Internal winds in water lilies: an adaptation for life in anaerobic sediments.

The network of internal gas spaces in the yellow water lily constitutes a pressurized flow-through system which forces oxygen to the roots and rhizome buried in the anaerobic sediment. By the purely physical processes of thermal transpiration and hygrometric pressure, several liters of air per day enter the young, newly emerged leaves of Nuphar luteum against a small pressure gradient. This air moves en masse down the petioles of the young leaves (at rates up to 50 centimeters per minute) to the rhizome, forcing a simultaneous flow of gas (rich in carbon dioxide) from the rhizome up the petioles of the older emergent leaves to the atmosphere. The ventilation system has important physiological and ecological consequences.