<i><span style="font-family:"">Cycas angulata, Cycas armstrongii </span></i><span style="font-family:"">and<i> Cycas conferta </i>that are<i&g...<i><span style="font-family:"">Cycas angulata, Cycas armstrongii </span></i><span style="font-family:"">and<i> Cycas conferta </i>that are<i> </i>native species of Australia were collected in Darwin city of tropical region, <i>Zamia </i><i>erosa </i>and angiosperm <i>Guaiacum officinale</i> of Zygophyllaceae which are introduced collected in the Darwin Botanic Gardens, and were carried out light microscope and electron microscope observed research to tracheary element and parenchyma tissue cells of leaflet, rachis and stem. The results showed that there are more vessel elements in their xylems;the length of vessel element of Cycadaceae with Zamiaceae are not obvious difference, the length of vessel element of angiosperm <i>Guaiacum officinale</i> is shorter, but their diameter is smaller, we thought that the characteristics which the length of vessel element is longer and the diameter is bigger are more evolutionary, because thus vessel, their number which interconnected points of possessed perforations’ end walls of vessel element is fewer, and the passageway space is larger so that the conduction speed and quantity are faster and more in unit length range and unit time. These vessels are annular vessels, spiral vessels, scalariform vessels, reticular vessels, pitted vessels and scalariform-pitted vessels, etc. In the transverse section, the vessel elements of Cycadaceae and Zamiaceae are circular, polygonous, more similar to vessel characteristics of <a name="OLE_LINK73"></a>leaf and stem of some angiosperms;however, the number of circular vessel of <a name="OLE_LINK21"></a><i>Guaiacum </i><i>officinale</i> is more, about occupy 35%, others are polygonous. The diameter of vessel is that annular vessel, spiral vessel is least, scalariform vessel or scalariform-reticular vessel is medium, reticular vessel and pitted vessel are the biggest, the characteristic is same as angiosperm. In <i>Cycas conferta</i>, etc. plants often can see several large perforations in the end walls, some species are several big scalar展开更多
A recently discovered megafossil of whole plant cycad is briefly reported here. The specimen is collected from the Yangcaogou Formation (Upper Triassic) in Changheying, Beipiao, Liaoning. The whole plant is preserved ...A recently discovered megafossil of whole plant cycad is briefly reported here. The specimen is collected from the Yangcaogou Formation (Upper Triassic) in Changheying, Beipiao, Liaoning. The whole plant is preserved intact on a sandstone slab, 89 cm long and 130 cm wide, including leaves up to 82 cm long and a male cone physically attached to the stem apex. Analysis on the morphology, arrangement and venation of leaf and pinna, male cone and its relationship with other parts indicates that the fossil is closely related to living Zamiaceae in Cycadales. This cycad fossil is hitherto most completely preserved cycad specimen including both vegetative and reproductive organs. Its discovery contributes much to our understanding of the morphology and evolution of cycads, palaeoclimate as well as palaeoenvironment.展开更多
文摘<i><span style="font-family:"">Cycas angulata, Cycas armstrongii </span></i><span style="font-family:"">and<i> Cycas conferta </i>that are<i> </i>native species of Australia were collected in Darwin city of tropical region, <i>Zamia </i><i>erosa </i>and angiosperm <i>Guaiacum officinale</i> of Zygophyllaceae which are introduced collected in the Darwin Botanic Gardens, and were carried out light microscope and electron microscope observed research to tracheary element and parenchyma tissue cells of leaflet, rachis and stem. The results showed that there are more vessel elements in their xylems;the length of vessel element of Cycadaceae with Zamiaceae are not obvious difference, the length of vessel element of angiosperm <i>Guaiacum officinale</i> is shorter, but their diameter is smaller, we thought that the characteristics which the length of vessel element is longer and the diameter is bigger are more evolutionary, because thus vessel, their number which interconnected points of possessed perforations’ end walls of vessel element is fewer, and the passageway space is larger so that the conduction speed and quantity are faster and more in unit length range and unit time. These vessels are annular vessels, spiral vessels, scalariform vessels, reticular vessels, pitted vessels and scalariform-pitted vessels, etc. In the transverse section, the vessel elements of Cycadaceae and Zamiaceae are circular, polygonous, more similar to vessel characteristics of <a name="OLE_LINK73"></a>leaf and stem of some angiosperms;however, the number of circular vessel of <a name="OLE_LINK21"></a><i>Guaiacum </i><i>officinale</i> is more, about occupy 35%, others are polygonous. The diameter of vessel is that annular vessel, spiral vessel is least, scalariform vessel or scalariform-reticular vessel is medium, reticular vessel and pitted vessel are the biggest, the characteristic is same as angiosperm. In <i>Cycas conferta</i>, etc. plants often can see several large perforations in the end walls, some species are several big scalar
基金Supported by the National Natursl Science Foundation of China (Grant Nos. 40772006, 40372008, 40632010 and J0630967)Knowledge Innovation Program of the Chinese Academy of Sciences (Grant No. KZCX2-YW-154)National Basic Research Program of China (Grant No. 2006CB701401)
文摘A recently discovered megafossil of whole plant cycad is briefly reported here. The specimen is collected from the Yangcaogou Formation (Upper Triassic) in Changheying, Beipiao, Liaoning. The whole plant is preserved intact on a sandstone slab, 89 cm long and 130 cm wide, including leaves up to 82 cm long and a male cone physically attached to the stem apex. Analysis on the morphology, arrangement and venation of leaf and pinna, male cone and its relationship with other parts indicates that the fossil is closely related to living Zamiaceae in Cycadales. This cycad fossil is hitherto most completely preserved cycad specimen including both vegetative and reproductive organs. Its discovery contributes much to our understanding of the morphology and evolution of cycads, palaeoclimate as well as palaeoenvironment.
