Correlation analysis of light intensity and growth, photosynthetic pigment, color value of Betaphycus gelatinae

We investigated the growth, photosynthetic pigment and color change of Betaphycus gelatinae at different light intensities (1 000, 3 000, 5 000, 7 000 and 9 000 lx). Based on CSE-1 imaging chromaticity detection and analysis, we studied the correlation of color parameter L^*a^*b^*(CIE 1976) with light intensity, growth and photosynthetic pigment. The results show that the relative growth rate and weight gain rate increased significantly with the increase of light intensity. The suitable light intensity for growth was 7 000−9000 lx. However, when the light intensity was 1 000 lx, there was no obvious growth of B. gelatinae. With the increase of light intensity, the contents of chlorophyll a, carotenoids, phycoerythrin and phycocyanin generally decreased, and the color of B. gelatinae gradually changed from reddish brown to green. The tristimulus values (XYZ) showed a significant distribution difference on the CIE 1931 chromaticity diagram at different light intensities. Light intensity was significantly positively correlated with lightness L^*(P<0.05), but significantly negatively correlated with red-green value a^*(P<0.01). There was a significant positive correlation between relative growth rate with lightness L^* and yellow-blue value b^*(P<0.05). Chlorophyll a was significantly negatively correlated with lightness L^*(P<0.05), but significantly positively correlated with red-green value a^*(P<0.05). Both phycoerythrin and phycocyanin were significantly positively correlated with the red-green value a^*(P<0.05).