Hydraulic signals in long-distance signaling.

Higher plants are sessile organisms that continuously adapt their metabolism and development in response to a changing environment. Control of water uptake and the maintenance of water status are key for the survival and optimal growth of plants. Environmental factors such as radiation, air temperature, rainfall, and humidity have a high impact on plant water relations. Hence, plants require a coordinated and timely response in above-ground and below-ground organs to cope with the changing need to take up and preserve water. In this review we will focus on changes in plant water availability and on how information on the water status is communicated to remote plant organs. We will summarize the current knowledge of long-distance signaling by hydraulic cues and of potential sensors required to convert a physical signal into a chemical messenger, namely the plant hormone abscisic acid (ABA).