Research in the project 'Grip on Light' focusses on saving energy during cultivation of pot plants. Flowering in Phalaenopsis was induced in October 2013 by lowering the greenhouse temperature and supplemental lighting (100 micromol/m2/s). With three Plantivity fluorometers the induction of photosynthesis of three cultivars was monitored during the low temperature and supplemental lighting treatment.
Within 15 min. after the start of lighting some photosynthesis activity was detected, but it took 3-5 hours before photosynthesis had reached its steady state. Based on the Monitoring-PAM data it was estimated that this slow induction of photosynthesis has a significant impact on the light use efficiency of supplemental light. In a case where photosynthesis induction is immediate, the efficiency of the supplemental light would have been 25-30% higher over the first 6 hours of supplemental lighting. On a few extreme days this figure would have been 50% for the slowest cultivar (Golden Beauty). It is not yet clear why photosynthesis induction in Phalaenopsis takes so long. It is, however, clear that significant energy saving on lighting could be achieved by using photosynthesis monitoring to adjust supplemental lighting to the photosynthesis capacity of the crop.
The project was funded by the Product Board of Horticulture and the Dutch Ministry of Economic Affairs and was carried out by Wageningen UR Greenhouse Horticulture as part of the Innovation Programme Greenhouse as Energy Source and the Biosolar Cells programme with additional support from Guardian and Ludvig Svensson.