Abstract:

Viola philippica is a garden plant with excellent ornamental characteristics， and there are large germplasm resources for this species. V. philippica forms different types of flowers during the growing season. The objective of this study was to determine how this variable florescence phenology affects the breeding system. V. philippica produces two kinds of flowers. In spring， it forms chasmogamous flowers with five petals and five calyxes. These flowers are produced in a mass-flowering pattern in a short period from mid- to late April. The flowers produced in summer and autumn are cleistogamous. They have no petals， and the sepals wrap the female parts and stamens. The cleistogamous flowers are produced in an extended flowering pattern from early May to the beginning of September. The average number of pollen grains per chasmogamous flower was 7053， and the pollen/ovule ratio （P/O） was 173.32-204.49. There were 179.2 pollen grains per cleistogamous flower， and the P/O value was 4.46-5.95. The results show that the breeding system of open flowers is heterozygous， partially compatible， and pollinated， while the closed flowers are fertilized. The style of chasmogamous flowers has a curved structure， and nectaries at the base of the dorsal part of the lower two stamens extend to the base of the petals. Bee pollinators press the stigma by colliding with the style， pushing the stamen arm in a lever motion to pollinate， thus promoting the separation of the appendages. The cleistogamous flowers show strict closed fertilization and do not require pollination. The seed setting rate and seed setting rate per individual plant are significantly higher for plants with cleistogamous flowers than for plants with chasmogamous flowers.

Key words: Viola philippica, flower characteristic, pollination mechanism, mating system