Abstract
Light is the main source of energy for plants, and Solanum betaceum is a typical economic crop that can grow and develop without too much light intensity. To investigate the growth status of Solanum betaceum seedlings under low light conditions and provide a theoretical basis for cultivating efficient Solanum betaceum seedlings. This study used Solanum betaceum seedlings as materials and set up four shading levels: full light (0% shading), mild shading (25% shading), moderate shading (50% shading), and severe shading (75% shading). We measured the contents of carbon(C), nitrogen(N), phosphorus(P), soluble sugars, starch, and Non-structural carbohydrates(NSC) in plants, as well as the photosynthetic physiological characteristics (fluorescence parameters, photosynthesis parameters, and photosynthetic pigment content) and root characteristics (root length, root surface area, root volume, and average root diameter). Our research results indicate that with the increase of shading intensity, the C, N, P content, and NSC content in various organs of Solanum betaceum seedlings show a significant change pattern of first increasing and then decreasing (P < 0.05). The C, N, and P content of plants is highest under 25% shading, while the NSC content of roots, stems, and leaves are highest under 50% shading treatment. Photosynthetic pigment content, chlorophyll fluorescence parameters, net photosynthetic rate (Pn), stomatal conductance (Gs), transpiration rate (Tr), and intercellular carbon dioxide concentration (Ci) all reached their maximum under 50% shading treatment; whereas root morphology is best under 25% shading treatment. In summary, under 25%~50% shading treatment, the photosynthetic system structure of Solanum betaceum seedlings is more complete, energy metabolism is faster, light energy conversion efficiency is higher, light energy absorption and utilization are better, nutrient synthesis is more suitable for the growth and development of Solanum betaceum seedlings, while excessive shading inhibits seedling growth and development.