泽米科植物羽片脉序和解剖学及其系统学意义

摘要

Pinna venation and pinna anatomy were examined in ten species of six genera of Zamiaceae (Cycadales), which represent all four tribes. Pinna venation consists of dichotomous parallel veins without a midrib. The vein endings connect to each other in different forms in Dioon spinulosum, Encephalartos friderici_guilielmii and Macrozamia moorei, while they are never connected and reach the pinna margin in Lepidozamia peroffskyana, Ceratozamia mexicana var. robusta, C. hildae, Zamia muricata, Z. debilis, Z. furfuracea and Z. floridana, and gradually fade out in L. peroffskyana, C. mexicana var. robusta, and C. hildae. In transverse section, pinna generally consists of an adaxial epidermis and an abaxial epidermis, hypodermal sclerenchyma and mesophyll which may be differentiated into distinct adaxial and abaxial palisade regions, or adaxial palisade only, or entirely spongy tissue. However, typical spongy parenchyma and transfusion tissue are absent from this family. Mucilage canals are opposite the vascular bundles in D. spinulosum, or alternate with vascular bundles in E. friderici_guilielmii, L. peroffskyana and M. moorei. Girder sclerenchyma is connected with the abaxial epidermis only in C. mexicana var. robusta and C. hildae, but with both adaxial and abaxial epidermis in Z. muricata, Z. debilis, Z. furfuracea and Z. floridana. Pinna venation and anatomy support Stevenson's classification of Zamiaceae into two subfamilies.%研究了苏铁目泽米科Zamiaceae 2亚科的所有4族(Stevenson系统, 1992)共10种代表植物的羽片脉序及解剖学特征,结果显示泽米科羽片脉序为二歧分叉的平行脉,无中脉.小刺双子铁Dioon spinulosum、大头非洲铁Encephalartos friderici_guilielmii和摩尔大泽米Macrozamia moorei等的平行脉末端以不同的形式互相连接,而鳞木铁Lepidozamia peroffskyana、粗壮角果铁Ceratozamia mexicana var. robusta、竹叶角果铁C. hildae、佛州泽米Zamia floridana、柔叶泽米Z. debilis、鳞秕泽米Z. furfuracea和短尖泽米Z. muricata等的平行脉末端不连接而直达叶缘,其中鳞木铁、粗壮角果铁和竹叶角果铁的脉达叶缘后逐渐消失.羽片的横切面结构通常由表皮、下皮厚壁细胞和叶肉组成,表皮层包括上、下表皮各一层,叶肉可能同时分化出近上表面的栅栏组织和近下表面的栅栏组织,或仅有近上表面的栅栏组织分化,或无栅栏组织分化而完全为海绵组织.然而,泽米科没有典型的海绵组织和传输组织分化.小刺双子铁、大头非洲铁、鳞叶木铁和摩尔大泽米的羽片具有粘液道而无工字厚壁组织,在小刺双子铁中粘液道与维管束对生,在另3种中则与维管束轮生;但粗壮角果铁、竹叶角果铁、佛州泽米、柔叶泽米、鳞秕泽米和短尖泽米的羽片则具有工字厚壁组织而没有粘液道,其中粗壮角果铁和竹叶角果铁的羽片工字厚壁组织仅与上表皮相连,而佛州泽米、柔叶泽米、鳞秕泽米和短尖泽米的羽片工字厚壁组织与上、下表皮都相连.羽片脉序和解剖学特征支持Stevenson将泽米铁科分为两亚科的观点.