田菁营养器官的解剖结构特征

运用石蜡切片法与组织离析法研究田菁营养器官解剖结构特征。结果表明，田菁根部显示典型的次生结构特征，内皮层具凯氏带；根表面有大量根瘤，根瘤菌分布在根部皮层，维管组织相连形成输导组织网。茎部表皮细胞壁出现角质层，皮层含有特化的厚角组织，由大型薄壁细胞构成，维管组织具有含晶韧皮纤维。茎瘤3～4个，大小不等且不连续分布，茎瘤外层为皮层，内层为含菌组织。叶片为异面叶，角质层与表皮层较厚，栅栏组织发达，近叶厚的1/2，海绵组织细胞间隙大，气孔小且多。田菁根、茎的木质部发达，有较多大孔径的导管及丰富的木纤维，叶片栅海比、组织结构紧密度(CTR)较大。田菁的解剖特点显示出其具有的固氮特性以及耐盐、抗旱的生态适应性。

Anatomical Features of Vegetative Organs of Sesbania cannabina

The anatomical structures of Sesbania cannabina vegetative organs were studied by paraffin and tissue segregation. The results showed that there were typical secondary structure characteristics of root of S. cannabina while there were casparian strip in the endoderm, a lot of nodules on the surface of root; rhizobia were distributed in the cortex of root, and its vascular tissue was connected to form a channel network. Cuticle appeared in epidermal cell walls of stem. There was specialized collenchyma in the cortex, which consisted of parenchyma cells. Vascular tissue had crystal phloem fiber. There were 3—4 stem nodules of different size, and distributing discontinuously. The outer layer of stem was cortex while the inner layer was bacteria tissue. The leaves were bifacial. The cuticle and epidermis of leaves were thick, and palisade tissues were well-developed, nearly half of leaf thickness. As for its sponge tissue, the intercellular space was large, and there were many small stomas. Xylems were rather rich in the root and stem of S. cannabina, with a number of large aperture vessels and rich wood fibers. Thickness rate of palisade and spongy and leaf palisade tissue tightness (CTR) were high. The anatomical features of S. cannabina showed its characteristics of nitrogen fixation and ecological adaptation of salt tolerance and drought resisting.