© 2004 Heron Publishing—Victoria, Canada
Hydraulic conductivity and embolism in the mangrove tree Laguncularia racemosa
Frank W. Ewers (1, 2), Jórge Lopez-Portillo (3), Guillermo Angeles (3) and Jack B. Fisher (4)
1. Department of Plant Biology, Michigan State University, East Lansing, MI 48824-1312, USA / 2. Corresponding author (ewers@msu.edu) / 3. Instituto de Ecología, A.C., Apdo Postal 63, Xalapa 91070 Veracruz, México / 4. Fairchild Tropical Garden, 11935 Old Cutler Road, Miami, FL 33156, USA / Received January 22, 2003; accepted February 8, 2004; published online July 1, 2004
Summary
We measured xylem pressure potentials, soil osmotic potentials, hydraulic conductivity and percent loss of conductivity (PLC)
due to embolism, and made microscopic observations of perfused dye in the white mangrove tree, Laguncularia racemosa (L.) Gaertn. f., (1) to determine its vulnerability to air embolism compared with published results for the highly salt-tolerant
red mangrove tree, Rhizophora mangle L., and (2) to identify possible relationships between air embolism, permanent blockage of vessels and stem diameter. Laguncularia racemosa was more vulnerable to embolism than reported for R. mangle, with 50 PLC at –3.4 MPa. Narrow stems (5-mm diameter) had higher PLC than larger stems (8.4- or 14-mm diameter) of the same
plants. Basic fuchsin dye indicated that up to 89% of the vessels, especially in the narrow stems, had permanent blockage
that could not be reversed by high pressure perfusion. Air embolism could lead to permanent vessel blockage and eventual stem
mortality. Such vulnerability to embolism may restrict the growth of L. racemosa and limit its distribution to less salty areas of mangrove communities.
Keywords:
differential mortality of stems, nonconductive xylem, specific conductivity, vulnerability curve, white mangrove.
