| Abstract: | Soil water resulting from episodic growing season rainfall evaporatesrapidly in semi-arid regions. Plants may mnot benefit from suchwater additions if near-surface roots are unable to resume wateruptake rapidly following periods of soil water deficit. Ourobjectives were to develop a means of quantifying root uptakeresponses in the upper soil layer following rewetting aftersoil water deficit, and to evaluate the existence of genotypicdifferences among four diverse barley (Hordeum vulgare L.) genotypesin this regard. Plants were grown in replicate soil columnshaving hydraulically isolated surface and subsoil layers, andinstrumented with time-domain reflectometry (TDR) waveguides.The upper 0.05 m soil layer was allowed to dry to —1.8to —3.0 MPa for 10-14 d, during which time subsoil wetnesswas maintained at about —0.6 to —0.7 MPa. The time-courseof soil water uptake was monitored at 0.5 h intervals followingrewetting of the surface layer. Substantial water uptake began1 d after rewetting following 10 d, and 2-3 d after rewettingfollowing 14 d of water deficit. Rate of water uptake was morerapid in response to a second rewetting 5-7 d later. Consistentgenotypic responses in terms of cumulative water uptake on awhole plant and leaf area-specific basis were observed duringeach trial. These results have application to evaluating droughthardiness and interspecific competitive ability under semi-aridconditions, and to investigations of root physiological andmorphological changes that contribute to recovery from waterdeficit Key words: Hordeum vulgare, root water uptake, soil water deficit, time-domain reflectometry |
