Fruits And Seeds Morphological In Sorbus Section Sorbus Of China

The genus Sorbus of the Rosaceae contains sect.Sorbus,sect.Aria and sect.Micromeles,in which the sect.Sorbus contains all the pinnately compound leaf species,while the single leaf group is placed in the sect.Aria and sect.Micromeles.Fruits and seeds characters of 31 species and 7 varities were obeserved,and taxonomic value traits and phylogenetic relationship were analyzed in this research.Accordingly,the morphological characteristics could be an identification key to species of the Sorbus is established.The main conclusions are indicated as follows.1.The characteristics of infructescencesIndumentum and length of infructescences as well as the number of fruits per infructescence were significantly different among the taxon,which could provide the basis for identification and classification.Infructescences smooth,sparsely brown-villus or densely brown-villus;Infructescences length ranged from 1.67 cm to 9.91 cm,the shortest was Sorbus reducta var.pubescens L.T.Lu,the longest was Sorbus harrowiana(I.B.Balfour & W.W.Smith)Rehder?The number of fruits has also difference among the taxon.There were only 6 grains of S.reducta var.pubescens and Sorbus filipes Handel–Mazzetti,while there were 153 grains of S.harrowiana.2.The characteristics of fruitsFruit shape of Sect.Sorbus was similar,mostly globular or subglobular.Among different taxon,fruit color of different maturity of the same classification group varies greatly,there are white,light pink,cyan yellow,red,purplish red,cyan pink,orange,etc.,and often appear dark pink to light pink to white,cyan to white and other gradual colors.There were also significant differences in fruit size among different taxon,the smallest Sorbus kiukiangensis Yu was only 0.42×0.48 cm,while the largest Sorbus ursina was 1.02×1.18 cm..Persistent flower was discovered in fruit apex of Sect.Sorbus.Length and indumentum of calyx,style,filaments and ovary are different among taxon,which can be used for the identification and classification of species.The observation of the persistent flower showed that the calyx size was 1.04×1.30 mm to 3.15×2.16 mm,the smallest is S.reducta var.pubescens,the largest is Sorbus filipes.There were three kinds of indumentum in the calyx of different taxa,both inner and outer of calyx were smooth,the inner of calyx was fluffed and both inner and outer of calyx were fluffed.Style length was 1.33 mm to 4.66 mm,the shortest is Sorbus hupehensis C.K.Schneider,the longest is Sorbus filipes.Styles united or separated,smooth or hairy.Filament length was 0.93 mm to 3.89 mm,the shortest is Sorbus laxiflora Koehne,the longest is Sorbus filipes.Filaments smooth,sparsely brown villus or densely brown villus.The indumentum of the ovary upper apex was smooth,1/2 sparse brown villus,1/2 dense brown villus or overall brown villus.Fruit apex of the Sect.Sorbus has persistent flower,so that characteristics of the flower can still be known during the fruit period,which was beneficial to the accurate identification of the species.Observation of the flowers,the flowers and the flowers showed that the other characters except the color has less difference from the flowering stage.Calyx is between 1.22×1.08 mm to 3.15×2.16 mm,with Sorbus muliensis McAllister,the largest is Sorbus filipes.There were three kinds of indumentum in the calyx of different taxa,both inner and outer of calyx were smooth,the inner of calyx was fluffed and both inner and outer of calyx were fluffed.Styles united or separated,smooth or hairy.Style length was 1.33 mm to 4.66 mm,the shortest is Sorbus hupehensis C.K.Schneider,the longest is Sorbus filipes.The filaments were smooth,sparsely brown villus or densely brown villus.The range of length variation was 0.93 mm to 3.89 mm,and the shortest is Sorbus laxiflora Koehne,the longest is Sorbus filipes.The indumentum of the ovary upper apex was smooth,1/2 sparse brown villus,1/2 dense brown villus or overall brown villus.3.The characteristics of seedsThere are some differences in color and shape,size,thousand–grain weight and micromorphology of seed coat among different taxon of Sect.Sorbus,which can provide the basis for species identification and classification.Seed color of Sect.Sorbus was mainly reddish brown,a few of them were yellow,yellowish brown and black brown.Most of seeds were obovate,a few of them were narrow obovate and wide obovate.Seed size of different taxon ranged from 2.71×1.37×0.65 mm to 4.17×2.28×1.18 mm,the smallest is S.sargentiana,the largest is S.filipes.The ratio of length to width varied from 1.50 to 2.17.The distance from the umbilicus to the widest of the seed was from 0.71 mm to 1.91 mm.The variation range of thousand–grain weight is 0.53 gram to 5.25 gram.Micromorphological characteristics of the tasta of Sect.Sorbus were different among species,and could be divided into two types: reticulate and ridge–reticulate.The reticulate could be divided into four subtypes: regular shallow reticulate,regular polygon reticulate,regular oval reticulate and irregular shallow reticulation.The ridge–reticulate could be divided into two subtypes: ridge–reticulate and ridge–shallow reticulate.4.Taxonomic importance of fruits and seeds morphologyThe results of principal component analysis and cluster analysis showed that the micromorphology of testa,the length of infructescences,the indumentum of ovary,the combination of style,the length of style,the indumentum of infructescences were important morphologies in the identification of species in Sect.Sorbus.However,these morphological characteristics doesn't make much sense for present classification of subgroup.In conclusion,the study of fruit and seed morphology has evident reference value for the identification and classification of Sect.Sorbus.Based on the results of infructescences,fruits,seeds morphology studies and the type specimen,it is suggested that S.unguiculata,S.laxiflora and S.hypoglauca should be treated as independent species.