Leaf Morphological Differences Of Ulmus Macrocarpa (Ulmaceae)

Ulmus macrocarpa,belongs to Ulmus L(Ulmaceae),is one of the world's famous four street trees,mainly distributed in northeast China,north China,east China and central China.In order to reveal the phenotypic variation degree and variation regularity of the populations,several methods were used to analyze the 18 phenotypic traits of 22 populations in U.macrocarpa,including nest variance analysis,principal component analysis,correlation analysis and so on.The micromorphological characteristics of the leaves of U.macrocarpa were observed by scanning electron microscopy(SEM),and the adaptability of the micro-morphology and environment of the leaves were studied.The main results were as follows:(1)The changes of environmental factors in U.macrocarpa sampling sitesThe changes of environmental factors showed that organic matter is almost the same as available nitrogen,available potassium and water content.The changes of latitude and longitude,annual precipitation is similar as well.Principal component analysis of environmental factors indicated that available nitrogen,organic matter,longitude,and monthly mean temperature were dominant factors.(2)Leaf phenotypic diversityAll phenotypic traits of U.macrocarpa had significant correlations within populations and among populations.The mean coefficient of variation of phenotypic traits was 18.353% and the variation range was from 6.769% to 30.837%,and there existed abundant variation within populations and among populations.The mean relative difference among the 18 phenotypic traits was 45.13,and the variation range was from 23.79 to 60.34.For the relative difference among the 22 populations of U.Macrocarpa,the highest was in SDLC(67.49)and YQS(26.74)was the lowest.The mean phenotypic differentiation coefficient(Vst)of populations was 93.955%,the variation range was from 80% to 98.545%,and the variation among populations(49.290%)was higher than that within populations(3.229%),suggesting that the variation among populations was the main part of the phenotypic variation.Shannon-Wiener information diversity index was from 2.71315 to3.09000,and Simpson genetic diversity index was from-0.30111 to 0.05194.Shannon-Wiener information diversity index and Simpson genetic diversity index were2.28310 and 0.12215 respectively,which indicated that there was high genetic diversity among populations.The principal component analysis(PCA)showed that the first four principal component added up to 88.066%.The order of the PCA value tested for the traits was leaf>petiolet>vein.The correlation analysis between phenotypic traits and environmental factors showed that latitude had the greatest effect on traits,followed by longitude and monthly mean temperature.Effects of available nitrogen and organic matter on traits are also significant.The U.macrocarpa investigated could be divided into two groups according to the UPGMA cluster analysis.(3)Leaf epidermis micromorphological characteristicsThe cells of both upper and lower epidermis are covered by thick corticle with waxy and crystal.There are two types of epidermal hair,unicellular hairs and multicellular hairs.There were significant differences in epidermis densities among the populations and between the upper and lower epidermis.The stomata only distributed in lower epidermis and the stomatal morphology and stomatal density also exist differences among populations.The principal component analysis was conducted after quantification of leaf micro-morphological features.The results showed that the cumulative contribution rate of the first four principal components was added up to 89.252%.The contribution rate of epidermal hair is greater than that of stomatal.The correlation analysis between micromorphology of leaf and environmental factors showed that the stomatal characteristics are influenced by temperature,and the epidermis density is mainly affected by altitude.