The Effect of New Developed Fluorescent Greenhouse Films on the Growth of Fragaria x ananassa 'Elsanta'

In order to optimise light quality and quantity for plant growth, new photoselective greenhouse covering materials were developed containing different fluorescent pigments (Blue, Red1, Red2, Red3) in different concentrations. Excitation of all fluorescent pigments took place around 365 nm. Blue pigments showed fluorescence between 410-480 nm, Red1 and Red2 pigments between 610-630 nm and Red3 pigment between 600-690 nm, while also major parts of the blue and green part of the spectrum were absorbed. Fluorescence effects of the plastic film prototypes were rising with increasing pigment concentration. However, fluorescent effects were small. While Blue pigments increased total PAR transmission with 1-3 %, Red pigments were found to lower PAR transmission. Only pigment Red3 was able to increase the red:far-red ratio with 10 %. The effect of the different film prototypes on strawberries 'Elsanta' was investigated in two experimental periods in 2002 and 2003. Blue fluorescent films seemed to be favourable for strawberry fruit production. Whether this was due to the higher PAR transmission of the films or to a light quality effect cannot be concluded from the experiments. Blue fluorescent films caused strawberry production to increase with 11 %, mainly because of an increased fruit number. On the other hand Red3 fluorescent film delayed fruit production significantly. Total yield under Red3 was 10 % lower than under the Reference film. This effect was due to the lower PAR transmission of the film and the increased red:far-red ratio. Fruit colour was only slightly influenced by the different film prototypes. Fruits grown under Blue fluorescent films were slightly brighter but more saturated than fruits grown under the Reference film, which were darker but paler. Fruits grown under Red3 fluorescent film were apparently brighter but more saturated than fruits grown under the Reference film. In experiments in 2002, that was also observed for fruits grown under the Red1 and Red2 fluorescent film. Furthermore, dry matter and ash content of the fruits were determined, as well as the electric conductivity (EC) and sucrose concentration in the fruit sap. However, no significant differences could be detected. Fruits grown under Blue films were found to be slightly more acid (lower pH) than fruits grown under the Reference film, fruits grown under the Red films were found to be less acid. Since the sweetness to sourness ratio can be used as quality index, which fairly cor