Abstract:The permeability of knotgrass (Paspalum distichum) experiment results showed the exodermis, cuticle and apoplastic barriers in nodes blocked the berberine tracer. The mechanical tissue in stems included the peripheral mechanical ring, sclerenchyma ring, vascular tissue system, and the honeycomb-like collenchyma in the pith and cortex. Air space in stems consisted of honeycomb in the pith and cortex, and aerenchyma in the nodes. The apoplastic barriers included in the inner, outer and vascular tissue system on the internodes, and around the nodes are prevented structures. Overall, the perfect mechanical tissue, air space, apoplastic barriers and its blocked property are the key structures of knotgrass adapted to wetland environment.