Histological Research Of Somatic Embryogenesis And Development In Two Lily Species Native To China

Somatic embryogenesis is of great significance for breeding,germplasm conservation and genetic improvement.Current researches focus mainly on effective of plant growth regulation and mediums on somatic embryo inducement.Most of which only examined the somatic embryogenesis depending on appearence by the naked eye,but rarely involved in essencial histological examination,especially for histological analysis during the transformation stage from somatic cells to embryogenic cells.The study on morphogenesis in Lilium is limited by lacking of histological examination.Using cell biology techniques,this study focused on origin patterns during somatic embryogenesis in Lilium davidii var.unicdor and Lilium pumilum DC.Fisch,with the desire to lay foundation for elucidating the mechanism of somatic embryogenesis in Lilium.The results are presented as follows:1.The origin of somatic embryoSomatic embryos were originated via both the exogenous and the endogenous origin in L.davidii var.unicdor.and L.pumilum DC.Fisch..The exogenous origin pattern accounted for 91.45%and 83.85%in davidii var.unicdor and L.pumilum DC.Fisch.,respectively.The initially cell divisions of embryogenic cells occurred on the 9th day after cultured in mediums.In exogenous origin pattern,somatic embryos developed from superficial cells or sub-superficial cells.Endogenous origin patterns were observed on the 12th and 15th day in L.davidii var.unicdor and L.pumilum DC.Fisch.,respectively.There were two patterns of endogenous origin in L.pumilum DC.Fisch..Vessels were observed in both the two origin patterns.Somatic embryos of both lilies developed from multicellular cells and should be considered as indirect regeneration,which means it regenerated to somatic embryos after dedifferentiation and differentiation through embryogenic callus.2.Differences of indicators during somatic embryogenesisThe duration of embryogenic callus in both lilies was different.It needs 42 d and 28 d for embryogenic callus formation in L.pumilum DC.Fisch.and L.davidii var.unicdor,respectively.The initially anticlinal division and periclinal division occurred on the 9th day and 15th day in L.davidii var.unicdor and L.pumilum DC.Fisch.,respectively.The protoderm were observed on the 24th day and 30th day in L.davidii var.unicdor and L.pumilum DC.Fisch.,respectively.Vessels were observed in torpedo-shape embryos and globular embryos.In addition,on the 30th and 33rd day,physiological isolation were observed in L.davidii var.unicdor and L.pumilum DC.Fisch,respectively.3.Changes of starch granules in the development of somatic embryosAfter cultured 9 d,large quantities of starch grains concentrated in embryogenic cells,suggesting the first accumulation of starch.Followed,it appeared in globular embryo and early torpedo-shape embryos for the second and third accumulation of starch.Finally,it decreased along the development.4.Ductal cells during somatic embryogenesisIn the process of somatic embryogenesis,ductal cells occurred along with embryonic cell division.In the late stage of somatic embryogenesis,ductal cells formed a straight line.