大车前胚乳发育的超微结构研究

采用透射电镜技术对大车前(Plantago major L.)胚乳发育的超微结构进行了研究。结果表明:(1)大车前为细胞型胚乳;初生胚乳核经一次横分裂产生1个珠孔室细胞和1个合点室细胞;珠孔室两次纵向分裂一次横向分裂形成2层8个细胞,位于上层的4个细胞发育为4个珠孔吸器,位于下层的4个细胞发育为胚乳本体;合点室细胞进行一次核分裂,发育为两核的合点吸器。(2)珠孔吸器呈管状插入珠被组织,珠孔端细胞壁加厚呈现少量分支并具有壁内突,壁内突周围细胞质里分布着大量线粒体、粗面内质网、高尔基体、质体等,细胞核与核仁明显,细胞质浓厚,代谢活动旺盛;球胚期,珠孔吸器的体积呈现最大值,珠孔吸器周围的珠被组织均被水解,形成明显的空腔。珠孔吸器从珠被组织吸收并转运营养物质至胚乳本体,参与胚乳的构建与营养物质的贮藏。球胚后期,珠孔吸器逐渐退化。(3)4个胚乳本体原始细胞具旺盛的分生能力,经不断的平周与垂周分裂增加胚乳细胞数目,使胚乳本体呈现圆球体状,并将胚包围其中;珠孔吸器、合点吸器以及珠被绒毡层吸收转运的营养物质贮存在胚乳本体;球胚后期,随着胚柄的退化,胚体周围的胚乳细胞被水解,为发育的胚所利用。(4)合点吸器的2个细胞核与核仁巨大,线粒体、质体、高尔基体、内质网主要绕核分布,液泡化明显;胚体与胚乳本体的体积增大,逐渐将合点吸器向胚珠合点部位挤压,合点吸器周围的合点组织逐渐被水解,形成巨大空腔。合点吸器自珠心组织吸收并转运营养物质至胚乳本体,参与胚乳的结构构建与营养物质的贮藏。球胚后期,合点吸器逐渐失去功能,呈现退化状态。

Ultrastructural Studies on Development of Endosperm in Plantago major L.

Ultrastructural features during endosperm development of Plantago major L.were viewed and described by means of transmission electron microscope(TEM).The results are as follows:(1)Cellular type endosperm.The primary endosperm nucleus divides into a micropylar and chalazal chamber.The micropylar chamber becomes 8-celled in two tiers by two vertical and a transverse divisions.The four cells in the micropylar tier develop into four micropylar haustoria.The lower four cells develop into endosperm propers.The chalazal chamber develops into a binucleate haustorium by mitosis without division of cytoplasm.(2)The tubular micropylar haustorium penetrates into integument and its micropylar wall has a large amount of ingrowths and a few branches.There are a lot of mitochondria,rough endoplasmic reticulum,golgi bodies and plastids etc.around the ingrowths.The nucleus and nucleolus are obvious and the cytoplasm is dense.The metabolism is exuberant.During the period of global embryo,the micropylar haustorium shows the maximum size and integument around micropylar haustorium is hydrolyzed and resulted in a cavity.Micropylar haustorium absorbs and transforms nutrition from integument to endosperm proper to engage in forming endosperm proper and storing nutrition.At the later stage of global embryo,the micropylar haustorium degenerates gradually.(3)The four original cells of endosperm proper have vigorous meristematic ability,and divide anticlinally and periclinally.The endosperm proper surrounding the embryo is spherical-shaped.The nutrition absorbed by the haustorium and integument tapetum is stored in the endosperm proper.With degeneration of the suspensor,the endosperm proper is hydrolyzed in the period of later global embryo.(3)The two nuclei and nucleoli of chalazal haustorium are large.Mitochondria,plastids,golgi bodies and rough endoplasmic reticulum are located around the nucleus.Chalazal haustorium becomes high vacuolated.Along with the embryo and endosperm proper increasing in size,chalazal haustorium expends towards the chalazal end of the ovule while the chalaza surrounding the chalazal haustorium is hydrolyzed gradually,resulting in a cavity.Chalazal haustorium absorbs and transforms nutrition to the endosperm proper to engage in forming endosperm proper and storing nutrition.During the later period of global embryo,the chalazal haustorium loses its function and degenerates gradually.