Growth and Physiological Responses of ChineseCabbage to Different Light Intensity Until LeafyHead Formation

Abstract

The effects of light on the growth, leaf morphology, physiological responses, and quality of Chinese cabbage (Brassica campestris L. ssp. pekinensis) were examined at five light intensity levels (200-1,000 μmol·m-2 ·s-1 ) to determine the optimal light intensity for the production of high-quality cabbage heads. In each light treatment, peak irradiance values at midday were 200 (I), 400 (II), 600 (III), 800 (IV), and 1,000 (V) μmol·m-2 ·s-1 . Fresh and dry weights of plant shoots significantly increased with light intensity; leaf number and area were positively correlated with light intensity, although the total and mean leaf area for plants in group IV exceeded that of group V. The leafy head formation was observed in high light intensity (800 and 1,000 μmol·m-2 ·s-1 ), but not in the low light intensity conditions. Total photosynthetic capacity in Chinese cabbages grown under 800 μ mol·m-2 ·s-1 increased due to the greater leaf area of the plants, even though the photosynthetic rate was lower than that measured under 1,000 μmol·m-2 ·s-1 . In addition, the values of Fv/Fm indicated that Chinese cabbage was mildly stressed under 1,000 μmol·m-2 ·s-1 . We recommend a light intensity of 800 μmol·m-2 ·s-1 for the production of high-quality Chinese cabbage. We hope that this study can help emphasize the importance of light intensity when maximizing the economic benefits of Chinese cabbage.