Possible reasons of a decline in growth of Chinese cabbage under a combined narrowband red and blue light in comparison with illumination by high-pressure sodium lamp

• RBL caused decrease in fresh and dry mass accumulation of Chinese cabbage plants.
• RBL increased maximal photosynthetic capacity of Chinese cabbage chloroplasts.
• RBL does not lead to excessive oxidative stress versus HPSL light.
• RBL apparently is not responsible for the end-product inhibition of photosynthesis.
• RBL hardly penetrates through plant canopy compared with HPSL light.

We attempted to elucidate possible reasons of a decline in fresh and dry mass accumulation by Chinese cabbage (Brassica chinensis L.) plants under combined narrowband red and blue light emitting diodes (LEDs) in comparison with illumination by a broad-spectrum high-pressure sodium lamps (HPSL) of equal photosynthetically active radiation intensity. Analysis of photosynthetic activity, sugar content and composition, antioxidant activity, and membrane peroxidation revealed neither inhibition of nor damage to the photosynthetic apparatus. There was also no detectable oxidative stress and related photoassimilate loss, the source-sink relations were also unimpaired in LED-grown plants. Our findings suggest that the light distribution in the plant canopy might be an essential factor limiting plant growth under the LED light. The results are discussed in view of the role of the radiation in the yellow–green range of the spectrum in driving photosynthesis.

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