Study On Some Phylogenetic Problems In Impatiens L. Of China

The phylogeny of Impatiens L.is comprehensively investigated based on micromorphological features of seed surface,palynology,floral organogenesis and molecular systematics.The main results are summarized as follows.1.Micromorphological features of seed surface of 15 species in Impatiens L.have been examined under the scanning electron microscope (SEM).According to the characters of the epidermal ornamentation of seed coat and the granules on the cell surface,the micromorphological features of seed surfaces in Impatiens could be divided into four types, namely,laevigate,granulate,reticulate and protrusive.The latter two types could be further divided into subdivisions according to the shape of the epidermal ornamentation of the seed coat.The areolate subtype and the reticulate-colliculate subtype were observed for the fist time.The results showed that the micromorphological features of seed surfaces in Impatiens were different among different species,and therefore it could be used as reliable diagnostic characters to identify species.The micromorphological features of seed surface were closely correlated with the gross morphology characters,so it maybe suggests the phylogenetic relationships in Impatiens. 2.The pollen morphology of 36 species of Impatiens in China has been examined under SEM.In these species,the pollen grains are goniotreme,3-colpate or 4-colpate,actinomorphic or zygomorphic, reticulate exine ornamentation.The size of pollen grains is 18.7-45.1×12.5-25.7μm.The evolutionary trend of the germination apertures of the pollen grains in these species may be from the 3-colpate to 4-colpate germination aperture.The species of 3-colpate germination aperture such as I.omeiana etc may be an original group,while the species of 4-colpate germination aperture such as I.reptans etc may be an evolutive group.The length of polar axis,equarorial axis,width of apertures and spine,and the shape of pollen are different to some extent among these different species.The results showed that the species of Impatiens can be classified on the basis of the pollen morphology, especially the granule characters of exine ornamentation.The exine sculptures are different among different species and therefore can provide some proof for identification of some species in Impatiens.3.The floral organogenesis of four species in Impatiens,which represent different floral morphology,has been observed for the first time under SEM.The development pattern and processes of floral organogenesis of the four species were observed.The evolutionary trend of the sepals in these species may be from five sepal primordia initiate independently and develop completely to five sepal primordia initiate independently and only three develop,then to only three sepal primordia initiate independently and the other two primordia fuse postgenitally with the anterior petal primordia.The four lateral petal primordia grow independently,while the anterior petal primordium always grows first. Five stamen primordia are initiated on an inner whorl,alternating with the corolla.Five carpel primordia arise simultaneously.From the point of floral organogenesis,the species of five sepal primordia initiate independently such as I.arguta represent the original group in Impatiens, while the species of only three sepal primordia initiate independently such as I.armeniaca etc may be represent the evolutive group in the genus.4.The nrDNA ITS and cpDNA trnL-F of more than 30 species, which represent most of the morphological types,were sequenced.Based on these two sequences four phylogenetic trees are constructed using Hydrocera triflora,Tetramerista sp.and Souroubea loczyi as out groups. The results showed that Balsaminaceae is a monophyletic,and Hydrocera triflora placed the root of phylogenetic trees is sister to Impatiens. Species including oval or broad-spindly capsule formed a clade,and club or strip capsule formed another clade.The result implied the fruit shape maybe an important character to indentify species in Impatiens.By analysing the phylogenetic trees,both the shape of labellum and the length of calcar are important characters.However,the flower-subtending bract and the number of lateral sepal are less important.Based on analyses the phylogenetic trees,the following clade,namely,I. hunanensis and I.longicornuta clade have high bootstrap support,so the author suggest that they should be formed a species;however,I.siculifer and I.siculifer var.porphyrea are placed different clades,so the latter come out in a more significant position which is upgraded an independent species.5.The shape of the fruit,lower sepal(including the spur)and structure of the inflorescence are completed as the most important characters of taxonomy in Impatiens.Moreover,the taxonomic positions of some species such as I.longicornuta etc are discussed.A new species of Impatiens,I.rupestris K.M Liu et X.Z.Cai,sp.nova from China (Hunan Province,Jiangyong County)is described.