Diversification And Evolution Of Tracheary Elements In The Early Lineages Of Angiosperms

In this paper, a broad range of species which include 51 species from 39 genera of 21 families was obtained.45 species from 33 genera of 17 families in the the early lineage of angiosperms were chosen from the APG, and 6 species from 6 genera of 4 families from tha basal eudicots and gymnosperms as outgroups. The results are as follows:Amborellaceae,which was reputed as an primitive vesselless angiosperm, the vessel elements were discovered in the secondary xylem. The primitive end wall is the scalariform perforation plate. Nymphaeaceae,which was an aquicolous plant, had been considered as a secondarily vesselless by deduction. Recently, some papers have argued the vessel elements were existent in this family, The results in the present paper showed vessel elements were existent in some genera. Cabombaceae, which had been regarded as a secondarily vesselless as Nymphaeaceae. The vessel elements were found as same as some former discribes in our study. The perforation plates are simple. Schisandraceae,perforation plates are typically scalariform with 1-15-(30) bars, but some perforations are simple. Illiciaceae,as well as Trimeniaceae, both have perforation plates which are scalariform with numerous bars. Chloranthaceae,vessel elements are primitive with scalariform perforation plates with many bars. Sarcandra found the presence of vessels in the secondary xylem, although it was considered vesselless primatively and discovered in the primary xylem. Winteraceae,which is also an reputed vesselless angiosperm, the vessel elements with primitive scalariform perforation plates were observed in this paper. Atherospermataceae,perforation plates scalariform with different bars in different genera. Hernandiaceae,all perforation plates are simple. Lauraceae, with simple and scalariform perforation plates. Myristicaceae,some perforation plates are scalariform with few bars and some are simple. Magnoliaceae,perforation plates are scalariform, but occasionally are simple. Annonaceae, all perforation plates are simple as which in Piperaceae. Saururaceae, perforation plates are scalariform, but occasionally are reticulate. Ceratophyllaceae, there is no vascular bundle in the xylem. Trochodendraceae(basal Eudicots).which is an reputed vesselless angiosperm, were observed vessel elements. In this paper,the facticity was proved in low-vacuum because of some doubts still exit, and the vessels of the two genera in this family were compared. Proteaceae(basal Eudicots),perforations typically are simple. Pinaceae(Gymnosperm), vesselless as is known to all. Gnetaceae(Gymnosperm),perforations are simple.In order to stand up for the faticity of the results, the effect of SEM and SEM preparation on pit membrane remnants were also tested in this paper.In this study, more vessel informations about Austrobaileyaceae, Calycanthaceae, Monimiaceae, Eupomatiaceae and Aristolochiaceae were added, and then, there are 46 genera from 22 families in all from basal angiosperms and 4 families of outgroups. The author's observations lead to the following conclusions1)In the reputed primitively vesselless angiosperms, including Amborellaceae, Winteraceae, Trochodendraceae and Sarcandra, the vessel elements were observed. So, the groups possess vessels, and may be the groups ought to be named as original vessel angiosperms.2) Aquatics.The vessel elements with simple perforation plates were present in Cabombaceae and some genera of Nymphaeaceae. There is no vascular bundle in the xylem of Ceratophyllaceae.3)Tetracentron and other vesselless groups which were considered previously should be different ancestral to vessel-bearing angiosperms in different evolutionary ways of the vessels origin, and the Nymphaeales was probably by another way. So, there are multiple original of the vessels.4) Specializations of the perforation plates are accord with the evolution of these groups. Amborellaceae,Winteraceae and Sarcandra of Chloranthaceae may be a blind line of vessel specialization. And vesselless of Nymphaeaceae maybe primitive.5) The morphology of the vessel elements and perforation plates were different in families and genera (or species), so the differences may contribute to the classification.6)From scalariform perforation plates to simple, there are many evolutionary ways; reticulate-scalariform cannot make sure the direction of evolution. The transition from reticulate to simple was observed.and contributed to process of from reticulate perforation plate to simple.7) The vessel elements were very primitive in the secondary xylem of Amborellaceae. Austrobaileyales, scalariform perforation plates with numerous bars. The vessel elements were also primitive in Chloranthaceae, but more specialized than Amborellaceae and more primitive than Austrbaileyales. The vessel elements of Canellales were the same primitive as in Austrobaileyales. The perforation plates of vessel elements were similitude among Laurales, Magnoliales and Piperales. The diversification rates of the orders are almost accord with the levels of specialization of perforation plates. In conclusion, the appearing and evolution of vessel elements are the important reasons for what the angiosperms flourished in a short time.