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Xylem Flow and its Driving Forces in a Tropical Liana: Concomitant Flow‐Sensitive NMR Imaging and Pressure Probe Measurements
Author(s) -
Wistuba N.,
Reich R.,
Wagner H.J.,
Zhu J. J.,
Schneider H.,
Bentrup F.W.,
Haase A.,
Zimmermann U.
Publication year - 2000
Publication title -
plant biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.871
H-Index - 87
eISSN - 1438-8677
pISSN - 1435-8603
DOI - 10.1055/s-2000-16644
Subject(s) - xylem , turgor pressure , liana , osmotic pressure , biology , apex (geometry) , transpiration , pressure gradient , transpiration stream , botany , water flow , tension (geology) , biophysics , flow (mathematics) , mechanics , materials science , soil science , environmental science , physics , photosynthesis , composite material , ultimate tensile strength
Flow‐sensitive NMR imaging and pressure probe techniques were used for measuring xylem water flow and its driving forces (i.e., xylem pressure as well as cell turgor and osmotic pressure gradients) in a tropical liana, Epipremnum aureum. Selection of tall specimens allowed continuous and simultaneous measurements of all parameters at various distances from the root under diurnally changing environmental conditions. Well hydrated plants exhibited exactly linearly correlated dynamic changes in xylem tension and flow velocity. Concomitant multiple‐probe insertions along the plant shoot revealed xylem and turgor pressure gradients with changing magnitudes due to environmental changes and plant orientation (upright, apex‐down, or horizontal). The data suggest that in upright and ‐ to a lesser extent ‐ in horizontal plants the transpirational water loss by the cells towards the apex during the day is not fully compensated by water uptake through the night. Thus, longitudinal cellular osmotic pressure gradients exist. Due to the tight hydraulic coupling of the xylem and the tissue cells these gradients represent (besides the transpiration‐induced tension in the xylem) an additional tension component for anti‐gravitational water movement from the roots through the vessels to the apex.