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.