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Comparison of four methods for measuring osmotic potential of tree leaves


  • Edited by V. Hurry



Osmotic potential (π) of tree leaves is usually determined by pressure-volume (PV) analysis, which is too time consuming for large-scale assessments such as ecological surveys and genetic screening. We investigated methods for rapid measurement of π in sclerophyllous species. The osmotic potential of expressed sap (ES), freeze-thaw leaf discs and hot water extracts – measured using a variety of techniques – were compared with PV analysis using sclerophyllous species; Eucalyptus globulus Labill., E. camaldulensis Dehnh., E. cladocalyx F. Muell. and non-sclerophyllous species; Populus nigra L and Alnus jorullensis H.B.K. All methods were sensitive to changes in π and produced results that were unequal but well correlated (r2 0.82–0.90). The proportion of leaf water extracted in ES was reduced by low water content and sclerophylly without affecting method accuracy. PV analysis provided a poor correction for apoplastic dilution of ES. Results of ES osmometry and PV analysis were comparable, and osmometry of ES is proposed as a suitable method for large-scale investigations of leaf π.