Growth, Morphology, and Photosynthetic Activity of Chinese Cabbage and Lettuce Grown under Polyethylene and Spectrum Conversion Films

Abstract

The intensity and spectrum of light affect the growth and morphology of vegetables grown in greenhouses. Although many studies have attempted to improve plant growth by converting the light spectrum using functional films, their effects were different and the reasons were not clear. The objective of this study was to investigate the effect of spectrum conversion film (SCF) on the photosynthetic activity and growth of Chinese cabbage (Brassica rapa L. ssp. pekinensis) and romaine lettuce (Lactuca sativa L. var. longifolia). From April to May 2021, the two leafy vegetables were grown under a SCF and a polyethylene film (control). The SCF absorbs low photosynthetic efficiency wavelengths (280400 nm or 500600 nm) and emits high photosynthetic efficiency (400500 nm or 600700 nm). The electron transport rates of photosystem II and I, and the photosynthetic rate of Chinese cabbage grown under the SCF were significantly increased compared to the control. The leaf dry weight, leaf area, and leaf thickness of Chinese cabbage grown under the SCF was also significantly increased by 33.0%, 33.3%, and 32.4%, respectively, compared to the control. However, the lettuce grown under the SCF showed no difference in photosynthetic activity, growth, and morphological characteristics compared to the control. The different effects of spectrum modification between the two films are presumed to be due to the difference in leaf light absorption and chlorophyll content between two vegetables. From the result, it was concluded that the leaf optical properties and chlorophyll content of plants can help determine whether the SCF is effective or not.