ibclogo XVI International Botanical Congess


Abstract Number: 5371
Session = 16.14.1


WATER UPTAKE AND TRANSPORT


E. Steudle, Universitaet Bayreuth, Germany


A composite transport model explains the variability of root hydraulic conductivity (Lpr) and its responses to demands for water from the shoot and environmental factors. During water stress, root Lpr is optimized by a 'coarse' and 'fine' regulation. Coarse regulation of Lpr is physical in nature and depends on root anatomy (apoplastic barriers in the exo- and endodermis). Fine regulation results from the activity of aquaporins in root cell membranes. Direct measurement of tensions in the xylem of transpiring maize plants (pressure probe) agreed with the cohesion-tension theory. Previous conclusions drawn from such measurements were premature because the technique was not critically assessed for its limitations. Xylem pressures of down to -1 MPa rapidly responded to transpiration and pressures applied to the root. Xylem pressures measured directly agreed with those obtained with the Scholander bomb.


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