PHOTOSYNTHETIC CHARACTERISTICS OF LARIX GMELINII SEEDLINGS UNDER DIFFERENT LIGHT INTENSITY

. To explore the effects of different light intensities on the physiological growth of Larix gmelinii seedlings, this study assessed three height grades of L. gmelinii seedlings (≤0.5–1, 0.5–1, and 1-3 m) under the following treatments: full light (control), 65% NS (natural sunshine), 35% NS, and 10% NS. After treatment, photosynthetic pigment content, light response curve, CO 2 response curve, Chlorophyll Fluorescence and Diurnal Variations in Photosynthesis were assessed. Shading increased the photosynthetic pigment contents of L. gmelinii seedlings and young trees and played a positive role in the adaptation of L. gmelinii seedlings and young trees to low-light environments. The maximum net photosynthetic rate, maximum carboxylation rate, maximum photoelectron transmission rate, and utilization efficiency of acetone phosphate of L. gmelinii (1–3 m) considerably increased under the 65% NS treatment, showed the strongest photoinhibition resistance and a high proportion of the open PSII reaction center. The best shade treatment for young L. gmelinii trees at 1–3 m was 65% NS, which indicates that this treatment can improve the photosynthetic capacity of young L. gmelinii trees. However, for the growth of smaller L. gmelinii seedlings, an environment with greater light intensity is more suitable.