Water uptake resumption following soil drought: a comparison among four barley genotypes

Abstract

Soil water resulting from episodic growing season rainfall evaporates rapidly in semi-arid regions. Plants may mnot benefit from such water additions if near-surface roots are unable to resume water uptake rapidly following periods of soil water deficit. Our objectives were to develop a means of quantifying root uptake responses in the upper soil layer following rewetting after soil water deficit, and to evaluate the existence of genotypic differences among four diverse barley (Hordeum vulgare L.) genotypes in this regard. Plants were grown in replicate soil columns having hydraulically isolated surface and subsoil layers, and instrumented with time-domain reflectometry (TDR) waveguides. The upper 0.05 m soil layer was allowed to dry to —1.8 to —3.0 MPa for 10-14 d, during which time subsoil wetness was maintained at about —0.6 to —0.7 MPa. The time-course of soil water uptake was monitored at 0.5 h intervals following rewetting of the surface layer. Substantial water uptake began 1 d after rewetting following 10 d, and 2-3 d after rewetting following 14 d of water deficit. Rate of water uptake was more rapid in response to a second rewetting 5-7 d later. Consistent genotypic responses in terms of cumulative water uptake on a whole plant and leaf area-specific basis were observed during each trial. These results have application to evaluating drought hardiness and interspecific competitive ability under semi-arid conditions, and to investigations of root physiological and morphological changes that contribute to recovery from water deficit