<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
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
