Potential to steer crop with blue light
Even though plants don’t have eyes, they can “see” whether it is day or night, determine the length of a day and see the colour of the light. They do this by using light sensitive pigments. But besides being their eyes these pigments are also control centres: they send instructions which impact crop development. These are very complicated processes with many intermediate steps not all of which are known. But in recent years our knowledge about them has grow enormously.
Blue light
There are different types of light sensitive pigments: cryptochromes, phototropins, phytochromes, ZTL and UVR8. Each responds to a certain part of the light spectrum. The first two are important for blue light.
As is common in plants, these pigments do not have just one function, but they steer several processes. Cryptochromes and phototropins have an affect on the biological clock, growth towards light, opening of the stomata, elongation of the plant, bud development and the shape of the leaves. This means that these processes can be steered with extra blue light (such as LEDs) or by reflecting a part of the blue light with the coating ReduFlex Blue.
However, this is not a simple operation because it not only involves blue light but also, for example, the relationship with red light. Other pigments, the phytochromes, respond directly to this light colour.
Club of 100
Financed and supervised by the Dutch Club of 100, of which Mardenkro is also a member, Wageningen UR Greenhouse Horticulture has been researching the possibilities of steering with light colour. At the moment the most potential seems to lie in steering plant length. While you want pot plants to remain compact, cut flowers such as roses should preferably be longer. This can be achieved by altering the relationship between blue and red in the light.
Sunlight naturally contains 31% blue light, so a relatively high proportion. Therefore, as research shows, adding just a little blue light has little impact on tomato and pot plants. The ratio of blue:red has to change significantly. In addition to the blue:red ratio, altering the ratio of red:far red at the end of the day can have a greater effect, according to research on fuchsias. Relatively more blue during the day, and relatively more red at dusk (compared with far red) results in more compact fuchsias. No effects were noticed in hibiscus. Research will continue in the autumn and this will look at the opportunities offered by coatings.
ReduFlex Blue
Less blue light can lead to more elongation which is desirable for cut roses. The proportion of blue in natural light can be reduced by using the coating ReduFlex Blue. Research carried out by Delphy (previously DLV) and the experiences of growers show that roses grown under the coating can have longer sems; the amount depends on the variety.
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