中国鹅掌楸与北美鹅掌楸种间杂交的胚胎学研究*
The Embryological Studies of Interspecific Hybrids between Liriodendron tulipifera L, and L. chinense(Hesml.)Sarg.
-
摘要: 应用控制授粉、常规石蜡切片技术研究了中国鹅掌楸与北美鹅掌楸种间杂交后的胚胎发育过程。结果表明:(1)控制授粉后花粉正常萌发,并有较多的花粉管进入柱头,但花粉管在花柱内生长缓慢甚至解体;(2)花粉萌发6d后花粉管经花柱沟、珠孔塞和珠心冠原组织进入胚囊进行珠孔受精,20d时游离核胚乳细胞化,发育形成2~4个细胞厚的狭长组织,35d后可观察到球形胚;(3)随着胚和胚乳的发育,珠被发育形成种皮。授粉时,胚珠具2层珠被,外、内珠被均由外表皮、中层和内表皮组成;胚与胚乳发育期间,珠被各层发生了一系列的变化,最终种皮由外珠被的外表皮细胞形成的膜层和中层细胞形成的气室以及内、外珠被内表皮细胞形成的硬化层组成;(4)受精时成熟胚囊及到达珠孔的花粉管的数目较少,受精频率较低;(5)受精过程基本正常,但胚和胚乳发育不协调,导致胚在发育早期败育,很难观察到后期胚的发生。Abstract: The embryogenesis of interspecific hybrids between Liriodendron tulipifera and L. chinense was studied by means of artificial pollination and routine paraffin-embedded sectioning technique. The results were:(1)The pollen of L. tulipifera germinated normally after artificial pollination,and more pollen tubes could grow into stigma but a lot of pollen tubes grew slowly and even broke up in the style canal;(2)When the pollen has germinated for six days,the pollen tube reached the embryo sac finally through the style canal,obturator and nucellar cap,then,the porogamy was conducted.After 20 days, the cellular endosperm was formed first as a narrow tissue of 2 to 4 eclls in thickness. The spherical embryo could be observed after 35 days;(3)The seed coat was formed by integment following the development of embryo and endosperm. The antropous has two layers integments. Both of them were formed exopleura, middle layer and endopleura. Each layer of integment experienced a series of changs when the embryo and endosperm developed. At last,the seed Coat was consisted of the membrane layer formed by exopleura of exointegment, air chamer formed by middle layer and hardening layers formed by the endopleura cell of inter integument and outer integument;(4)The number of mature embryo sacs and pollen tubes reaching micropyle was too less to fertilize;(5)The course of fertilization was normal on the whole,but the development of embryo and endosperm was not in harmony, which resulted in the early abortion of embryo,so it was difficult to observe the later development of embryo.