Reproduction System of Osmanthus serrulatus, an Endemic Plant to China

Objective: To reveal the pollen competition in plants of different genders and its competitive mechanism via the exploration of the direction and scope of pollen dispersal of Osmanthus serrulatus, and to investigate the relationship between plaque size and the adaptability of progeny through open-pollination, so as to provide a theoretical and technological basis for further studies of floral evolution, population genetics and conservation strategies of O. serrulatus.Method: O. serrulatus, an androdioecious plant species, was studied through a statistical investigation of the sex of individuals in 24 samples of different O. serrulatus populations collected from Donglashan Valley of Baoxing County in Sichuan Province. Observations and comparisons of pistil morphology, number of pollen grains, and external features of unisexual male individuals and hermaphrodites of O. serrulatus were made; 10 pairs of polymorphic SSR primers were used to analyze 271 candidate male parents and 494 progeny plants of 24 population samples.Result: 1) For O. serrulatus in Donglashan Valley, the ratio of male individuals and hermaphrodites was 1:1. The pistils of the flowers of hermaphrodites developed soundly, while the flowers of unisexual males showed a reduced pistil. 2) Calculation at 80% confidence level was performed for 376 progeny trees (76%) to identify the sole male parent. Of all the progeny trees whose male parents had been identified, respectively 213 and 163 progeny trees were derived from male parents and bisexual parents. 3) The average effective dispersion radius for the pollens of the 24 population samples was 46.35±25.62 m. The mating distance of mother plants showed approximate normal distribution, further indicating outcrossing of the plants. Stocking density, altitude, wind direction and other factors may affect the mating pattern of O. serrulatus.Conclusion: Experiments showed that natural populations of O. serrulatus are functionally androdioecious and self-compatible; and the reproduction system may be a transitional type evolving from hermaphrodite to diclinous. © 2018, Editorial Department of Scientia Silvae Sinicae. All right reserved.