Conducting tissue of leaves in Nageia and Podocarpus
2008
Sun Tongxing
The conducting tissue structure of transverse and longitudinal sections was observed on leaves of Podocarpus and Nageia. Results showed: in Podocarpus leaves, there is only one midrib, the xylem tracheid of midrib vascular bundle is multi-form, transfusion tissue belongs to Cycas-type and transfusion tracheids are isodiametric, the accessory transfusion tracheids between palisade tissue and sponge tissue are developed; in Nageia leaves, there are plenty of parallel leaves, the xylem tracheids of each vein are relatively simple, transfusion tissue belongs to Taxus-type and transfusion tracheids are longer in longitudinal section than that in transverse section, the accessory transfusion tissue between palisade tissue and sponge tissue is absent. Considering other differences that in leaves of Podocarpus there are three resin ducts under vascular bundle of midrib, mesophyll cells are differentiated into palisade tissue and sponge tissue; in leaves of Nageia, there is only one resin duct under vascular bundle in each vein and no obvious differentiation in mesophyll cells, palisade tissue can be found on both sides, and sclereids can also be found in mesophyll tissue. The anatomical differences of leaf veins and mesophylls between Nageia and Podocarpus mentioned above support the viewpoint that Nageia and Podocarpus are two independent genera.
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