荔枝、龙眼及龙荔的茎解剖结构比较

为了观察荔枝、龙眼和龙荔茎解剖结构的异同,采用徒手切片法和组织离析法,对荔枝、龙眼和龙荔20份材料的茎横切面结构和导管分子的特征进行了比较研究。结果表明：（1）各试材的茎横切结构由外到内依次为：周皮、皮层、维管组织、髓和射线,但其结构特征总体上差异较大;龙眼种质的平均髓率（26.19%）显著高于龙荔（22.43%）和荔枝（6.96%）,各试材间,褐毛荔枝的髓率最小（3.37%）,‘三月红’居中（14.14%）,野生龙眼最大（30.27%）;荔枝的树皮率（41.93%）显著大于龙眼（33.21%）和龙荔（29.83%）。（2）各试材的导管密度未见明显规律,以‘三月红’的导管密度最小（93.17 个/mm2）,龙荔次之,为101.78 个/mm2;荔枝的导管总面积/木质部面积的比值显著大于龙眼和龙荔;‘三月红’的射线宽度（22.13 μm）显著大于其它试材。（3）20份试材的导管分子绝大多数属于孔纹式或网纹式,极少数为环纹式或螺纹式或梯纹式;‘三月红’的导管分子内径（35.97 μm）显著大于其它试材,龙荔次之（33.90 μm）;褐毛荔枝的导管分子（238.52 μm）显著长于其它试材。（4）导管分子短、孔径大、端壁倾斜度小（或水平）、无尾、孔纹、单穿孔板均是导管分子进化的特征;在荔枝试材中,‘三月红’的导管分子较为进化,而褐毛荔枝则较为原始。（5）对茎结构特征指标进行聚类分析,结果显示,20份试材首先聚为2大类,荔枝12份试材（除‘三月红’外）聚为第1大类;龙眼6份试材、龙荔及荔枝‘三月红’聚为第2大类;在这2大类的基础上又分为8个组,各组均有独自的显著特征。对荔枝、龙眼和龙荔3类植物茎结构特征的比较可知,总体上荔枝比龙眼原始,而龙荔居荔枝和龙眼之间。

Comparisons of Stem Anatomical Structures among Litchi,Longan and Longli

To observe similarities and differences in stem anatomical structures among litchi, longan and longli, we compared the stem transverse structures and vessel elements of 20 different materials among litchi, longan and longli by free hand section and tissue segregation procedure, respectively. The results showed that （ 1 ） The stem structure of the experimental materials from the inside to the outside was periderm, cortex, vascular tissue, pith and ray, but their structure characteristics exhibited great differences. Average pith rate of longan germplasm （26.19%） was significantly greater than that of longli （22. 43%） or litchi （6. 96%） germplasm, and among them the lowest pith rate was found in Litchi chinensis vat. fulvosus （3.37%）, followed by ＇ Sanyuehong＇ （ 14.14%）, and wild longan （30.27%）. In addition, the bark rate of litchi （41.93%） was significantly greater than that in longan （33.21%） and longli （29.83%）. （2） Vessel density of each tested material was not obviously regular, with ＇Sanyuehong＇ （93.17 No./mm2） exhibiting minimum vessel density, followed by longli （ 101.78 No./mm2） ; total vessel area/xylem area of litchi was significantly higher than that of longan and longli; the ＇Sanyuehong＇ （22.13 μm） ray was significantly wider than that of the other tested materials. （3） Vessel elements mostly belonged to pitted or reticulate vessels, but did include a few ringed, spiral or scalariform vessels in the 20 accessions. Vessel diameter of ＇Sanyuehong＇ （35.97 μm） was significantly higher than that of the other tested materials, followed by longli （33.90 μm）, with and L. chinensis var. fulvosus （238.52μm） significantly longer than other specimens. （4） The vessel elements of large aperture, short, end wall of small inclination （or level ）, no tail, pitted pattern, and simple perforation plate were evolutionary vessel element traits. In litchi germplasm, the vessel elements of ＇ Sanyuehong＇ were evolutionary,