Plant hydraulic conductance measured by the high pressure flow meter in crop plants

A new high pressure flow meter (HPFM) method for measuring plant hydraulic conductances (K) was investigated to examine whether its results are compar able to those from a conventional evaporative flux (EF) method in crops. Hy draulic conductance (K) was measured by the two methods under quasi-steady- state conditions in six crops grown in pots: soybean (Glycine max L. Merr. cv. Tsurunoko daizu), sunflower (Helianthus annuus L. cv. Russian mammoth), kidney bean (Phaseolus vulgaris L. cv. Tsurunashi morocco), tomato (Lycope rsicon esculentum Mill. cv. Sekai-ichi), green pepper (Capsicum annuum L, c v, shishitou), and eggplant (Solanum melongena L, cv, Seiguro chunaga nasu) . There was a 1:1 agreement between K values measured by the two methods fo r K values of whole plant, root and stem, and leaf under quasi-steady-state conditions. Leaf water potential (Psi(leaf)) and evaporative flux density (E) in sunflower was curvilinear, indicating whole plant K estimated by the EF method increased with increase of E, Predicted Psi(leaf) (=E divided by whole plant K measured by the HPFM method) agreed with measured Psi(leaf). Diurnal changes were also found in K measured by the HPFM confirming that K changed in response to temperature and E. The HPFM revealed that variable conductance was located in all organs: roots, stems, petioles, and leaves. These observations indicated that the HPFM is valid for crops as well as f or trees (as previously established by Tsuda and Tyree) and has advantages over the EF method because of the speed and ease of the HPFM method.