Establishment Of Plantlets Regeneration System And Origin, Development Of Intermediate Propagule Of Cymbidium Tortisepalum Var. Longibracteatum

Cymbidium tortisepalum var.Longibracteatum is one of the most beautiful and appreciated plants in Orchidaceae,Cymbidium.Because of its rarity,since the 1980 s,the wild resources of Cymbidium tortisepalum var.Longibracteatum have suffered irrecoverable damage.Solving the problem of large-scale and rapid reproduction of Cymbidium tortisepalum var.Longibracteatum is of great significance for the protection of its genetic resources and industrialized cultivation.In this study,the factors and conditions affecting the proliferation,differentiation and plant regeneration for rhizome formed by the aseptic germination from mature capsule of C.tortisepalum var.longibracteaum has been studied.At the same time,the origin and development of the intermediate propagules of C.tortisepalum var.Longibracteatum were studied from the level of histocytology.The main research results are as follows:1.The basic medium,exogenous plant hormones,natural additives,cutting methods and culture methods have important effects on the proliferation of rhizome of Cymbidium tortisepalum var.Longibracteatum.The optimal medium for the proliferation is 1/2MS +NAA0.5mg/L+6-BA1.0mg/L+banana juice 3%.The liquid-solid alternating culture method can achieve the highest proliferation rate.2.Subculture time,basic medium,culture methods,exogenous plant hormones and activated carbon(AC)affect the differentiation direction of rhizome of Cymbidium tortisepalum var.Longibracteatum towards adventitious buds.The best medium for the differentiation is Hyponex No.1+NAA0.8mg/L+6-BA1.2mg/L.When AC is not added,buds differentiate rapidly in early time,but their growth is inhibited by browning in the later.3.The basic culture medium,exogenous plant hormones and AC play important roles in the regeneration process of Cymbidium tortisepalum var.Longibracteatum plants.Among them,NAA is the most important for rooting of adventitious buds,and the dosage is 1.8mg/L.The best medium is Hyponex No.1+AC3g/L+6-BA0.1mg/L+NAA1.8mg/L.After 30 days culturing,the average root length of adventitious buds can reach to 2-3cm and height will up to 5cm or more.4.In the process of tissue culture,the cytological structure of rhizome is similar to that of root,and consists of a three-layer structure of epidermis,cortex and stele.The lateral cell protuberance occurred in the process of rhizome culture has three main ways to continue development: one is to grow lateral branches and then continue vegetative growth after no cell differentiation;the second is to form meristems and differentiate into buds;the third is to further differentiate to form protocorms and callus.The bud formation process of meristem is based on the tunica-corpus theory.Leaf buttress and leaf primordia appear alternately at the top of the morphology,they eventually form banded leaves.The generation of adventitious roots is through stimulating certain cells in the structure to parietal division.The resulting root primitive cells further elongate to form the root primordium,which then expands to the epidermis and breaks through,and finally forms a complete adventitious root.