天星蕨“隆孔”的发现及其可能的形态演化关系

Discovery of Christensenia assamica's“Raised Pore”and Its Possible Morphological Evolution

该研究通过石蜡切片及扫描电镜观察,首次报道了天星蕨(Christensenia assamica)叶片的通气结构即“隆孔”(raised pore),系维管植物新的通气结构类型。结果表明:(1)隆孔是位于叶片下表皮、由约20个条形细胞围成的、呈倒置碗状隆起,隆起的内壁密布微绒毛,隆起顶部有一个直径约为240μm、不能开闭的圆孔。(2)隆孔下方的气室内有表面密布微绒毛的、分支管状的光合细胞。(3)随气室向叶脉处过渡,微绒毛渐变为微纤丝、条状斑块。(4)隆孔与苔藓植物地钱类的单式气孔外形相似,但细胞分化远比后者复杂。研究认为,隆孔是目前在维管植物中发现的孔径最大、不能开闭、具有高效的气体代谢和特殊防御功能的通气结构,可能与苔藓植物地钱类的单式气孔具有一定的形态演化关系。

The feature of a new type of ventilatory structure in vascular plant named as the“raised pore”in Christensenia assamica's leaves were observed by using paraffin section and SEM for the first time.The results showed that:(1)the raised pore was comprised of around 20 strip cells,like a raised upside-down bowl on the outer epidermis under leaves,massive microvilli are distributed on the intine of the raised part,and there is a round hole on the top that cannot be opened or closed which diameter is about 240μm;(2)The photosynthetic cells liked tubular branches are contained in the air chamber under the raised pore and massive microvilli are distributed on them;(3)With the transition from the air chamber to the leaf vein,microvilli gradually changed into microfibrils and strip-like plaques;(4)The appearance of the raised pore is similar with hepatica's single stomata of bryophytes,but cell differentiation is more complicated than the latter.It is considered that the raised pore is a kind of ventilatory structure in vascular plant with the largest diameter found so far,can neither be opened nor closed,and has high efficiency in terms of gas metabolism and special defense function.It may be related to the morphological evolution of hepatica's single stomata of bryophytes.