菱的丝状结构是沉水叶还是同化根?--植物学教材质疑(四)

Are the Filiform Organs Submerged Leaves or Photosynthetic Roots in Trapa natans?Questioning Botany Textbooks(Ⅳ)

异形叶性是植物界常见现象之一。有的植物学教材以菱为异形叶性的例子,并指出,“菱的浮水叶扁平呈菱形,而沉水叶却细裂呈丝状”。但是,也有文献认为,这些“沉水丝状器官”是同化根或变态托叶。菱的形态和解剖结构均显示,这些“沉水丝状器官”是生于沉水茎上的不定根,不定根上再发出许多丝状侧根,这些侧根是具同化功能的变态器官。根据本研究,笔者设计并实施了一个探究性植物实验,以期培养学生的探究能力以及批判性思维习惯和能力。

Many plant species have the ability to alter their leaf morphology in response to different envi-ronments.This phenomenon is termed heterophylly.Some textbooks of botany took Trapa natans L.as an exam-ple of heterophylly,and stated that its floating leaves are rhombic while submerged leaves are finely,pin-nately divided.However,observations on the morphology and anatomy of T.natans indicated that the sub-merged filiform organs are adventitious roots with many lateral roots,and these lateral roots are modified or specialized organs with the function of photosynthesis.Herein,an exploratory experiment was designed to investigate whether the submerged filiform organs of T.natans are leaves,roots or modified stipules.This ex-periment can also improve the students’inquiring ability and critical thinking habit and skills.