Improvement to the air-injection technique to estimate xylem vulnerability to cavitation |
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Authors: | Mustapha Ennajeh Mourad Nouiri Habib Khemira Herv?? Cochard |
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Institution: | (1) D?partment des Sciences de la Vie, Facult? des Sciences de Gab?s, Universit? de Gab?s, Cit? Erriadh-Zrig, 6072 Gab?s, Tunisia;(2) Laboratoire de Physique des Mat?riaux et des Nanomat?riaux appliqu?e a l’Environnement, Facult? des Sciences de Gab?s, Universit? de Gab?s, Cit? Erriadh-Zrig, 6072 Gab?s, Tunisia;(3) INRA, UMR 547 PIAF, 63100 Clermont-Ferrand Cedex 01, France;(4) Universit? Blaise Pascal, UMR 547 PIAF, 63177 Aubi?re Cedex, France; |
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Abstract: | Several techniques have been developed to quantify the degree of embolism of the xylem using hydraulic conductance. Although
there have been several improvements to these techniques, their reliability is still questionable and many technical pitfalls
persist. We are proposing here a manometric approach to improve the accuracy of xylem cavitation measurement by the original
air-injection technique which uses twigs exposed to pressurized air to cause cavitation. The measured parameter is air bubble
production (P
b) caused by xylem cavitation in birch (Betula pendula Roth) twigs from which the percent increase in bubble production is calculated to quantify xylem cavitation. Data produced
by three different methods (bench-drying, air-injection, and manometric approach) are compared. Xylem vulnerability curves
(VCs) constructed by the reference and reliable bench-drying technique and the manometric approach show similar sigmoid “S”
shape, but a small anomaly appeared in the VC constructed by the original air-injection technique. The xylem pressure inducing
50% of embolism (P
50) was the same with the three techniques. Furthermore, there was a strong positive correlation between the estimators of xylem
cavitation measured by the three different methods. For its reliability, precision and ease we recommend the manometric technique
as an improved version of the original hydraulic air-injection method. |
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