Structural Characteristics of Vessels in Three Families of Cycadopsida  

作　　者：Yuyuan Huang Wenbo Liao Xiaoqing Zhong Lijun Wei Hongda Zhang Yuanfeng Lu 

机构地区：[1]College of Life Sciences, Zhongkai University of Agriclture and Technology, Guangzhou 510225, China [2]School of Life Sciences, Sun Yat-sen University, Guangzhou 510275, China [3]Guangxi Subtropical Institute of Crops, Nanning 530001, China [4]Guangxi Institute of Botany, Chinese Academy of Sciences, Guilin 541006, China [5]Agricultural College, Guangxi University, Nanning 530005, China

出　　处：《Journal of Life Sciences》2010年第7期1-15,共15页生命科学（英文版）

基　　金：There are 8 projects supported by National Natural Science Foundation of China which Dr. Y.Y. Huang have taken charge of and/or taken part in; Dr. Y.Y. Huang have published 5 bookmakings and more than 100 papers.

摘　　要：The pinna of Cycasferruginea F.N. Wei （Cycadaceae）, pinnas or rachises ofStangeria eriopus （Kune） Baill. （Stangeriaceae）, Dioon holmgrenii De Luca, Sabato ＆ Vazq. Torres, Macrozamia moorei F. Muell. ex C. Moore （Zamiaceae） were macerated and dissociated by Jeffrey＇s technique, rinsed with water, dehydrated and gold-plated for observation with scanning electron microscopes. The results showed that the pinna and rachis of the leaf tissues of the four cycad species possess many vessel elements and a few tracheid elements in the conducting tissue of the xylem. Annular, spiral, scalariform, pitted and reticulate vessels and some transitional types, including scalariform-pitted, scalariform-reticulate and reticulate-pitted vessels, were observed in the conducting tissues. The characteristics of the vessels of each species, and the evolutionary relation of four genera of cycads were analyzed. Compared with those of angiosperms, the structural characters of vessels of cycad are at the moderate level of evolution and more advanced than some primitive taxa of angiosperms and ferns. Vessels have been discovered in many genera of ferns, which are even more primitive than cycads. In many ferns, only vessel elements, but no tracheids are found in vascular tissue. In the present study, the authors discovered vessels in different genera of three families ofcycads which showed that the existence of vessels in primitive plant taxa is a widespread phenomenon. Vessel elements in vascular tissues of cycads have probably allowed cycads to adapt to various environmental stresses and enabled their persistence over their long evolutionary history. Cycads are the most primitive of the extant seed plants and the widespread existence of vessels in the group has broad implications for plant systematics, evolution and comparative morphology.

关 键 词：ADAPTABILITY CYCADS EVOLUTION structural characteristic VESSEL scanning electron microscopes. 

分 类 号：Q944.5[生物学—植物学] TS976[轻工技术与工程]