Into the voids: The distribution, function, development and maintenance of gas spaces in plants

Gas spaces are a common but frequently overlooked component of most embryophytes, and of several brown macroalgae. They have many functions, but in vascular land plants the predominant Function is that of gas distribution. In aquatic macrophytes buoyancy is a significant function of gas spaces. The development of gas spaces can occur without contact with an external gas phase. Schizogenous gas spaces develop within tissues by mechanisms which involve pre-programmed separation of middle lamellae at the corners of cells, frequently followed by more widespread separation. In both cases there is replacement of the resulting vacuum plus water vapour with gases which were dissolved in the water of adjacent cells. Lysigenous gas spaces are produced in a similar way but with cell lysis following and perhaps replacing separation of middle lamellae, and the need for removal of water and solutes into adjacent cells. Maintenance of gas spaces involves a combination of absence of invasion with liquid water and maintenance of hydrophobic surfaces around the gas spaces. This glib summary of the formation and maintenance of gas spaces covers many aspects of these phenomena which need Further investigation. (C) 1996 Annals of Botany Company