Optimization of light intensity and nitrogen concentration in solutions regulating yield, vitamin C, and nitrate content of lettuce

ABSTRACT

Light intensity and nitrogen concentration in nutrient solutions are two main factors affecting the growth and nutritional quality of lettuce(Lactuca sativa L.). This study investigated the method of regulating vegetable cultivation through the interactive control of the light environment and solution ratio. A quadratic regression orthogonal model was developed to understand the role of light intensity (43 to 237 µmol m⁻²s⁻¹) and nitrogen concentration (4.3 to 23.7 mmol L⁻¹) in lettuce growth. Dry weight, vitamin C, and nitrate contents were measured and modelled to understand the coupling effect of light intensity and nitrogen concentration on lettuce. The optimised conditions for lettuce growth were 237 µmol m⁻² s⁻¹ of light intensity and 9.2 mmol L⁻¹ of nitrogen concentration, and these conditions were predicted to produce lettuce with an average dry biomass of 3.9 g plant⁻¹, 149.9 µg g⁻¹ of Vitamin C, and 212.1 µg g⁻¹ of nitrate content based on their respective weighting factors (0.50, 0.25, and 0.25). The lettuce yield and quality were verified using the modelled optimised growth conditions and the lettuce grown was indeed more nutritional compared to the commercially available lettuce. The findings are important for mass production of lettuce in plant factories and greenhouses.

KEYWORDS:

• Interaction of light intensity and nitrogen
• lettuce yield
• modelling validation
• nitrate content
• vitamin C

Disclosure statement

No potential conflict of interest was reported by the authors.

Supplementary material

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Additional information

Funding

This work was financially supported by the Pre-research Programme on Manned Spaceflight (PR China, No. 020302), the grant from the National Natural Science Foundation of China (31870852) and the Fundamental Research Funds for the Central Universities.