在水生植物中，是没有栅状叶肉细胞的，所以有很多胞间隙(气室)以增加浮力。

In aquatic plants, the palisade cells are absent so that there is more intercellular Spaces (air Spaces) for buoyancy.

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一般是经由鳃呼吸。大部分硬骨鱼有鳔，这是源于消化管的憩室，司控制浮力或为辅助呼吸器官。

Fish generally respire through gills. most bony fish es have a swim bladder a gas-filled organ used to adjust swimming depth.

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