Background Hard red winter wheat (HRWW; Triticum aestivm L.) plants from genotypes selected in the Northern Great Plains of the U.S. have less tissue water after exposure to cool autumn temperatures than plants from the Southern Great Plains. It is generally assumed that the reduced tissue water content of northern compared to southern cultivars is due to an impedance to water uptake by northern plants as a result of the low autumn temperatures. We hypothesize that if low temperature impedes water uptake then less soil water would be removed by northern than by southern-selected cultivars. This hypothesis was tested by comparing plant water uptake of a northern (FR) and a southern (FS) cultivar in relation to their foliage water content at 2°C.

      Results
      At 2°C foliage water content of FR plants decreased more rapidly than that of FS plants, similar to field results in the fall. During 6 wk, foliage water content of FR plants decreased 20 to 25% of the pre-treatment value, compared to only 5 to 10% by FS plants. Plant water uptake was about 60 g H2O·g FDW-1 by FS plants, while FR plants maintained plant water uptake in excess of 100 g H2O·g FDW-1 during the 6 wk period at 2°C. When four other northern genotypes of equal freeze resistance were studied, foliage water content and plant water uptake change were similar to FR plants.


      Conclusion
      In these northern-selected HRWW cultivars foliage water content reduction resulting from cold acclimation is not due to impedance to plant water uptake.