| Plants of Malus Mill.are deciduous trees or shrubs of Rosaceae.M.hupehensis Rehd.is one of the species with the most variation and the most difficult classification in this genus,and the type specimen was collected from Hubei Province.M.hupehensis is a typical allotriploid,with many geographical types with complex variation,and it is also very difficult to distinguish it from related species.Therefore,it is of great significance to explore the taxonomic status of M.hupehensis and among the related species for solving the taxonomic problems of the Malus.Based on the classic plant taxonomy,in this study,several geographical types of M.hupehensis were then studied on the development of the ovary embryo sac to investigate the origin and intraspecific or interspecific relationship of M.hupehensis.In addition,the relationship and evolution of M.hupehensis and its related species were studied by the characteristics of leaf veins and the analysis of fruit carpels.1.The embryo sac development process of total of 8 taxonomic groups of 3geographical types and related species of M.hupehensis were observed and studied by paraffin preparation method.Among them,the research on the embryo sac development process of M.hupehensis var.taiensis,M.hupehensis(Tianmushan),M.micromalus,M.‘Dolgo’,M.‘Royalty’ and M.purpurea were reported for the first time.It provides theoretical guidance for the development and utilization of breeding and garden applications.The embryo sac growth process of M.hupehensis var.mengshanensis,M.hupehensis var.taiensis and M.hupehensis(Tianmushan)are similar,which is in line with the developmental mechanism of apomixis in M.hupehensis.The embryo sac development patterns of the studied related diploid species are in line with the general Polygonum embryo sac type,and the embryo sac development patterns of M.hupehensis apomixis and related species are quite different.The research results can suggest the hybrid origin of the allopolyploid of M.hupehensis,and also provide a certain basis for the classification between it and its related species.2.Refer to Yu Chenghong’s method of leaf vein research,the leaf venation sequences of the 31 geographic types are all reticulate veins,first-order veins straight,etc.,which have certain similarities,but there are certain differences in higher-order venation sequences.According to the characteristics of leaf veins,M.melliana is the most primitive group,and the lateral veins are parallel or straight,reaching the leaf edge.M.sieboldii,M.kansuensis,M.toringoides,M.xiaojinensis,M.prattii,M.ombrophila are relatively primitive groups.The leaf veins are mostly palm-shaped,the lateral veins are curved,and the ends are curved and knotted.The leaf veins of M.hupehensis,M.baccata,M.rockii,and M.sikkimensis are relatively similar in complexity.The leaf veins are reticulated,the lateral veins are curved,and the ends are not knotted,and the evolutionary status is higher.Among them,M.hupehensis and M.baccata have the highest degree of evolution.Based on the characteristics of venation sequence,a classification key table of 31 geographical types was compiled.According to the analysis of the coefficient of variation,cluster analysis and principal component analysis of the studied groups,the same trait has different degrees of variation within different species,and the variation of leaf vein logarithms within the species is relatively stable,and the screened traits can be used as the research group.It is the main basis for intraspecific or interspecific division and has certain classification significance.3.The anatomical observation and analysis of the fruits of 12 taxa of M.hupehensis and related species,the number of fruit carpels of Riwa crabapple is reported for the first time,and the number of carpels of other crabapples is verified.The number of carpels in most crabapples was roughly consistent with previous reports,but different in M.hupehensis var.mengshanensis.Traditionally M.hupehensis var.mengshanensis differed from M.baccata mainly by the fruits with 3 or 4 carpels,and the characteristics of calyx.But in this study,it was found that there are 3 to 5 carpels in M.hupehensis var.mengshanensis,and 50% of them are 5 carpels.Thus,the distinction between M.hupehensis and M.baccata were greatly weaken.Based on the characteristics of leaf venation and the number of fruit carpels,it is referred that it might be a good idea to combined M.hupehensis into M.baccata as a subspecies,and it might be good to solve the taxonomic problems between the two species. |
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