Early changes of water diffusional transfer in maize roots under the influence of water stress

The time dependent response of the hydrodynamic root system to PEG-induced water stress was studied in intact maize Zea mays L. seedlings at intervals varying from several seconds to 3 h by detecting diffusional water transfer with the use of pulsed NMR. In order to establish the contribution of water transfer through aquaporins in response to water stress, the transmembrane water transport in control roots and roots treated with aquaporin blocker was detected. Changes in diffusional water transfer under stress were shown to depend on the duration of osmotic treatment, and include the series of heterogeneous processes. A transient pulsed jump in diffusional water transfer detected several seconds after beginning the osmotic treatment is associated with the spread of the wave of hydraulic pressure along the root. It is proposed that early responses of the hydrodynamic system of maize roots to PEG-induced water stress lies in the unequal change in water permeability of the plasmalemma and tonoplast resulting from the changes in aquaporin activity and perhaps in the escalation of water transfer along the cell vacuome.

► Root response to water stress consists of a series of time- dependent stages.
► Early response includes unequal changes in plasmalemma and tonoplast permeability.
► Pulsed jump in diffusional water transfer preceded changes in membrane permeability.