Water-Stress Patterns in Honey Mesquite

Haas, R.; Dodd, J.

Water stress (LWP) was measured in honey mesquite, _Prosopis glandulosa var. glandulosa_ (Torr.), trees by using the pressure chamber method to detect negative hydrostatic pressure in the xylem of leaf petioles. the method was sufficiently sensitive to measure short term changes of +/-1 bar LWP throughout the dirunal period. Mean differences between sun-exposed and shaded leaves averaged 4.7 bars LWP on a clear day in May. Although the mean LWP for five trees ranged from 15.8 to 18.1 bars LWP, the interaction of exposure and tree was relatively minor in comparison with the large diurnal differences in LWP. Diurnal changes in LWP, often greater than 20 bars, were associated with changes in the evaporative potential of the atomosphere. Total daily water stress and net daily water stress were calculated by integrating the area under a curve formed by the periodic measurements of LWP during the dirunal period. Net daily water stress was more sensitive to changes in enironmental variables than other daily summaries. Throughout the range of available soil mositure there was a close relationship between net daily water stress and the integrated evaporative potential on a daily basis.

Water-Stress Patterns in Honey Mesquite

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