短叶罗汉松叶结构的发育过程研究

短叶罗汉松叶的发育起始于茎端侧面分生组织区细胞分裂形成的叶原基。在叶的发育过程中,维管束下方的3个树脂道最先分化发育,然后,维管束内的原生木质部由近轴面向远轴面分化发育,同时原表皮下的一层薄壁细胞发育形成厚壁组织纤维,起支持幼叶的作用。当木质部基本成熟时,转输组织和韧皮部以及副转输组织开始发育,最后,叶肉组织分化发育为发达的栅栏组织细胞和海绵组织细胞。在叶内部结构分化发育的同时,表皮细胞的外侧形成较厚的角质层。在短叶罗汉松叶的结构中,发达的栅栏组织和角质层对于其生长在干旱和寒冷地区进行光合作用和蒸腾作用具有极为重要的意义。

Structure Development of the Leaf of Podocaarpus macrophyllus var. maki Endl.

The leaf development of Podocaarpus macrophyllus var.maki Endl.starts from leaf primordium which comes from the cell division of meristem zone in stem apex.Three resin ducks under the vascular bundle of leaf were differentiated and developed firstly,then the protoxylem in vascular bundle was differentiated from adaxial side to abaxial side.At the same time,the parenchyma cells under the protoderm were developed into fiber to support the leaves.When xylem was nearly matured,transfusion tissues,phloem and accessory transfusion tissues came into differentiation.Finally the mesophyll tissue was differentiated into palisade and spongy parenchyma.While the inner structures of leaf were differentiated and developed,the thick cuticle covering epidermal cells was also formed.In the leaf structures of Podocaarpus macrophyllus var.maki Endl.,multi-layer palisade cells and thick cuticle were very important to maintain normal photosynthesis and transpiration in dry and cold areas.