两种珙桐叶片结构的观察

珙桐(Davidia involucrata Baill.)与它的变种光叶珙桐[Davidia involucrata Baill.var.vilmoriniana(Dode)Wanger.]叶下表皮(即远轴面)差异较大,前者叶下表皮密被淡黄色或淡白色丝状单细胞粗毛,后者叶下表皮无毛或仅叶脉处被稀疏单细胞短毛或丝状粗毛。两者结构基本相似,表皮均由一层细胞构成,气孔仅分布在下表皮,无一定排列方向,为无规则型。叶肉具明显栅栏组织和海绵组织,是典型两面叶。叶脉的机械组织为腔隙厚角组织,维管组织韧皮部位于远轴面,木质部位于近轴面,两者间具形成层。

OBSERVATION OF THE LEAF STRUCTURE OF TWO DAVIDIA INVOLUCRATA BAILL SPECIES

The lower epidermis (far-axial surface )of Davidia involucrata Baill. and thaf of its variant, Davidia invotucrata Baill. var. vilmoriniana(Dode)Wanger have a significant difference. The lower epidermis of the former species was densely covered by light yellow or light white thick single-cell hair, but on that of the later variant, there was no hair or in the vein there were sparse short single-cell hair or filiform thick hair. The leaf structures of these two plants were basically alike: their epidermis were made up of one layer cells. Stomatas only existed disorderly on the lower epidermis and their arrangement was a irregular type. The mesophyll of their leal had distinct palisade tissue and spongy tissue, so the leaf was a typical bifacial leaf. The mechanical tissue of their vein was composed of laeunate collenchyma. The xylem and phloem of their vascular tissue were close to the near-axial and far-axial surface of the leaf respectively. Cambium was located between the phloem and xylem.