Study On Flowering Biological Characteristics Of Barnardia Japonica

To exploring the flowering biological characteristics of Barnardia japonica,flower bud differentiation and development process,comprehensive characteristics of flower and breeding system,flowering phenology and its pollination mechanism were studied,taking Barnardia japonica introduced from Changbai Mountain to the nursery of College of Landscape Architecture in Northeast Forestry University were used as materials.The results showed:The process of flower bud differentiation of Barnardia japonica can be divided into seven stages which included undifferentiated period,the differentiation period of inflorescence primordium,the differentiation period of bracts primordium,the differentiation period of flowers primordium,the differentiation period of tepals primordium,the differentiation period of stamens primordium and the differentiation period of pistil primordium.Flower bud differentiation began in late April and it take about 30 days to complete morphological differentiation,followed by the development of floral organs.There were four rooms anthers of Barnardia japonica.The anther wall consisted of five layers of cells that included epidermis,endothecium,middle layer(2 layers)and tapetum.When the two-cell pollen was mature,the anther wall was only a double-layer structure composed of epidermis and endothecium.The development of the anther wall belonged to a dicotyledonous type and the tapetum belonged to the glandular tapetum type.Cytokinesis in the microsporocyte meiosis was continuous which produced two kinds of tetrads,type of symmetrical and type of tetrahedral.The mature pollen of Barnardia japonica was two-cell type.The ovary with 3 carpels and 3 rooms has axile placenta,anatropous ovule,thick nucellus and bitegmic.The development of embryo sac is Endymion type.The individual flower longevity was 4~5 days and individual inflorescence duration was 9~28d.Inflorescences each with 40~300 flower buds opened from lower to upper.In the process of flowering,the percentages of open flowers showed a single peak change,and the peak of individual plants appeared in 5~9 days.Floral display also showed a significant singlepeak trend and the largest day appears in 8~11 days.Anthers who could basically drained pollen began to crack after they were exposed to the air 20~40min.The optimum culture medium for the pollen of Barnardia japonica was 10g·L-1sucrose+0.3g·L-1H3BO3+0.2g·L-1Ca(NO3)2.The Pollen viability was about 80% in early flowering season and peak flowering season,but at the end of the flowering period it dropped to about 20%.Stigmas had the ability to grant before or after anthers loose powder and stigma receptivity was strongest after flowering 1~2ds.The results showed that the outcrossing index was 4 and the pollen-ovule ratio was 3111.Combined with the results of bagging test,the breeding system of Barnardia japonica can be determined as outcrossing,partially self-compatible and needed pollinators during pollination.The population flowering of Barnardia japonica was from mid to late July to mid to late August,the population flowering duration is 31~35d.There was a significant positive correlation between the flowering number per plant and fruit number and length of florescence(p<0.01)and a significant correlation between the length of florescence and fruit number(p<0.05).However,there was no correlation between flowering time and flowering number,fruit number and length of florescence.In other words,the more the number of flowers,the higher the fruit rate and the longer the flowering period.There were 14 species of flower visitors that belonged to 5 orders and 10 families,of which 5 families and 10 species were pollination insects.The main pollination insects were Syritta pipiens,short-tailed tube aphid,Episyrphus balteatus,Volucella nigricans,and Eumenidae insect of Hymenopterous.Volucella nigricans had the longest retention time on single flower,usually above 1 min.On the frequency of flower visiting,Syritta pipiens had the highest frequency of visiting and the short-tailed tube aphid was the next.There were significant differences in the frequency of day visit between witn different pollination insects.The visiting time of Syritta pipiens was 7: 00 ~ 17: 00,mainly in the morning.And the visiting time of the short-tail tube flies through the flowering time,focusing on the noon.In general,nsects of Syrphidae played a more important role in pollination than other insects.