Mosses' Stem Structure And Application Of Stem Structure On Brachythecium Taxonomy

Bryophytes are small, herbaceous plants that grow closely packed together in mats or cushions on rocks, soil, or as epiphytes on the trunks and leaves of forest trees. They usually have only filamentous rhizoids, but no lignin, no real roots, and the sporophyte is parasitic on the gametophyte. So they are considered as the original high land plants. However studies of flora and systematic taxonomy have attracted lots of bryologists, currently the attempts to study stem structure, relationship between structure and environments, especially application of stem structure on taxonomy are less.14 mosses representing different habitats were chose in this thesis to study the relationship between stem structure and environments and discuss significance on taxonomy. Meanwhile, 3 mosses' stems were observed by transmission electron micrograph (TEM). By applying stem transverse sections on 32 species of Brachythecium reported in China, We look forward to supplying some evidence for Brachythecium systematic taxonomy. Conclusions are as follows:1. By having studied both Climacium japonicum erect and accumbent stems and also stems in different areas, we found epidermis, cortex and mainaxis comprised transverse section of stem. And thus stems' structures are the same, which shows as steady structure, stem could be one of criterions of taxonomy.2. Through treatment of strong acid and paraffin slicing, 14 mosses living in different habitats were studied and related data were also recorded.â‘  Stem transverse sections of mosses living in different environments have distinct characteristics. Stem of xeric mosses present thick cell walls in their epidermis and cortex and no mainaxis; However, stem of hydric mosses have mainaxis composed of small and thin wall cell or none; the stems contained a large number of parenchyma cells, Another 5 mosses' characteristics are in the middle of above, and mainaxis usually with more than 10 cells existed, and outer cortex width is larger than that of inner part.â‘¡ Xeric mosses' cells with thick wall have more end tails and pit fields, whose numbers are 1.572, 2.024; However, hydric mosses' cells with thin wall have less of both, and numbers are 0.990, 0.850; Another 5 mosses' relevant numbers are 1.355, 1.762.â‘¢ On TEM observation of Brachythecium salebrosum and Climacium japonicum...