Flowering characteristics and breeding system of Rhododendron siderophyllum.
The flower phenology and flower-visiting insects of Rhododendron siderophyllum population were investigated and studied, and the flowering characteristics was analyzed. Through regulating outcrossing index, pollen-ovule ratio and artificial pollination, the reproductive system of Rhododendron siderophyllum was studied. The results showed that Rhododendron siderophyllum flowered from the beginning of February to July, the flowering span of individual flower, single flower truss and plant were 7.06±2.74 d, 12.33±2.37 d and 16.17±4.24 d respectively. The pollens and the pistil matured at the same time at anthesis, but the time of the most vigourous was different. The best pollen vigour was the first day at anthesis and the best pistil receptivity was from the fourth to sixth day at anthesis. The breeding system of Rhododendron siderophyllum was outcrossing with self-compatibility, pollinators were necessary. Geitonogamy was the dominant pollinated method. Bees were the main effective pollinators of Rhododendron siderophyllum. However, weevil beetles, ants and sawflies were invasive insects, seriously affected its pollination. The low frequency of pollinator visiting might be the main reason of the low natural hybrid seed setting rate.