The Research On Classification Of Acer Stenolobum And Its Relatives

Acer stenolobum,A.stenolobum var.megalophyllum and A.pilosum are belonging to the genus of Acer of the family Aceraceae.Analysis of classical taxonomy,scholars at different stages believe that there is controvery of the taxonomic status of A.stenolobum and A.stenolobum var.megalophyllum.In this study,morphological and comparative anatomical methods were used to analyze and compare the phenotypic traits and secondary xylem tectonics differences between the A.stenolobum,A.stenolobum var.megalophyllum and A.pilosum,and their classification and integration were discussed.The main research results are as follows:(1)By using of relative extreme value and coefficient of variation to analysis the A.stenolobumand the A.stenolobum var.megalophyllum at different point of periods.The results showed that the phenotypic traits of the fruit is more stable than the leaves.As an index of classification of the leaf size and double-wing connection angle for A.stenolobum,A.stenolobum var.megalophyllum and A.pilosum,and the average coefficient of variation was relatively large,they do not support the “Flora of China” and other local flora to discussion the Taxonomy status of them.By comparing the relative extreme values and variation coefficients of phenotypic traits of A.stenolobum,A.stenolobum var.megalophyllum and A.pilosum from the same area,shows that the stability of phenotypic traits selected from the three plants ranged from large to small order is : A.pilosum,A.stenolobum,and A.stenolobum var.megalophyllum.(2)The epidermis and the lower epidermis of the leaves of A.pilosum have surface fur,and do not fall off during the life cycle.It is slightly different from the records of “Flora of China” to the A.pilosum.The leaf epidermal cells of the three are polygonal or irregular,and the vertical circumferential walls are straight or arched,only the lower epidermis distributes the stomata,and the protection cells are kidney shaped,and the stomata are long oval.There are no significant differences in stomatal density,stomatal index and stomatal width among the three species.According to the relationship between the phylographic evolution of plant leaf veins proposed by Xu Bingqiang,the characteristics of the vein order of A.stenolobum,and A.stenolobum var.megalophyllum are basically the same,but the A.pilosum is more primitive than the A.stenolobum,and A.stenolobum var.megalophyllum.There are three types of tails with tails at one end,tails at one end,and tailless at both ends.According to the wood characteristics summarized by IAWA,the three types of wood ray width,conduit length,conduit width,and wood fiber length are all of the same type.(3)There was little difference in secondary xylem of stems of A.stenolobum,A.stenolobum var.megalophyllum and A.pilosum.All three of them are ring-shaped porous materials,and the early wood is mainly composed of single holes,while the late wood is mainly composed of multi-holes or tube holes.Axial parenchyma cells are arranged neatly,and the wood rays are mostly single-row ray,and prismatic crystals are abundant.The type of perforated plate is mostly single perforated plate,and the ladder shaped perforated plate is found in the threaded catheter.There are 5 kinds of striate types,which are porous catheter,reticulated catheter,threaded catheter,porous + threaded catheter and corrugated + ladder catheter.There are 3 tail types which are both ends with taile,one end with taile and both ends without taile.According to the wood characteristics summarized by IAWA,the width of the wood ray,the length of the catheter,the width of the catheter and the length of the wood fiber belong to the same type.Compared the differences between the roots(radicle)and the stem(young stem)catheter of A.stenolobum,A.stenolobum var.megalophyllum and A.pilosum,the results showed that the characteristics of the vessels are small and similar.In conclusion,A.stenolobum and A.stenolobum var.Megalophyllum have little difference in phenotypic characters and the secondary xylem structure,which supports the mergedprocess of “Flora of China”.The leaves of A.pilosum had fur,and the cleft A.stenolobum only had hair in the veins,and the veins of A.pilosum were more primitive than those of A.stenolobum.Other phenotypic traits and secondary xylem structures were similar to that of A.stenolobum.Our research provided evidence for treat A.stenolobum as a variety of the A.pilosum in“Flora of China”.