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Effects of the hydraulic coupling between xylem and phloem on diurnal phloem diameter variation
Author(s) -
SEVANTO SANNA,
HÖLTTÄ TEEMU,
HOLBROOK N. MICHELE
Publication year - 2011
Publication title -
plant, cell and environment
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.646
H-Index - 200
eISSN - 1365-3040
pISSN - 0140-7791
DOI - 10.1111/j.1365-3040.2011.02275.x
Subject(s) - phloem , xylem , hydraulic conductivity , fluid coupling , conductance , diurnal temperature variation , botany , biophysics , biology , mechanics , physics , ecology , atmospheric sciences , soil water , condensed matter physics
Measurements of diurnal diameter variations of the xylem and phloem are a promising tool for studying plant hydraulics and xylem–phloem interactions in field conditions. However, both the theoretical framework and the experimental verification needed to interpret phloem diameter data are incomplete. In this study, we analytically evaluate the effects of changing the radial conductance between the xylem and the phloem on phloem diameter variations and test the theory using simple manipulation experiments. Our results show that phloem diameter variations are mainly caused by changes in the radial flow rate of water between the xylem and the phloem. Reducing the hydraulic conductance between these tissues decreases the amplitude of phloem diameter variation and increases the time lag between xylem and phloem diameter variation in a predictable manner. Variation in the amplitude and timing of diameter variations that cannot be explained by changes in the hydraulic conductance, could be related to changes in the osmotic concentration in the phloem.