Mobile light in roses

In order to quantify the claimed differences between mobile and static lighting, and to clarify the mechanisms causing these differences, an experiment with rose `First Red¿ was carried out. In a greenhouse compartment half of the area was equipped with mobile lamps, and the other half with static lamps. By mounting the lamps in the centre of the greenhouse, a light gradient was achieved in both treatments. Experimental plots were chosen with daily light integrals of 1 to 3 and 3 to 5 mol m-2 day-1 respectively. A `traditional¿ and a `synchronous¿ (production in flushes) crop were grown. Production and photosynthetic characteristics were measured during the winter season 2003 ¿ 2004. Photosynthetic characteristics were measured in the synchronous crop. With the INTKAM simulation model for rose, production under diverse mobile lighting regimes was predicted. Fresh weight production over the experimental period was higher in the static-light treatment than in the mobile-light treatment for both the traditional as well as the synchronous crop. This was caused by a lower number of stems per plant and a slightly lower weight per stem under mobile lighting. Length of stems was not affected. The light response curves for leaves did not differ between the treatments. Also, the induction of photosynthesis after a simulated light pulse in a cuvette was the same for both treatments. Simulation of the growth of the synchronous crop showed that a different lamp speed or a combination of fixed and moving lamps confirmed the conclusion that mobile lighting did not lead to increased production in comparison with static lighting at similar daily amounts of lamplight.