Noninvasive measurement of plant water flow by nuclear magnetic resonance.

Water flow through the stem of an intact cucumber plant has been measured by using pulsed NMR. This method yields the linear flow velocity of the sapstream, found to be proportional to the loss of weight due to evaporation. The presence of a large excess of stationary water (for cucumber 95% of the total water content) does not interfere with the detection of a small amount of flowing water, due to cancellation of the NMR signal of stationary water. This makes the method particulary suitable for application to biological systems with a high stationary water content.