The Karyotype And Seed Morphological Research Of Seven Species Of Sorbus

The genus Sorbus of the Rosaceae is in the center position which is relativelyprimitive of Maloideae, with high variability and a lot of polyploids hybrid origin.The classification and species definition are controversial. Seven species of Sorbuswere taken as the experimental materials in this paper. The conventional squashedmethod was adopted to analysis the somatic-cell-chromosomes. Besides, we alsoconducted anatomy observation to the seeds of five species of them. The aim ofthis paper was to provide evidence of cytology and seed anatomical, and toimprove the situation that our country as a center of the origin and evolution ofSorbus is lack of cytological evidence. The major conclusions are listed as follows:1. The method of chromosome production of SorbusAccording to existing plant cytological achievements, the study methods ofchromosome was improved and a set of simple, economical and efficient karyotypeanalysis method was explored. The apex part of germinant seeds was selected assamples and put in Colchicine(0.1%) and8-Hydroxyquinoline(0.002mol/L)mixture(1:1) for2hours. Then fixed in freshly prepared Carnoy’s fixed liquid (1:2acetic-alcohol) for24h, hydrolyzed in the mixed solution HCl(1mol/L) in constanttemperature bath(60℃) for10minutes, and stained with improved fuchsin solution.Squashing, microscopic examination and measurement were then carried on. Thepairing and arrangements of chromosomes were made using Adobe photoshop andAuto CAD.2. Karyotype analysis of SorbusThe results showed that all the chromosomes of hazelnut germplasms werediploid and the number is34; The actural length of chromosomes belonging to smallchromosomes. The karyotype formula of S. alnifolia, S. dunnii, S. folgneri, S.amabilis, S. pohuashanensis, S. setschwanensis and S. koehneana was2n=2x=34=24m+2m(sat)+8sm,2n=2x=34=22m+2m(sat)+10sm,2n=2x=34=20m+2m(sat)+12sm,2n=2x=34=22m+10sm+2sm(sat),2n=2x=34=22m+2m(sat)+10sm,2n=2x=34=18m+2m(sat)+14sm,2n=2x=34=28m+2m(sat)+4sm. The variation ofasymmetric coefficient ranged57.5%-61.97%. According to Stebbins’ category, S.alnifolia belongs to “Type1A”; S. koehneana belongs to “Type1B”; S. dunnii and S.setschwanensis belong to “Type2A”; S. folgner, S. amabilis and S. pohuashanensisbelong to “Type2B”.3. Characteristics of seeds of SorbusThe shape of seeds are obovate or oval with different sizes. The color of seedcoat varies from brown to black. The seeds of the compound leaf group are smallerthan the simple leaf group in size and smooth without necessaries, and that the seed coat of the simple leaf group is coarse.In terms of anatomy, seed coat consists of inner epidermis, outer epidermisand a layer of transparent pectin in the middle. Out epidermis has a structure ofxylem fiber. Inner epidermis consists of3-5layers of living cells. In most cases,inner epidermis is thicker than outer epidermis. The outer epidermis of thecompound leaf group is thinner than the simple leaf group.Epidermal submicroscopic structure shows regular reticulum which formed bypentagon or hexagon units. In addition, there are clear distinctions between theseeds of the simple leaf group and the compound leaf group: the epidermalornamentation of the compound leaf group is thin-walled reticulum structure whilethe epidermal ornamentation of the simple leaf group is thick-walled reticulumstructure.