| Lagerstroemia L.belongs to Lythaceae.The plants of Lagerstroemia are mostly deciduous or evergreen shrubs or trees,which are distributed in tropical and subtropical areas in the east,southeast and south of Asia.Lagerstroemia is an important economic ornamental tree species,and can also be used as furniture wood,building,etc.In this study,ribosomal,chloroplast and mitochondrial gene fragments were used to analyze the phylogenetic relationship of 13 species of Lagerstroemia,and the leaves of 16 species of Lagerstroemia were dissected,and their anatomical structure characteristics and interrelationships were analyzed.At the same time,their leaf venation was analyzed by cluster analysis.The results are as follows:(1)The leaf morphological characteristics of 16 species of Lagerstroemia were compared,and the results showed that there were differences.The leaf shape could be divided into elliptic,lanceolate and oval;The leaf base can be divided into wedge-shaped,peltate and tapering;The leaf tip can be divided into acuminate,cusp and obtuse;The leaf margin can be divided into full margin and shallow wavy;The leaf epidermis of most species is pilose along the main vein.The variation range of leaf area of 16 plants is 475.97～10434.2 mm2,the variation range of leaf circumference is 108.87～471.93 mm,the variation range of leaf length is 5 1～2 14 mm,the variation range of leaf width is 17.13～78.60 mm,and the variation range of leaf length to width ratio is 1.46～3.59.The leaf area,leaf circumference,leaf length and leaf width of L.speciosa are larger than those of the other 15 species.ANOVA univariate analysis of variance showed that the differences in leaf area,leaf circumference,leaf length and leaf width of 16 species of Lagerstroemia reached a very significant level.It can be considered that the morphological and quantitative characteristics of leaves have a significant impact on different species.Pearson correlation analysis showed that there was a good correlation between the five leaf morphological characteristics and quantitative traits.The results of cluster analysis were consistent with those of leaf traits.(2)The characteristics of leaf venation of 16 species of Lagerstroemia were described by species,and the number and characteristic data of leaf veins of 16 species were compared.The results showed that the characteristics of leaf veins of 16 species of Lagerstroemia were not significantly different except for the number of leaf veins.The characteristics of leaf venation of the same plant were consistent,showing a high degree of stability.Through ANOVA univariate analysis of variance,it was found that the number of secondary veins,the number of tertiary veins,the distance between secondary veins,the width of secondary veins,the length of secondary veins,and the included angle of secondary veins were significantly different.Therefore,it can be considered that the morphological and quantitative characteristics of leaves have a significant impact on different species.Pearson correlation analysis of leaf venation characteristics showed that there was no significant difference between 6 quantitative traits in 16 species,indicating that quantitative traits were relatively independent and less interdependent.(3)The leaves of 16 species of Lagerstroemia were dissected,and it was found that the internal structure of the leaves was the same,but the structure size of each part of different species was different.The epidermis is composed of flat cells.The cells are arranged neatly and tightly.The mechanical tissue is closely under the epidermis,with obvious distinction between palisade tissue and sponge tissue.There are differences in the size of different types of collenchyma,parenchyma,xylem,phloem,spongy tissue and palisade tissue.ANOVA univariate analysis of variance showed that the differences of anatomical characters reached a very significant level.It can be considered that the anatomical structure of leaves had a significant impact on the differences of different species.Pearson correlation analysis showed that most anatomical characters of leaves were correlated or highly significantly correlated.The results of cluster analysis are consistent with those of leaf morphological characteristics and leaf venation.The anatomical data of leaf venation can be used as a reference for classification of this genus.(4)A phylogenetic tree was constructed based on five gene fragments including ribosomal gene fragment ITS,chloroplast gene fragment matK,rbcL,psbA-trnH and mitochondrial gene fragment matR,and the characteristics of the joint sequence were analyzed.The phylogenetic tree was constructed using maximum likelihood method(ML),Bayesian method(B1),maximum reduction method(MP),and adjacency method(NJ).The results showed that the phylogenetic classification based on ML tree,BI tree and MP tree was consistent,and the support rate was high;NJ trees are slightly different,with low support rate.The 13 species of Lagerstroemia obtained are divided into two branches,one of which is L.anhuiensis,L.fordii,L.limii,L.sp.3,L.tomentosa,L.superpareticulata;L.candata,L.substata,L.glabra,L.guiliensis,L.indica,L.sp.1.L.sp.2 are one branch.(5)Comparing the morphological classification and molecular classification in this study,the classification results based on molecular means are more accurate than the morphological classification results.Although the morphological classification and molecular classification results are not completely consistent,both have reference value for the taxonomy of Lagerstroemia.Moreover,the results of both morphological and molecular classification systems can be used as evidence for 2-3 uncertain species being suspected new species,but the relatively high support rate of phylogenetic trees at the molecular level can more support the possibility of their being suspected new species.It is preliminarily concluded that molecular methods are more reliable for the classification and identification of new species within the genus Lagerstroemia.Compared with the ML tree based on the combination of chloroplast gene fragments matK,rbcL,psbA-trnH,the results showed that the support rate was generally low,and the identification ability of the combined fragments of nuclear gene,chloroplast gene and mitochondrial gene in the classification of Lagerstroemia speciosa was more suitable than the chloroplast DNA barcode,which provided molecular support for the interspecific definition,targeted breeding and phylogenetic research of Lagerstroemia speciosa.This study is based on four aspects of leaf morphological characteristics,leaf vein sequence,leaf anatomical characteristics,and phylogenetic analysis to carry out interspecific comparison and intrageneric classification of Lagerstroemia.The difference analysis shows that leaf morphological characteristics,leaf vein sequence,and leaf anatomical characteristics can be used as the main characteristics for identification and classification of Lagerstroemia,while the DNA bar code at the molecular level fills the gap of morphological classification from another aspect.This study has certain reference value for the identification and classification of Lagerstroemia. |
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