大车前胚乳与胚发育的细胞胚胎学研究

Cytoembryological Studies in the Development of Endosperm and Embryo in Plantago major L.

应用石蜡制片技术研究了大车前胚乳与胚发育过程的细胞胚胎学特征,为车前科胚胎学及分类地位的确立提供相关资料。结果表明:大车前成熟雌配子体为七细胞七核的蓼型。经双受精后形成合子与初生胚乳核。胚乳发育类型为细胞型,初生胚乳核第1次横分裂产生珠孔室与合点室胚乳细胞。珠孔室胚乳细胞经1次纵分裂或2次连续相交的纵分裂形成2个或4个胚乳细胞;进而同步进行横分裂形成2排,即4个或8个胚乳细胞;靠近珠孔的2个或4个胚乳细胞分化并发育成为单核的管状胚乳珠孔吸器;靠近合点室胚乳细胞的2个或4个细胞进行各个方向的分裂形成胚乳本体,并将合子分裂所形成的胚包围其中;与此同时,合点室胚乳细胞的细胞核进行1次核分裂但不伴随胞质分裂,在合子期便形成具有两个细胞核的胚乳合点吸器;胚乳吸器为胚乳本体的发育从珠被与合点吸收并转送营养物质。胚胎发生属于柳叶菜型,经原胚期、心胚期、鱼雷胚、子叶胚形成成熟种子。珠被绒毡层发达。对胚乳本体以及球胚的流式细胞仪细胞核DNA分析表明,胚的DNA含量为二倍体,而胚乳为三倍体。

The experiment was conducted by means of routine paraffin-embedded sectioning technique to offer some information for embryology and taxonomy of Plantaginaceae.The results were as follows：Mature megagametophyte was of Polygonum-type with 7 cells and 7 nuclei.Fertilization resulted in zygote and primary endosperm nucleus.Development of endosperm was of Cellular-type,as the first division of primary endosperm nucleus separated a micropylar and chalazal chamber.The micropylar chamber turned into 2-or 4-celled by one or two vertical division at right angle to each other,then a transverse division in each cell formed 4 or 8 cells arranged in two tiers.Each cell of the micropylar tier（2 or 4 cells） developed into a one-nucleated micropylar haustorium,and the other 2 or 4 cells of the lower tier gave rise to a endosperm proper surrounding embryo.Meanwhile the chalazal chamber developed into a binucleate haustorium by mitosis without division of cytoplasm.Haustorium absorbed and transformed nutrition from integument and chalaza to endosperm proper.The embryogeny conformed to Onagrad type,and mature seed developed from proembryo-heart-torpedo-cotyledon stage.Integument tapetum was well-developed.Relative nuclear DNA content of nuclei was measured by flow cytometry which showed that embryo was diploid and endosperm was triploid.