TITLE:
Comparative Studies of Tracheary Element Structure of Some Gymnosperms with Angiosperms
AUTHORS:
Yuyuan Huang, Yanhua Han, Lijun Wei, Jiazhuo Wang
KEYWORDS:
Adaptability, Gymnosperm, Angiosperm, Evolution, Vessel, Structural Characteristics
JOURNAL NAME:
American Journal of Plant Sciences,
Vol.8 No.5,
April
17,
2017
ABSTRACT: Tissues of the pinna and
rachis of Cycas diannaensis and pinna, rachis, and root of Cycas taiwaniana,
rachis of Cycas szechuanensis, stem of Metasequoia glyptostroboides (Taxodiaceae), stems of Chamaecyparis obtusa (Sieb.et Zucc.) Endl
cv. Tetragona (Cupressaceae), and
leaves and stems of Michelia alba and Michelia figo and stems of Amygdalus persica (angiosperms) were compared using the scanning electron microscopy. In all species of
these gymnosperms, their many tracheary elemnts have perforations in end walls
and lateral walls. These
structures are the same as vessels of angiosperms; therefore, these tracheary elements
are vessel elements. Many types of vessels were found in cycads: pitted vessels
in M. glyptostroboides, spiral and pitted vessels in Chamaecyparis obtusa cv. Tetragona. The development and structural characteristics of vessels of cycads, the
two other gymnosperms, and the angiosperms were identical. Some characters such
as extent of incline of perforation plate in the end wall showed that vessel
characters of some angiosperms were more primitive than the cycads or M. glyptostroboides and C. obtusa cv. Tetragona. Many of the vessel elements of the angiosperms were band shaped,
without end walls, and had only two lateral walls and other two margins; the end was acuate or with an arc
margin; the
end of some vessel elements was acute with no perforations, many perforations located only in lateral
wall. Such results are rarely reported in previous work. In all species, perforations
were seen only in tracheae, and the walls of parenchyma cells only had a thin
primary wall and without perforation. Analysis and discussion to the experimental measures which were observed and research of the structure of vessel or
tracheid, pointed out that several measures all could be used and the Jeffrey’ method effects were better. Comparing the vessels of
cycads, Taxodiaceae and Cupressaceae helps us to understand the mechanism in which these most primitive
or more primitive extant gymnosperms were adapted to harsh environments and to understand these species’ evolutionary extent, and has the significance to the studies of plant anatomy, plant
systematics and plant evolution.