Data Entry: Please note that the research database will be replaced by UNIverse by the end of October 2023. Please enter your data into the system https://universe-intern.unibas.ch. Thanks
Water relations of climbing ivy in a temperate forest
Journal
Planta
Volume
233
Number
6
Pages / Article-Number
1087-96
Keywords
Global warming, Granier method, Hedera, Lianas, Sap flow, Stomatal conductance, Leaf water potential
Abstract
Ivy (Hedera helix) is the most important liana in temperate European forests. We studied water relations of adult ivy in a natural, 35 m tall mixed deciduous forest in Switzerland using a construction crane to access the canopy. Predawn leaf water potential at the top of climbing ivy ranged from -0.4 to -0.6 MPa, daily minima ranged from -1.3 to -1.7 MPa. Leaf water potentials as well as relative sap flow were held surprisingly constant throughout different weather conditions, suggesting a tendency to isohydric behaviour. Maximum stomatal conductance was 200 mmol m(-2) s(-1). The use of a potometer experiment allowed us to measure absolute transpiration rates integrated over a whole plant of 0.23 mmol m(-2) s(-1). Nightly sap flow of ivy during warm, dry nights accounted for up to 20% of the seasonal maximum. Maximum sap flow rates were reached at ca. 0.5 kPa vpd. On the other hand, the host trees showed a less conservative stomatal regulation, maximum sap flow rates were reached at vpd values of ca. 1 kPa. Sap flow rates of ivy decreased by ca. 20% in spring after bud break of trees, suggesting that ivy profits strongly from warm sunny days in early spring before budbreak of the host trees and from mild winter days. This species may benefit from rising winter temperatures in Europe and thus become a stronger competitor against its host trees.
