草地早熟禾胚发育类型及无融合生殖特征

【目的】通过对草地早熟禾不同时期胚囊发育过程的观察，掌握其胚囊类型和无融合生殖胚囊发育特征，为更深入了解无融合生殖的机理、选育中国本土草地早熟禾新品种提供理论基础。【方法】采用改良的石蜡切片技术，即FAA固定材料，多梯度二甲苯透明，切片厚度8 µm，苏木精（30 min）伊红（5 min）双重染色，观察并分析草地早熟禾的胚囊发育类型和特征。【结果】在石蜡切片中，观察到草地早熟禾巴润生殖过程中的5种胚囊类型，有性生殖胚囊所占比例为21.44%、体细胞无孢子生殖胚囊为49.67%、孤雌生殖胚囊为10.72%、助细胞胚胎和反足细胞胚囊分别为4.82%和7.66%，其中，体细胞无孢子生殖胚囊为主控型胚囊；草地早熟禾有性生殖胚囊为典型的蓼型胚囊；草地早熟禾同一胚珠中存在有性生殖胚囊、体细胞无孢子生殖胚囊或无配子生殖胚囊共存于一体的多胚现象，多胚出现频率为5.69%，其中，卵细胞形成的有性生殖胚囊与助细胞形成的胚囊极性相同，反足细胞形成的胚囊与卵细胞有性生殖胚囊极性相反；无孢子胚囊发育极不规则，通常单个发生或2个以上发生而形成多胚，2个胚囊并存现象居多。【结论】草地早熟禾生殖方式多样，具备有性生殖和无融合生殖2种生殖方式，为兼性无融合生殖植物，其无融合生殖方式以体细胞无孢子生殖为主，此外还有少量孤雌生殖和极少量的无配子生殖。

Embryo Types and Characteristics of Apomixis in Poa pratensis L.

【Objective】The embryonic development process in different periods was observed to understand the embryonic types and features of apomixis, which can provide a theoretical basis for further understanding the mechanism of apomixis and selecting local new varieties of Poa pratensis L..【Method】 The improved paraffin section technique was used to identify the types and characteristics of embryo in P. pratensis L., in which the material was fixed in FAA and cleared in multisegment dimethybrnzene separately, and the slice thickness was 8 µm. Ehrlich’s hematoxylin (30 min)-eosin (5 min) double stain was involved in the process.【Result】 Five embryonic types were observed during reproductive development process in P. pratensis L., and in which there were sexual reproduction embryo (21.44%) , somatic apospory embryo (49.67%), parthenogenesis embryo (10.72%), synergids embryo (4.82%) and antipodal cell embryo (7.66%), respectively. The somatic apospory embryo was dominant embryo presence of them. Sexual embryo sac was typical Polyonum type embryo sac. There were sexual embryo sac, apospory embryo sac or diplospory embryo sac coexisting in one ovule to form polyembryony in P. pratensis L., and the occurrence frequency of polyembryony was 5.69%. The polarity of the sexual embryo sac was the same with synergids embryo sac，and it was opposite to antipodal cell embryo sac then. Somatic apospory embryo sac varied irregularly during its development, with the presence of single or more than two sacs to develop polyembryony. It was shown that the presented two embryo sacs were the majority. 【Conclusion】 There are various reproduction patterns in P. pratensis L., with sexual reproduction and apomixes. It is a facultative apomixis plant, in which, the somatic apospory is dominant mode of reproduction in apomixes, in addition, a small amount of parthenogenesis and apogamety are present among them.