Effect of high scattering lamellae on growth and photosynthesis of young tomato plants : smart materials crop experiments

To investigate the effect of very high hortiscatter (extreme light diffusion) on the growth of a young tomato crop, an experiment was conducted at Wageningen UR Greenhouse Horticulture in Bleiswijk. Three levels of light diffusion were compared: high diffusion (hortiscatter=0.9), medium light diffusion (hortiscatter = 0.65) and direct light or no light diffusion (hortiscatter~0). The plants were placed on elevated growing tables and grown at a high density to simulate the high LAI values of a grown-up crop. The materials allowing for the differences in light diffusion were placed on metal frames above the plants. Each material was used on two tables. D espite a careful set up, the PAR sum was not equal for all tables. This was due to position effects in the greenhouse as well as small differences in light transmission of the covering materials. When both diffusion factor and PAR sum are considered in the analysis of the results of the successive destructive harvests, the plants grown under the high diffusing lamellae showed increased leaf area and higher fresh and dry weight compared to the other two treatments. The light use effi ciency, expressed as grams of dry matter produced per mol PAR, increased with increasing Hortiscatter for the last two destructive harvests. Net photosynthesis increased also with the increase of scattering. A larger trial in separate compartments would be desirable to verify these results in real growing conditions and evaluate the effects on fruit production during a longer experiment