IN-SITU PLANT WATER-BALANCE STUDIES USING A PORTABLE NMR SPECTROMETER

A portable H-1 NMR spectrometer has been applied to whole plants in si tu, i.e. in climate rooms and in a greenhouse, to study plant water re lations under these conditions. The spectrometer consists of a 30 kg p ermanent magnet system of 0.235 T, modified Bruker Minispec electronic s, and a standard XT pc for spectrometer control. Unattended, the syst em automatically measures the xylem sap stream and tissue water conten t in a well-defined section of the plant stem. Because of the small si ze of the magnet these measurements can be made at different positions on the plant stem or on different plants in succession. Magnetic fiel d drift due to the varying climates that occur in greenhouses was corr ected by field locking. Results are presented for a single plant in a climate room, demonstrating a method for the study of plant water hydr aulics. In addition, a single plant in a greenhouse crop was measured, and the NMR results were compared with the water uptake and transpira tion rates under (natural) variation of light intensity and relative h umidity, demonstrating the reliability of the portable NMR under reali stic greenhouse conditions. Finally, the application for the measureme nt of the root water uptake efficiency is demonstrated for a number of grafted cucumber plants under constant climatic conditions in a phyto tron.