Effect Of Pollination,fertilization And Embryo Development On Seed Setting Of Dianthus Hybridus

Dianthus is an important ornamental plant resource,and among them,Dianthus hybridus is a perennial herbaceous plant,which is Widely used in landscaping practice,mainly based on F1 generation seed breeding.The low seed setting rate,Less seed formation in seed pods and the quality of seeds is lower are the main drawbacks in the hybrid seed production process.The breeding practice demonstrated that seed formation process are closely related to the pollination,fertilization and embryo development,Therefore,Dianthus hybridus was used as the testing material in this investigation,the benzidine-H2O2 method was utilized to test stigma receptivity,scanning electron microscopic and fluorescence microscopy were used to observe the morphology of male parent pollen and maternal stigma,paraffin section and whole ovary stain clearing technique were used to observe pollination,fertilization and embryo development,and the results were arranged by statistical analysis method.The seed growth and seed germination rate were investigated.Exploration of the effects of pollination and embryo development on seed formation,which was regarded as the theoretical basis for hybrid seed production and the foundation for further breeding investigation.The results are presented as follows:1.In artificial cultivation conditions,Parent show early flowering period at the end of April every year,flowering period at the beginning of May,for seed harvesting period at beginning of June to mid of June,and the blooming time will last for about 10 days and the whole cross pollination process will last for about 15 days.Pollen germination was test in vitro,and the most suitable condition is 10 % sucrose with 0.2 % boric acid and 0.02 %Ca Cl2 and pollen viability was up to 39.16% in the vitro culture.2.Morphology investigation found that there were a abundant of malformed pollen grains,the stigma of female parent is "dry" stigma,the surface has a large number of finger-like of the papillae with different thickness,and when the stigma grow to "Y" and "Y-shape horn",the finger-like mastoid will fully grow and developed,which is suitable for pollen attachment,stigma implantation,identification,germination of pollen grains.The result of benzidine-H2O2 shows that stigma shows grantable within period of flowering from 4th to8 th,and stigma receptivity became stronger in the first 5th to 7th days and strongest at the6 th day,and morphology in this period is "Y-shape horn".3.Fluorescence microscopy observation indicated that pollen tube growth into embryo sac was hindered and pollen tube entered into the embryo sac and spirally growth which failed to release the contents,leading to the fertilization failure of the ovules.Paraffin section method combined with the overall transparency method were utilized to observe the results of fertilization and embryonic development,indicated that normal embryonic development underwent embryos period,globular embryos period,rod shaped embryos period,heart shaped embryos period,torpedo shaped embryos period,and cotyledon embryos period;Ovules were not fertilized,bipolar nucleus was not fused,free endosperm free nucleus only existed in embryo sac,disintegration of spherical embryo,resulting in the ovules failed to form seeds or formed the abortion seeds,the final seed setting rate achieved was 55.57%,seed setting rate was 63.12%,seed germination rate was 68.13%.4.The stigma receptivity in different periods after flowering was investigated in this study,suitable pollination period was clearly determined to provide reference for pollination of seed production.The observation of fertilization and embryonic development process indicated that fertilization failure of the embryo and fertilized abnormalities and disintegration of spherical embryo were the main reasons leading to low seed setting rate,which was set the foundation for improving the seed setting rate and breeding work in the near furture.