小叶丁香引种栽培条件下种子败育的解剖学研究

为探讨小叶丁香在北京栽培条件下种子败育的问题,对其胚胎发育过程进行了解剖学观察研究。结果显示:(1)小叶丁香人工异花授粉坐果率为20.37%,天然授粉坐果率为9.13%,人工自花授粉以及去雄套袋授粉均未坐果;各种授粉方式结实率均为0。(2)小叶丁香花药壁发育为基本型,腺质绒毡层,胞质分裂为同时型,小孢子四分体排列方式以四面体型为主,2-胞成熟花粉;倒生胚珠,单珠被,薄珠心,直线型大孢子四分体,胚囊发育为蓼型,核型胚乳,胚发育为紫菀型,先后形成球形胚、心形胚、鱼雷形胚和子叶胚;9月1日以后,子叶胚发育停滞,细胞逐渐降解。研究表明,栽培条件下,小叶丁香为异花授粉植物,人工异花授粉可提高植株坐果率,但未获得种子;其大小孢子及雌雄配子体发育、传粉受精过程、胚胎发育初期均正常,但后期发育停止,是小叶丁香引种栽培条件下种子败育的关键环节。

Anatomical Study on Seed Abortion of Syringa microphylla in Cultivated Condition

To better understand the aborted seed of cultivated Syringa microphylla Diels in Beijing,we observed the embryo development of S.microphylla.(1)The fruit setting rates from artificial self-pollination and controlled emasculation were 0 while intraspecific crossing pollination and natural pollination were 20.37% and 9.13% respectively.The setting rates from four pollination methods were all 0;(2)The anther wall conformed to the basic type and glandular tapetum.The cytokinesis of the microspore mother cells in meiosis was the simultaneous type,and microspore tetrad was mainly tetrahedral shape.The mature pollen grains were of 2-celled type.The ovule was anatropous,unitegmic and tenuinucellate,megaspore tetrad was linear shape.The development of the embryo sac was the polygonum type.The endosperm developed to be the nuclear type and the embryo the asterad type.The globular embryo,heart-shaped embryo,torpedo embryo and cotyledonal embryo were formed sequentially.However,the development of the cotyledonal embryo stopped and all cells gradually degraded in early September.The study showed that S.microphylla was cross-pollinated plant,the method of the intraspecific crossing pollination could increase the fruit setting rates,while no viable seed was harvested.The microspore and megaspore,male and female gametophytes,pollination fertilization and early embryo development were normal,but the later embryo growth stopped.