Abstract:Laminaria hyperborea is an important commercial seaweed, which has great potential for seaweed bed construction and artificial cultivation in China. To verify the suitable light for the growth of L. hyperborea young seedlings and clarify the biochemical response mechanism under light stress, the relative growth rate and biochemical responses under different light intensities were studied. Under these experimental conditions, the main conclusions are as follows: Light was beneficial for the growth of L. hyperborea young seedlings in the range of 40~80 μmol photons/(m2·s). The relative growth rate showed significant negative interrelation with the content of malondialdehyde (MDA), which indicates that membrane lipid peroxidation may be one of the reasons contributing to the low relative growth rate of L. hyperborea young seedlings. An extremely significant positive correlation was found between the content of superoxide anion (SA) and the content of MDA of L. hyperborea young seedlings. The specific activity of superoxide dismutase (SOD) and catalase (CAT) were negatively correlated with the content of SA and MDA, respectively. And the negative relationship between the specific activity of CAT and the content of SA was significant. Moreover, an extremely significant and positive correlation was found between specific activity of peroxidase (POD) and SOD. It can be inferred from the above correlation analysis results that SOD, CAT and POD play important roles in removing reactive oxygen species (ROS) and there is a significant synergy between SOD and POD in L. hyperborea young seedlings. The light stress environment was not conducive to the accumulation of soluble protein resulting in the accumulation of MDA in L. hyperborea young seedlings, which indicates that the total metabolic level was reduced and the ROS level was increased in this environment. The content of carotenoid and the specific activity of SOD and POD in L. hyperborea young seedlings will increase so that the ROS level can be reduced under high light stress, thus relieving light oxidative damage. The content of chlorophyll-a of L. hyperborea young seedlings will increase so that it can capture the limited light energy more effectively under low light stress. However, the antioxidant enzyme activity was significantly decreased as a result that led to a serious imbalance of ROS metabolism under low light stress, which resulted in more severe membrane lipid peroxidation damage. These results can provide the theoretical basis for the artificial breeding and cultivation of L. hyperborea in the future.
