大叶杨配囊及胚珠的形成和发育

本文应用细胞化学方法研究了大叶杨胚珠、胚囊的形成和发育过程中核酸、蛋白质及不溶性多糖的分布和消长。大孢子母细胞、大孢子四分体及功能大孢子中含较少不溶性多糖,但却含丰富的RNA和蛋白质。功能大孢子经分裂发育成八核的蓼型胚囊。四核胚囊开始积累细胞质多糖,成熟胚囊中除反足细胞外充满淀粉粒。反足细胞形成后不久即退化。助细胞具多糖性质的丝状器,受精前两个助细胞退化。卵细胞核对Feulgen反应呈负反应。二极核受精前由胚囊中部移向卵器,与卵器接触后融合形成次生核。发育早期的胚珠为厚珠心,双珠被。晚期,内珠被退化,故成熟胚珠为单珠被。四核胚囊时期,珠孔端珠心组织退化,胚囊伸向珠孔形成胚囊喙。合点端珠心组织含丰富的蛋白质和核酸,这一性质与绒毡层性质相似,可能涉及胚囊的营养运输。胚囊的营养来源于子房和胎座细胞内贮存的淀粉粒。

FORMATION AND DEVELOPMENT OF THE OVULE AND EMBRYO SAC IN POPULUS LASIOCARPA OLIVER

The formation and development of ovule and embryo sac in Populus lasiocarpa were investigated using cytochemical method for DNA, RNA, polysaccharides and proteins. The insoluble polysaccharides are at very low level in the MMC, tetrads and functional megaspore stages while RNA and protein are at higher level in all of them. The functional megaspore develops into a 8-uncleate embryo sac of polygonum type. The cytoplasmic polysaccharides are visible in 4-nucleate embryo sac. The mature embryo sac is filled up with starch grains except antipodal cells. The antipodal cells are ephemeral. The synergids have PAS positive filiform apparatus, and degenerate before fertilization. Feulgen reaction is negative in the egg nucleus but is positive in the nuclei of others in the embryo sac. The two polar nuclei move to the egg apparatus from the middle of the embryo sac before fertilization, and after contacting with the egg apparatus, they fuse with each other to form a secondary nucleus. In the early developmental stage, the ovule shows cras sinnucellate and bitegmic, Afterwards, the inner integument degenerates, so the mature ovule is unitegmic. The nuceleus at the micropylar end degenerates in 4-nucleat embryo sac stage. The embryo sac projects into the micropyle, forming a embryo sac beaker. The nuceleus at the chalazal end contains rich proteins and nucleic acids. This property is the same as that of the tapetum, and may be involved in the transfer of food materials to the embryo sac. The nutrition of embryo sac comes from starch grains which stored in the cells of ovary and placenta.