| 英文摘要 |
Fabaceae is one of the important families of flowering plants that play a crucial role in the human diet. Besides imperative sources of proteins, folk and traditional medicine, several species are sources of commercially important timbers. However, the wood anatomy of timber trees of the family has been studied extensively but information on climbing members is relatively neglected. The stem anatomy of Canavalia cathartica Thouars, and C. gladiata (Jacq.) DC. and Pueraria tuberosa (Roxb. ex Willd.) DC. was investigated histologically in the present study. In all three species, a single ring of the vascular cambium remained functional throughout the growing period and showed a regular growth pattern like most eudicots. As the plants grew (10- 12 mm thick stems), thin-walled xylem parenchyma formed at the beginning of the secondary growth underwent dedifferentiation and formed isolated or group of interxylary sieve elements. Subsequently, more and more adjacent parenchyma produced sieve elements, which resulted in the formation of interxylary phloem islands of various sizes and shapes. In 20–22 mm thick stems of all three species, the non-lignified, thin-walled xylem parenchyma adjacent to these islands divided repeatedly and formed radial files of meristematic cells, referred to as interxylary cambium. These segments of the interxylary cambium had irregular orientation (radial, tangential or diagonal) and exclusively produced phloem elements. The secondary xylem was diffuse-porous with indistinct growth rings and composed of dimorphic vessels, tracheids, and axial and ray parenchyma cells. Small vessels were arranged in clusters while wide vessels were solitary with vasicentric thick-walled lignified parenchyma. |
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