| Faber Cymbidium is a perennial herbaceous plant.It has very high values in commerce and ornament.Orchid propagation generally depends on offshoot,so the velocity is slow and the propagation coefficient is low.In addition,orchid seeds have no endosperms and cotyledons, therefore they can't germinate generally.Besides,Cross breeding is the main method in orchid breeding which is time-consuming and tedious because of the seed hypoplasia.Accordingly, propagation and breeding are the main problems of the orchid.Up to now,studies on the orchid mainly concentrate on Foreign Orchids and Chinese Cymbidium of Chinese Orchids,few on Faber Cymbidium.Proper breeding method was expected to obtain for rapid propagation and genus improvement through the study on technology and method based on tissue culture and polyploidy breeding.Therefore,the experiment made a research on polyploidy induction in tissue culture,in order to creat new genus and lay the foundation of polyploidy breeding of Faber Cymbidium.The result in the culture in vitro regeneration of Faber Cymbidium showed:The explants were dipped in the scour 10 minutes and washed 30 min by tap water,then sterilized 60 seconds by 75% alcohol and 10 min by 0.1%HgCl2,rinsed 4～6 times by sterilized water.The appropriate medium for inducing buds from explants was MS+1.5 mg/L6-BA+0.2 mg/LNAA,induction rate was 93.3%; The best of multiplication medium for Faber Cymbidium was MS+1.0 mg/L6-BA+0.1 mg/LNAA, multiplication coefficient reached 4.8;the best rooting medium was MS,the states of plantlets and roots were good,the induction rate was 100%.The surviving rate of plantlets was 85%after transplanted to the ground.On the base of building the system of regeneration in vitro,the inducing tetraploids of the Faber Cymbidium was done by the solution of colchicines.The methods were adapted:marinating and composite culture.The result showed:the marinating was a better method.The autotetraploids were induced by immersed the stems with buds in 0.5%colchicines solution for 48 hours.The induced plantlet was identified by the number of the chromosome.The number of the chromosome was 2n=4x=88,belonging to tetraploids plants.The highest rate of inducing was 13.3%.Tetraploid Faber Cymbidium had a good multiplication effect,which cultivated on the best mediums for diploid plant. The optimal medium for rooting was MS+1.0 mg/LIBA.The states of multiplication and rooting were good.The surviving rate of tetraploid plantlets was 60%.Plant morphology and cytology observation on two ploidy of Faber Cymbidium with similar growth stage and environment background suggested that tetraploids were bigger than diploids in the leaf morphology.The thickness and width of the leaves of tetraploids were bigger than the diploids.The thickness of tetraploids was 185.7%that of diploids.The width was 143.7%that of the diploids.The length turned shorter and the leaf index became smaller,were 83.5%and 58.1%those of the diploids respectively.By the analysis,those indexes were significantly different.The leaves of tetraploids were thicker,the plants were stronger and the roots of tetraploids were fatter.Comparing the characteristic of the tetraploids stomas with that of diploids,the result showed:the density was evidently decrease,was 55.2%that of diploids.The guard cells of the tetraploids obviously augment. The length and width of tetraploids were 146.5%and 140.5%of those of the diploids respectively. The number of chloroplasts in the guard cells increased evidently and was 142.6%of the diploids. The stomas of the tetraploids became bigger,the length and width of tetraploids stomas were 157.6% and 128.4%of those of the diploids respectively.By the analysis,those indexes were notably different.So leaf thickness,leaf width,stoma density,guard cell size,chloroplast number can be used to identify tetraploid and diploid of Faber Cymbidium..The tetraploid and diploid plantlets of Faber Cymbidium were carried out the low-temperature treatment,then their exosmosis rates of electrolyte and rates of damage of cytomembrane were compared.Under the same temperature,the electrolyte exosmosis rate and damage of cytomembrane of tetraploid plants were lower than the diploid ones.The result indicated that the cold resistance and drought of the tetraploid were both stronger than diploid,it has fully manifested the superiority of polyploidy.Additionally,the mensurate result found that,chlorophyll content was increasing along with the ploidy.This result can provide important data for planting and breeds selectively. |
