Water balance in Cucumis plants measured by nuclear magnetic resonance. 2.

Nuclear magnetic resonance (NMR) was used to investigate the effects of changes in root temperature, of changes in the area of root in contact with culture solution and of day/night rhythm on the water balance of a cucumber and a gherkin plant. Results are discussed in terms of water potential, flow rate and resistance using a previously presented model of water balance. As long as water uptake alone is varied, flow rate and water content (or potential) will change in the same direction. In contrast, from that model it is predicted that changes in transpiration will affect flow rate and water content in opposite ways. An experimental verification of this prediction was given in the previous paper. Results obtained by the NMR method are compared to those determined using a dendrometer. The results demonstrate that the NMR method is a valuable tool to study plant water balance and that it can serve as a technique for discriminating between changes in plant water balance that are due to changes in water uptake by roots and those due to changes in transpiration.