Effects of Red and Blue Light Ratio on Growth and Endogenous Hormone Synthesis of Tsoongiodendron odorum Seedlings

Taking 2-month-old seedlings of Tsoongiodendron odendron as experimental materials, the seedlings were treated with red and blue monochromatic LED(light emitting diode) lights and composite LED lights. The experiment lasted for 120 days with pure white light as control. The seedling height, ground diameter, biomass and the content of GA₃, ABA, IAA, ZR were measured under different light quality. The findings indicated that the growth of seedling height and ground diameter was the highest under pure blue light treatment and the lowest under pure red light treatment, and the growth of seedling height and ground diameter increased significantly with the increase of blue light ratio in compound light; the dry matter accumulation of roots, stems and leaves and the total dry weight of seedlings reached the highest value under the pure blue light and the compound light with the highest proportion of blue light, and the lowest value under the compound light with the highest proportion of red light and pure red light; the content of GA₃ and ZR were higher under pure blue light treatment, while the content of ABA was the highest under pure red light treatment. Adding the appropriate proportion of blue light to pure red light was conducive to reduce the synthesis of ABA, and promote the growth and development of seedlings; the best comprehensive quality of seedlings appeared under pure blue light treatment, and with the increase of the proportion of blue light, the quality of seedlings showed a better trend. In summary, pure blue light treatment had the best growth promoting effect, which could increase the dry matter accumulation, improve the seedling quality and growth rate; red light could promote the synthesis of ABA in leaves and inhibit the growth of seedlings. Although the H/D and SQI under pure blue light treatment were the highest, the appropriate proportion of red and blue light combined with irradiation of seedlings could better regulate the balance between endogenous hormones in seedlings, which was more conducive to improve the comprehensive quality of seedlings, shorten the cultivation period, and cultivate high-quality seedlings more efficiently.