© 1994 Heron Publishing—Victoria, Canada
Formation and seasonal occurrence of xylem embolism in Alnus cordata
R. Tognetti (1) and M. Borghetti (2, 3)
1. Istituto Miglioramento Genetico delle Piante Forestali, Consiglio Nazionale delle Ricerche, via A. Vannucci 13, 50134 Firenze,
Italy / 2. Dipartimento di Produzione Vegetale, Università della Basilicata, via. N. Sauro 85, 85100 Potenza, Italy / 3. Author to whom correspondence should be addressed / Received April 6, 1993
Summary
We investigated the vulnerability of xylem to embolism and the seasonal occurrence of xylem embolism in Italian alder (Alnus cordata Loisel.) by acoustic and hydraulic methods. Wood anatomy was also studied. More than eighty percent of the vessels were less
than 50 mm long and no vessels were longer than 120 mm. Mean vessel diameter was 48 µm. Ultrasound acoustic emissions from
root and branch segments dehydrating in air followed a similar pattern: in both tissues, emission peaks were recorded when
the relative water content of the xylem was around 0.2. In branches dehydrating in air, xylem embolism increased linearly
as water potential decreased. In trees in the field, more than 80 percent of hydraulic conductivity was lost in the tree crowns
during winter. Recovery from winter embolism occurred mostly before bud burst. In summer, xylem embolism was low (< 30%) and
acoustic emissions from roots, stem and branches of trees in the field were also low.
Keywords:
acoustic emissions, cavitation, hydraulic conductivity, Italian alder.
