Studies On The Somatic Embryogenesis Of Liriodendron Hybrids (L.Chinense (Hemsl.)Sarg.Xl.Tulipifera L.)

Somatic embryogenesis was successfully done in Liriodendron hybrids with the immature zygotic embryos as explants. Some factors had been tested about their effects on somatic embryogenesis in this research, such as genotype, developmental stage ,culture condition ,plant growth regulator and osmotic potential. The results showed that the embryogenic callus was successfully induced when the experimental materials were cultured on 1/2 medium supplemented with 2,4-D 2.0³.0 mg · L^-1. Sucrose can be used as osmoticant to improve osmotic potential of the medium and it was effective for somatic embryogenesis. The induction of somatic embryos was best when the embryonic callus was cultured on MS medium supplemented with 1.0 ⁴.0 mg · L^-1ZT. It was also proved that a proper amount of ABA can lessen the production of abnormal embryos. In addition, the genotype , developmental stage of immature embryos and light condition were important to somatic embryogenesis.Histological study on the origin and development of somatic embryos, it was found that somatic embryos were mostly developed from single embryogenic cells that possessed the ability of embryoid occurrence from the surface of the callus. At the early development stages , the proembryos were limited in a boundary of thick cell wall. Plantlet regenerations were developed from global embryo, heart-shaped embryo, torpedo-shaped embryo and cotyledon embryo, in which the V-shaped vessel vascular bundles and shoot tip meristem and root tip meristem were observed. By means of transmission scanning electron microscopy and scanning electron microscopy technique, it was found that the structure of embryogenic cells were regular and organelle were comparatively abundant . At the same time , we found that embryogenic cell metabolism were vigorous by studying the difference between embryogenic callus and nonembryogenic callus. ATPase activity was observed on the membrane system of the embryogenic cells.The genetic stability of the plantlets regeneration has been studied by counting the chromosomes and it was found that these plants were diploid mostly, while one of the clones and its regenerated plants all were tetraploid.