The root barrier to radial oxygen loss (ROL) is known as a root trait of many wetland plants, including rice, where it restricts oxygen loss from the root to the anoxic soil so that oxygen supply to the growing root tip is sustained. The barrier is believed to result from suberization and/or lignification in the cell walls of the root exodermis. We have recently discovered that the ROL barrier also restricts radial water loss and thereby possibly provides resistance to tissue desiccation during conditions of water deficit in the topsoil. Moreover, there is now experimental evidence that the ROL barrier can restrict radial intrusion of soil phytotoxins such as reduced iron and sulphide. Interestingly, the root ROL barrier in the Oryza genus is generally not constitutively present but is formed as a response to environmental signals. These signals include waste products from anaerobic bacteria in reduced soils but now also low soil water potential. The present talk presents highlights from our recent research with emphasis on the multiple functions of a suberized and/or lignified root exodermis and the contrasting environmental signals involved in formation of an inducible barrier. The talk will also analyse other key root traits such as root dimensions, the cortex to stele ratio and cortical aerenchyma and the importance of these for root acclimation to both too much and too little soil water.