. In addition, LED lighting systems are becoming even more efficient. In order to gain insight on increasing production with various high-capacity lighting systems, an experiment was performed with three lighting systems. Gerbera, cv. Kimsey was grown under HPS, hybrid (combination of HPS and LED) and under a LED lighting system in three greenhouses of 144 m2. Different light and temperature set points were used to investigate the effects of the light sum and light spectrum in combination with greenhouse air temperature and plant temperature on growth, development and production. A lower plant temperature under HPS lighting with lower air temperatures was expected to result in more generative growth, but this did not appear to be the case. Even though, gerbera under HPS during the winter months produced more flowers, but overall the differences in production under HPS and LED lighting were small. Although growers suspected that under LED-lighting, either a hybrid or LED-only lighting system, botrytis infection might increase due to the lack of radiative heat for the crop, no increase in botrytis infection was observed. Additional measurements of air and plant temperature under HPS and LED lighting were performed to investigate the influence of both factors on the initiation and development rate of gerbera flowers. These results are presented and discussed in the light of optimizing cultivation conditions for gerbera.