title: A survey of root pressures in vines of a tropical lowland forest.
abstract: Pre-dawn xylem pressures were measured with bubble manometers attached near the stem bases of 32 species of vines on Barro Colorado Island, Panama, to determine if pressures were sufficient to allow for possible refilling of embolized vessels. Of 29 dicotyledonous species 26 exhibited only negative xylem pressures, even pre-dawn during the wet season. In contrast, three members of the Dilleniaceae exhibited positive pre-dawn xylem pressures, with a maximum of 64 kPa in Doliocarpusmajor. A pressure of 64 kPa is sufficient to push water to a height of 6.4 m against gravity, but the specimens reached heights of 18 m. Thus, in all 29 dicotyledons examined, the xylem pressures were not sufficient to refill embolized vessels in the upper stems. In contrast, two of the smaller, non-dicotyledonous vines, the climbing fern Lygodiumvenustrum and the viny bamboo Rhipidocladumracemiflorum, had xylem pressures sufficient to push water to the apex of the plants. Therefore, a root pressure mechanism to reverse embolisms in stem xylem could apply to some but not to most of the climbing plants that were studied.
authors.affiliation: Department of Botany and Plant Pathology, Michigan State University, East Lansing, Ml 48824-1312 USA fax: (517) 353-1926; e-mail: 23274fwe@msu.edu, , , , , , US.
authors.forename: Frank W
authors.initials: FW
authors.lastname: Ewers
authors.affiliation: INRA, Unite d'Ecophysiologie Forestiere, F-54280 Champenoux, France, , , , , , FR.
authors.forename: Herve
authors.initials: H
authors.lastname: Cochard
authors.affiliation: Aiken Forestry Science Laboratory, US Forest Service, PO Box 968, Burlington, VT 05402, USA and Smithsonian Tropical Research Institute, PO Box 2072, Balboa, Republic of Panama, , , , , , PA.
authors.forename: Melvin T
authors.initials: MT
authors.lastname: Tyree
keywords: Key words Lianas ;  Barro Colorado Island;  Root pressure ;  Vines ;  Xylem water potential 