The Systematic Relationships Of Acorus Together With Araceae And Typhales

In the thesis, the systematic relationships of Acorus together with Araceae and Typhales are discussed on the basis of features from micromorphology, anatomy, pollen morphology and floral development, with the aid of the data from their embryology, cytology, chemotaxonomy and molecular biology. Firstly, it is found that there are many obvious differences between Acorus and Araceae. Their differences are based on many aspects which include characteristics of morphology, anatomy and epidermis of leaf, types of tapetum in anther walls , patterns of endothecial thickenings, and ways of development of endosperms, presence or absence of perisperm, components of photochemistry, and sequences of rbcL. The studies support the viewpoint that Acorus should be removed from Araceae to an independent family. Secondly, according to the stem and leaf anatomy, leaf epidermis, pollen morphology and floral development, it is found that there are no close relations between Acorus and Typhales, especially in the aspect of floral development. In the course of floral development of A. calamus, neither bracteloe primordium nor common primordium occurs in the whole course. Early development of the flower is strongly unidirectional. Three shield carpels develop into a pistil. In Sparganium fallax, each female flower has a bracteole. The bracteole primordium and the floral primordium originate from a complex structure. A single saccate carpel develops into a pistil. In staminate flowers, petal and stamen primordia initiate spirally. Evidence from all fields indicates that the relations between Acorus and Sparganium are distant. Thirdly, it is possible that Acorus is in an isolated, primitive position among the monocotyledon. The systematic position of Acorus among the angiosperms deserves to be studied deeply.