Study On Numerical Taxonomy About15Species Of Rhododendrons In Southwest Sichuan

This study used the15species of Rhododendron in the southwest of Sichuan as the materials, and studied on numerical taxonomy of their phenotypic characters and pollen characters, in order to explore the genetic relationship among the species and seek new method for the classification of Rhododendron, and to provide the theory basis for the exact classification of wild Rhododendron. The major methods and results are as follows:1. The research of numerical taxonomy of the phenotypic characters:45phenotypic characters which including13dualistic characters,18multi-characters and14quantitative characters were selected and analyzed using SPSS18.0. Q cluster was using Squared Euclidean distance coefficient and R cluster was using Pearson correlation. They were using different cluster methods, the Q cluster was by Ward s method and the R cluster was by between-groups linkage.1) The result of Q cluster showed:through the squama having or not, the size of the flowers and leaves as standard, the15species of Rhododendron can be divided into2obvious characteristic sections. The first section had11species which belonged to Subgen. Hymenanthes. The second section had4species which belonged to Subgen. Rhododendron. The result of this cluster basically conformed to the traditional morphological classification.2) According to the squared Euclidean distance coefficient matrix among sections, we could get that in Sect. Hymenanthes about the squared Euclidean distance between R.lanatoides and the species of Subsect. Maculifera was minimum, and the genetic relationship between them was nearest; The squared Euclidean distance between the Subsect. Fortunea Sleumer and the Subsect. Maculifera was maximum, and the genetic relationship between them was farthest; In Sect. Rhododendron, the squared Euclidean distance between R.orthocladum and R.dendrocharis was maximum, so the genetic relationship between them was farthest.3) According to the result of R cluster, the characters were divided into different sections. The correlativity in the squama having or not, the size of flowers and leaves, the number of corolla lobe and the number of stamens etc. in sections was obvious. These characters are important to the classification in species.2. Use the electronic microscope to observe and contrast the pollen grains of the15species of Rhododendron, and study them by cluster analysis.1) The results of morphology showed that:All Rhododendron pollens had tetrad construction. Single pollen grains was spheroidal, globular or oblate with3aperture channels, and there were unequal haircuts among pollen grains. Some characters of pollen grains were similar, such as their shapes, the granular size and shapes on the extine, the shapes and quantity of cracks, the depth of break joints among tetrads, but there was heteromorphosis on the tetrad size and the ratio of germination aperture. The extine ornamentation and the ratio of germination aperture changed irregularly. And there were tetrads of some species that had changed, with irregular shapes.2) Select14pollen characters to do the cluster analysis, including4quantitative characters,1dualistic character and9multi-characters. According to the result of Q cluster, pollen characters of the same section did not get together, which revealed that pollen characters could not be used to be the basis for section’s classification, but they could be used as a supplementary mean to subsection’s classification when the section was clear by Q cluster analysis section. Rhododendron and section.Hymenanthes in separately.3) The correlation matrix of R clusters showed that the various characters was almost independent of each other, the correlation between them was not high.