Red light optimized physiological traits and enhanced the growth of ramie (Boehmeria nivea L.)

Light is an important variable affecting the plant growth. In present study, the effects of different color light-emitting diodes (mixed colors, red, blue, and orange light) on plant growth, gas exchange, and oxidative stress were investigated in Boehmeria nivea L., by means of measuring growth, photosynthesis, chlorophyll (Chl) content, reactive oxygen species (ROS), and activity of antioxidant enzymes under controlled conditions. Comparing to the mixed colors light, red light significantly increased shoot and leaf biomass, plant height, number of leaves per plant, and stem diameter by increasing the Chl content and therefore promoting the highest photosynthetic capacity. This might partially be explained by the decrease of malondialdehyde and proline contents as well as the activities of superoxide dismutase and peroxidase under red light, to keep a better internal environment of the cell. However, blue and orange light decreased plant growth, and increased the activities of antioxidant enzymes which suggest an environmental stress on plants. These results suggest that red light can enhance B. nivea growth by activating photosynthesis and reducing ROS accumulation.