A ¹H NMR study of water flow in Phaseolus vulgaris L. roots treated with nitrate or ammonium
2009
Schulze-Till, Thomas | Kaufmann, Ilja | Sattelmacher, Burkhard | Jakob, Peter | Haase, Axel | Guo, Shiwei | Zimmermann, Ulrich | Wegner, Lars H
The effect of N nutrition on root xylem (water) flow in Phaseolus vulgaris was studied by using the ¹H NMR flow imaging technique. Plants pre-cultivated on CaSO₄-solution were transferred to NMR-compatible split-root cuvettes filled with half-strength nitrate medium (2.5 mM). After 6 days full-strength (5 mM) nitrate medium was supplied to both compartments (NN treatment), or only to one compartment, whereas the other one was perfused with full-strength (5 mM) ammonium medium (NA treatment). Imaging was performed 7-8 days later. Root growth, xylem flow velocity and xylem pressure (measured with the xylem pressure probe) were largely unaffected by N nutrition. Under NA conditions, volume flow was significantly lower in ammonium- compared to nitrate-fed roots due to a reduced number of functional xylem elements. This was apparently not related to anatomical differences nor to an enhanced number of cavitated vessels in ammonium-fed roots. Vessels in these roots may become dysfunctional by clogging to prevent cavitation.
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