杜鹃花属映山红亚属植物叶表皮显微形态特征及其分类学意义

Leaf epidermal micromorphological features of Rhododendronsubg. Tsutsusi (Ericaceae) and their taxonomic significance

为澄清映山红亚属(Rhododendron subg.Tsutsusi)内的系统关系问题,该研究选择杜鹃花属映山红亚属37种植物作为对象,其中29种为首次报道,通过扫描电镜观察其叶表皮显微特征。结果表明:(1)气孔器均为无规则型且均在远轴面。(2)根据叶片微形态特征将映山红亚属的种类分为杜鹃型(R.simisii-type)、岭南杜鹃型(R.mariae-type)、皋月杜鹃型(R.indicum-type)、崖壁杜鹃型(R.saxatile-type)及丁香杜鹃型(R.farrerae-type)5种类型。(3)杜鹃型植物的气孔器周边无或具间断的条形突起。(4)岭南杜鹃型植物的气孔器周围有多层条形突起环绕,保卫细胞两极不具T型加厚。(5)皋月杜鹃型植物的叶表皮保卫细胞两极具有T型加厚,与叶状苞亚属(Subg.Therorhodion)叶状苞杜鹃(R.redowskianum)的气孔器特征相似,推测其与叶状苞亚属具有一定的亲缘关系。(6)崖壁杜鹃型植物的叶表皮毛单一,多呈卷曲状,与其他类型有所不同且未见腺体。(7)丁香杜鹃型植物的叶表皮仅有腺体。(8)依据叶表皮微形态特征讨论了一些近缘种类的关系,如倾向于将背绒杜鹃(R.hypoblematosum)和千针叶杜鹃(R.polyraphidoideum)处理为独立的种,支持保留紫薇春(R.naamkwanense var.cryptonerve)作为南昆杜鹃(R.naamkwanense)的变种地位,不支持将腺花杜鹃(R.adenanthum)并入细瘦杜鹃(R.tenue)作异名处理等。该研究结果表明叶表皮显微特征在映山红亚属内物种划分上具有重要价值。

In order to clarify the relationships in Rhododendron subg.Tsutsusi,micromorphological characters of leaf epidermis were examined for 37 species in Rhododendron subg.Tsutsusi using scanning electron microscopy(SEM),among which the relevant features of 29 species are reported for the first time.The results are as follows:(1)The stomatal apparatus are anomocytic and all on abaxial surface.(2)According to the micromorphological features of glands,trichome types and stomatal apparatus of leaf epidermis,subg.Tsutsusi can be divided into five types,i.e.,R.simsii-type,R.mariae-type,R.indicum-type,R.saxatile-type and R.farrerae-type.(3)The plants in R.simsii-type have the similar morphological features,have no or discontinuous ringed striates around stomatal apparatus.(4)The plants in R.mariae-type do not have distinct T-pieces at the polar regions of guard cells but have multilayer ringed striates.(5)It is implied that the plants in R.indicum-type have the close affinity with subg.Therorhodion in having distinct T-pieces at the polar regions of guard cells.(6)R.saxatile-type differs from other types in its simple trichomes being virgate but without glands.(7)The leaf epidermis of R.farrerae-type has glands only.(8)The relationships between the closely related species are also discussed on the basis of leaf epidermal micromorphological features.For example,R.hypoblematosum and R.polyraphidoideum tend to be treated as separate species.Support the preservation of R.naamkwanense var.cryptonerve as a variety of R.naamkwanense,and do not support the R.adenanthum into R.tenue as a synonym.The results of this study show that micromorphological features of leaf epidermis are of significant value for species delimitation in subg.Tsutsusi.