| To reveal the potential application and value of biochar in millet cultivation, the Setaria italica variety, Xianggu 3, was planted in the soil pots with three biochar rates (10, 50, and 90 g·kg-1) were supplemented. The seedlings biomass, the morphology of underground roots,aboveground, and the photosynthetic characteristics of millet seedlings were analyzed after sowing 30 days. The results showed that compared with the untreated control (BC0), the different doses of biochar significantly promoted the aboveground and underground biomass and phenotype indicators of millet seedlings, as well as other photosynthetic parameters except the intercellular CO2 concentration. And the effect of 50 g·kg-1 biochar treatment on growth and photosythesis of millet was most obious. Compared with the control (0 g·kg-1), the fresh weight and the dry weight of both the aboveground and the underground were significantly promoted to 220% and 181%, 500% and 350%, respectively, and the root\|shoot ratio increased by 41.7%. The 5 phenotype indicators of the underground, including the root length, the total root length, the total root surface area, the root tip number, and the branch number increased by 124%, 215%, 323%, 86.4%, and 279%, respectively. While the 3 phenotype indexes of the aboveground, including the seedling height, the stem diameter, and the leaf area increased by 48.28%, 50%, and 159%, respectively. The photosynthetic indicators, for example, the leaf relative chlorophyll content and the net photosynthetic rate increased by 21.01% and 167%, respectively. These results suggested that the biochar addition in soil could promote the biomass of millet seedlings through improving the phenotype construction of the underground roots and the aboveground stems and leaves, and enhancing the photosynthetic capacity of leaves. This can lay a foundation for the formation of later crop yield. |