Li Lu

Cycas is one of the most ancient extant seed plant lineages on Earth, with a fossil record and evolutionary history dating back to the Carboniferous period. In this study, six screened SSR primer pairs were used to analyze the genetic diversity and population structure of 640 samples from 41 populations representing eight Cycas species collected from Guangxi, with the aim of providing a theoretical basis for the conservation of wild cycad resources in this region. The results showed that the average number of alleles (Na) across the eight species ranged from 1.945 to 3.643, the average effective number of alleles (Ne) ranged from 1.548 to 2.245, Shannon’s information index (I) ranged from 0.446 to 0.824, observed heterozygosity (Ho) ranged from 0.222 to 0.453, and expected heterozygosity (He) ranged from 0.293 to 0.443, indicating a moderate overall level of genetic diversity. Among the species, C. sexseminifera exhibited the highest genetic diversity (I = 0.824, He = 0.443), whereas C. guizhouensis showed the lowest (I = 0.446, He = 0.293). In addition, the interspecific genetic differentiation coefficient (F_st) ranged from 0.047 to 0.354, and gene flow (N_m) ranged from 0.456 to 5.094. Except for C. guizhouensis, relatively high levels of gene flow were detected among species. Principal Coordinates Analysis (PCoA) revealed that the 640 samples could be divided into three genetic clusters, which were not strictly consistent with species boundaries. AMOVA further indicated that 78% of the total genetic variation was distributed within populations, including 60% within individuals and 18% among individuals within populations. These findings provide important insights into the genetic diversity and differentiation patterns of Cycas species distributed in Guangxi and offer a theoretical foundation for their introduction, ex situ conservation, and scientific management of genetic resources.

This study investigated two Ormosia species, Ormosia henryi and Ormosia hosiei, to examine their adaptive mechanisms to varying light conditions. Four light intensity treatments were applied to measure their growth parameters, photosynthetic characteristics, leaf microstructure, and chlorophyll content. The results showed that (1) both Ormosia species exhibited significant variations in functional traits under different light conditions. Growth parameters displayed high plasticity, and photosynthetic traits and leaf structural characteristics were optimal under 50% light intensity. (2) The overall phenotypic plasticity of O. henryi and O. hosiei was similar, though differences were observed in the plasticity of PT, SD, and Chl b, indicating distinct strategies in response to environmental changes. (3) Most functional traits were significantly correlated, and their coordinated changes contributed to the formation of adaptive capacity to light variation in both species. (4) During the seedling propagation of Ormosia species, approximately 50% shading should be applied. In conclusion, this study reveals the variation and adaptive mechanisms of functional traits in Ormosia seedlings under different light intensities, providing a theoretical basis for understory light environment management and shade cultivation, as well as a reference for further studies on the light ecological strategies and shade tolerance mechanisms of Ormosia species.

This study investigates the differences in photosynthetic characteristics of Paphiopedilum parishii (Rchb.f.) Stein during its reproductive and nutrient growth periods. Using plants from the same individual, we compared light response curves, chlorophyll content, leaf epidermal structure, and leaf anatomical structure between these two growth stages. The results show the following: (1) The overall shape of the light response curves was similar across both periods, but plants in the nutrient growth period exhibited higher net photosynthetic rates (P_n) at all light intensities compared to those in the reproductive growth period. (2) During the nutrient growth period, apparent quantum efficiency (AQY), maximum net photosynthetic rate (P_max), and light saturation point (LSP) were all significantly higher than in the reproductive growth period, while the light compensation point (LCP) and dark respiration rate (Rd) showed no significant differences. (3) Structurally, during the nutrient growth period, stomatal density significantly increased, while stomatal area decreased. Additionally, leaf thickness and mesophyll tissue thickness both markedly increased, indicating enhanced carbon assimilation efficiency through improved CO₂ uptake capacity and expanded photosynthetic area. (4) Significant differences in leaf anatomical structure between the two periods were primarily observed in leaf thickness and mesophyll tissue thickness, providing more space for energy accumulation during the post-flowering recovery phase. This study systematically reveals the dynamic changes in photosynthetic physiology and structural characteristics of P. parishii across different phenological stages, offering a theoretical foundation for its reintroduction and cultivation management.