Objective This study aimed to explore the flowering biological characteristics and breeding system of Camellia meiocarpa, thereby providing a reference for the germplasm innovation and cultivation of C. meiocarpa.

Method Based on the three superior clones of C. meiocarpa TRCM-1, TRCM-3 and TRCM-7, the flowering phenology and floral organ characteristics of C. meiocarpa were observed by field investigation method, the stigma receptivity was determined by benzidine-hydrogen peroxide method, the pollen morphology was observed by scanning electron microscope, and the breeding system was analyzed by pollen/ovule ratio (P / O) and out-crossing index (OCI).

Result The flowering period of C. meiocarpa extended from mid-October to late December, with a total duration of 42～50 d. Significant differences in floral organ characteristics were observed among the three clones: TRCM-1 exhibited the highest number of stamens, TRCM-3 showed the smallest difference between pistil and stamen heights, and TRCM-7 had the largest petal length, petal width, and corolla diameter. Stigma receptivity lasted for 9～10 days, beginning 2～3 d before anthesis, and peaking 1～4 d after flowering. In TRCM-1 and TRCM-3, stigma receptivity was maintained for up to10 days. Among the three clones, TRCM-3 exhibited the highest pollen viability, while no significant difference in pollen tube length was detected. Pollen grains were oblong-spherical, with a trilobate circular shape in polar view and nearly circular or oblong in equatorial view. The out-crossing index (OCI) of C. meiocarpa was 4, and the pollen/ovule ratio (P / O) ranged from 77 604 to 139 424, indicating an obligate outcrossing breeding system that requires pollinators.

Conclusion There are obvious differences in the flowering biological characteristics and breeding systems of the three superior clones of C. meiocarpa, which can provide a reference for the germplasm innovation of C. meiocarpa.