Study On Embryo Development And Non-symbiotic Germination Of Cymbidium Tortisepalum Var. Longibracteatum

Cymbidium.tortisepalum var.longibracteatum is an authentic"Chuanlan"with important ornamental value and genetic resource value,but the seed germination of C.tortisepalum var.longibracteatum is a biological bottleneck which restricting the reproduction of it,and its germination mechanism and conditions are not clear.In this experiment,C.tortisepalum var.longibracteatum was used as the material.The fruit development and anatomical characteristics,embryo development and seed formation,seed germination pathways and non-symbiotic germination conditions were studied.The main results are as follows:1.The fruit development of C.tortisepalum var.longibracteatum showed as a"double S"curve,after pollination,0-40d was the first fast growth period,40-50d was the first slow growth period,50-80d was the second fast growth period and 80-150d was the second slow growth period,and the vertical and horizontal diameters of the mature capsule were about74.84mm and 16.12mm,respectively.The capsule was divided into six valves,three of which had a"V"-shaped placenta,which were fertile,and three valves without a placenta,which were infertile.The weight of single seed was about 3.92±0.40?g,and the seed content in a capsule was bout 37.98±3.71×10~4.2.The interval between the pollination and fertilization of C.tortisepalum var.longibracteatum was about 60 days.The first unequal division of zygote forms basal cell and terminal cell,basal cells do not participate in the formation of embryo proper and gave rise to a 5-cell suspensor.The suspensor degenerated after seed maturation.Terminal cell gave rise to globular embryos after multiple divisions,and globular embryos did not differentiate when seeds were mature.Development of embryo was solanad type.The seed coat was divided into endopleura and episperm,when the seed matured,endopleura shrinks into a dense membrane that was close to the embryo,air cavity existed between the endopleura and episperm.3.There were two ways of seed germination:One was that the seed embryo first extends to the zygomatic end,and then expanded and broken the seed coat;the other was that the seed embryo swelled from the side perpendicular to the seed coat and broken through the seed coat.Both ways coexisted during germination.After the seed embryo broken through the seed coat,it turned green,and developed into a protocorm,then gave rise to a seedling through the rhizome.There were two intermediate propagules of callus and protocorm-like bodies in the process of seed germination,both of which can achieve plant regeneration through the somatic embryonic development pathway.4.The optimal harvest time for non-symbiotic germination of C.tortisepalum var.longibracteatum seeds were 120d after pollination;the most suitable pretreatment method was to store at 4?for 30 days;The most suitable medium for seed germination was Hyponex medium with 1.0 mg/LGA3,whichy the start-up germination time was 86 days,and the number of germination was the highest,reaching 61.33 per bottle.Adding activated carbon to the medium can promote seed germination,and adding banana juice and potato juice has no promoting effect on seed germination.