Breeding system of Orchidantha chinensis var.longisepala

Plant flowering and breeding systems are important for understanding plant population reproduction.Field observation,outcrossing index (OCI),pollen-ovule ratio (P/O),and hand pollination were adopted to study the breeding system of Orchidantha chinensis var.longisepala(D.Fang) T.L.Wu.Paraffin sections and scanning electron microscopy were used to observe the structure and morphology of the stigma and viscidium.Results showed that the average flowering phenology duration of O.chinensis var.longisepala was 18 d and floral development was divided into five stages based on flower morphology:(1) bud swelling;(2) before sepal retroflex;(3) sepal retroflex;(4) labellum withering;and (5) sepal withering.Furthermore,results showed that the OCI value was 4,the P/O ratio was 253.89 ±21.09,and the seed setting rate of cross pollination on the stigma was 45%(2014) and 75%(2015).Based on the above results,the breeding system of this species is xenogamy and requires pollinators.Paraffin sectioning showed smooth epidermal cells between the viscidium and receptive areas of the stigma.Furthermore,hand pollination and determination of sugar content of the secretions showed that the viscidium was without receptivity.The function of this viscidium might be the production of a sticky secretion to enable the pollen masses to adhere directly to the backs of pollinators.We concluded that the lack of effective pollinators was due to poor weather and the low synchrony index of flowering.The main factors for its restrictive distribution were asexual propagation with rhizomes when sexual propagation was limited.