Experimental photo-biological studies have been carried out to find effective stable spectral PAR fluxes for cultivating tomato seedlings and to estimate the effect of the change in the spectral irradiation mode during the growing season under electrical light.
The purpose of the study was to test the capabilities of the newly developed LED irradiators with an adjustable PAR radiation spectrum to estimate the effectiveness of spectral irradiation modes to treat tomatoes for the formation of high-quality seedlings and to increase tomato yields by changing the PAR radiation spectrum during the plant flowering stage under electrical light.
The study showed that for the formation of high-quality seedlings with a well-developed photosynthetic apparatus and a well-formed habitus, the most favourable was the PAR spectrum with proportions of blue (400–500) nm and red (600–700) nm rays of about 30 % and green (500–600) nm – about 40 % in a three-component PAR flux.
The change of the spectral irradiation mode during the stage of mass fruiting of tomato plants grown for fruit production, namely, an increase in the proportion of radiation in the red (600–700) nm spectral region by 15 % at the expense of the green (500–700) nm spectral region, caused tomato fruits to ripen 20 days earlier. Parameters of the biochemical composition of the fruits (carbohydrate and vitamin C contents) were also higher in the treatment with the change of spectrum. The experiments demonstrated that by changing the spectrum of the prototypes of the phosphor LED irradiators with the adjustable spectrum in certain stages of plant growth, these irradiators could be effectively used to cultivate long-season crops (for example, tomatoes).
The results obtained can be used to select spectral irradiation modes for producing greenhouse tomato seedlings and growing fruit-bearing tomato plants under electrical light in northern regions and in isolated spaces in various climatic zones using “City-farm” technologies.
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• spectral radiation efficiency
• variable radiation spectrum
• phosphor LED irradiators
• tomato seedlings
• tomato productivity