Colored photoselective meshes for growing berries
Solar radiation and its spectral composition regulate the many physiological responses of plants, such as the biosynthesis of flavonoids. In recent years, the effect of spectral wavelengths on the accumulation of flavonoids in fruit species has been investigated and it has been found that high solar intensities and the predominance of shorter wavelengths in the light spectrum, in the range of wavelengths of blue and UV light, generally increase the amount of flavonoids and, in particular, the anthocyanin type (AC), during the maturation, harvest and post-harvest of the fruits.
A group of European scientists investigated the effect of modified sunlight conditions, especially the increase in the proportion of blue wavelengths and the light spectrum in relation to the accumulation of AC in two species of Vaccinium (berries): the European wild blueberry (V. myrtillus L.) and Highbush cranberry culture (V. corymbosum L., cv Brigitta Blue).
Next, the anthocyanin profile of the berries once ripe. The experiment was carried out in the field in the Trentino region (Italy) during 2013 and 2014 with the application of colored photoselective meshes, to also study the interaction of light conditions with other environmental variables, such as light intensity and temperature.
The plants were covered with IRIDIUM nets (Agritenax srl, Salerno, Italy) of blue, pearl (below the so-called "white") and red when the fruits were in the green phase of immaturity. The meshes had shading of 15%, 7% and 9% according to the company's specifications, so the white and red meshes were duplicated to unify the shading between the 15% treatments as much as possible. In the case of the red mesh, doubling the layers of mesh on the crops helped prevent the passage of blue bands, thereby increasing the proportion of red light reaching the plants. The effect of the meshes was compared to plants grown under sunlight in the open field without any type of screen. Almost total light exclusion was also tested using a black mesh that prevented 90% of sunlight from passing through.
The results indicated that the light responses of the two species of Vacciniumstudied were different. Although both species are plants adapted to shading, the reduction of an 90% of the solar radiation only benefited the wild blueberry plants, which accumulated the highest content of anthocyanins in both seasons. On the other hand, the same conditions were unfavorable for the cultivated blueberries, whose ripening was delayed by at least two weeks, and the accumulation of anthocyanins was significantly reduced compared to the berries grown under sunlight.
In addition, the scientists observed that the growing season had a strong influence on the accumulation of anthocyanins in both species, in terms of the temperature flow and the composition of the light spectra during the maturation period of the berries.
The scientists conclude that the use of photoselective meshes can be a complementary agricultural practice for the species of Vaccinium. For example, the black mesh could be used in the growing attempts of wild European cranberry semi-crop to produce berries of high nutritional value and to increase the commercial value of the crop, which could be exploited in the sectors concerned. However, in the present study, the high percentage of shading affected floral induction negatively in the second year of production. Therefore, black or blue meshes with a higher percentage of shading should be preferred for cultivation purposes.
Source: Fresh Plaza
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