论文部分内容阅读
Somatic embryogenesis is an attractive method for mass propagation of superior clones in plantation.However, the major limitations in somatic embryogenesis on commercial applications in many pine species are the low induction rate of embryogenic tissues and the limited subculture times in proliferation.This study had showed the pattems during somatic embryogenesis in Masson pine (Pinus massoniana.).To improve the embryogenic tissues induction rate we tested different development stages of immature zygotic with eight collection dates in 2011 and a relative high frequency of initiation was achived.The most responsive stages were from early cleavage polyembryony to pre-cotyledonary stage.The macroscopic and microscopic observations were done with the embryogenic and no-embryogenic tissues initiated from the megagametophytes containing immatured zygotic embryos.We identified six types of the tissues obtained in initiation and descripted some processes in somatic embryos formation and development during proliferation and maturation, then elucidated the developmental pathway of somatic embryogenesis in Masson pine.Some explants exhibited proliferation of mucilaginous, translucent white masses and had numerous filamentous bumps on the surface.The microscope observations showed that the tissues contained well-developed bipolar structures with distinct embryonal heads and suspensors, in which the small, densely cytoplasmic cells composed the embryonic head whereas the elongated ceils with large vacuoles formed the suspensor apparatus.The tissues, which could be mass proliferated rapidly in subculture and be matured in maturation, were often observed as embryogenic tissues that the aggregates with regular outline and the suspensor cells arranged into bundles.There were some relevance feedback with a series of characteristic stages distinguished by cellular organization and cell numbers (stages of PEM Ⅰ ,PEM Ⅱ, PEMⅢ and early somatic embryo prossessing embryonal mass) during proliferation under limited subculture times.Based on microscopic inspection, we also found the development pathways of the Masson pine somatic embryos formation during proliferation and somatic embryos development in maturation.It is the first time to reveal the patterns during somatic embryogenesis in Masson pine and to provide some baseline information in somatic embryogenesis in coniferous clonal propagation.