Water relations and hydraulic architecture of peach trees under drought conditions

In this study we analyzed the vulnerability to embolism and the hydraulic architecture of peach trees. This species was particularly vulnerable to embolism. Vulnerability curves, established in the laboratory by introducing artificial embolism by application of positive pressure, showed that embolism significantly developed in stems when xylem water potentials felled below -1.5MPa and were fully embolised at -3.0MPa. Fifty percent loss of hydraulic conductivity was obtained when xylem water potentials became lower than 2.0MPa. At this point, the stomatal conductance was just reduced to 40 % of its maximal. In the field, under drought conditions, we measured significant degrees of embolism in stems, although stem embolism was limited by leaf fall. After irrigation, stem embolism was not repaired. We also analyzed the impact of new shoot formation on tree hydraulic architecture.