Comparison of the measurements of leaf water potential between a hydraulic press and a pressure chamber in six Sahelian woody species

Abstract

The aim of this methodological study was to quantify differences between water potential measured with a pressure chamber (PC) and with a hydraulic press (HP) in six north Sahelian dominant species of the woody strata across the range of their local environmental conditions in the Malian Gourma. Mean annual rainfall is 372 mm, falling from June to September, followed by 8–10 months of dry season. The daily course of Leaf Water Potential (LWP) was monitored in 2–6 m tall healthy individuals. Water potential measured with the two instruments were statistically comparable (R² > 40%) except in A. senegal. However, the HP under-estimated LWP and revealed smaller ranges of water potential than the PC. In the Sahelian shrubs studied here, for the precise measurement of a water potential gradient in the soil–plant-atmosphere continuum and for inter-specific comparisons, the PC is more appropriate than the HP. However, the HP may be useful for intra-species comparison in large sampled fields, since calibrations will be checked across a wider range of dates and a large number of sites.