Fig. 1 Upper and side view of a double-chamber osmometer made of plexiglass for measuring transroot water movement. An isolated root (r) is embedded in the groove of the partition wall with lanolin wax so that the apical part (about 40 mm) is in open pool A and the basal part (about 10 mm) in closed chamber B. A sealing block (s) is fitted on the partition wall with lanolin to make the junction between the two compartments watertight. Pool A and chamber B are filled with APW. After filling chamber B with APW and introducing the air bubble (b) into the capillary (C), the hole (h) is closed with a plastic tap (t). Transroot osmosis is induced by replacing APW in A with APW containing sorbitol. The volume of water transported from B to A is indicated by the distance of movement of the air bubble (b). Onion Root Water Transport Sensitive to Water Channel andK+ ChannelInhibitors Plant Cell Physiol. 2001;42(1):28-36. doi:10.1093/pcp/pce004 Plant Cell Physiol |

Fig. 2 Turgor balance for measuring deformation of a root Fig. 2 Turgor balance for measuring deformation of a root. The balance is supported by two needles which act as fulcra (f). It has two arms, a plexiglass plate (A) and a brass screw (B). A glass capillary (g) is attached to the longer arm (A). A fine tip of the capillary is observed with a traveling microscope and its movement is observed with the eyepiece micrometer (M). A detached root or a root segment (r) is placed in the plexiglass chamber (C) containing APW and is pressed through the plexiglass plate (p) of the balance. The load on the root can be controlled by changing the length of the chain (ch) with a rolling wheel (W). Onion Root Water Transport Sensitive to Water Channel andK+ ChannelInhibitors Plant Cell Physiol. 2001;42(1):28-36. doi:10.1093/pcp/pce004 Plant Cell Physiol |

Fig. 3 (a) Diagram of apparatus for measuring the electric potential difference (P.D.) between the apical and basal part of the isolated onion root partitioned in pools A and B across the partition wall. The P.D. was amplified with an amplifier and recorded with a pen-writing recorder (REC). (b) Diagram for measuring the membrane potential (E_m) of root cortex cells. A root segment of about 15 mm long was fixed at two loci between the fixed plexiglass plates p1 and p3 and the movable plates p2 and p4 with vaseline at the bottom. µ, glass microelectrode; ref, reference electrode connected to the earth. Onion Root Water Transport Sensitive to Water Channel andK+ ChannelInhibitors Plant Cell Physiol. 2001;42(1):28-36. doi:10.1093/pcp/pce004 Plant Cell Physiol |

Fig. 4 Repetition of transroot osmosis induced by 0 Fig. 4 Repetition of transroot osmosis induced by 0.2 M sorbitol in an onion root without infiltration. The numbers next to the curves indicate the order of repeated osmosis. Onion Root Water Transport Sensitive to Water Channel andK+ ChannelInhibitors Plant Cell Physiol. 2001;42(1):28-36. doi:10.1093/pcp/pce004 Plant Cell Physiol |

Fig. 5 Transroot osmosis induced by 0 Fig. 5 Transroot osmosis induced by 0.2 M sorbitol before (25°C, closed squares) and after chilling treatment (5°C, closed circles) in an infiltrated onion root. The duration of chilling treatment was 26.5 h. All measurements were done at 25°C. Onion Root Water Transport Sensitive to Water Channel andK+ ChannelInhibitors Plant Cell Physiol. 2001;42(1):28-36. doi:10.1093/pcp/pce004 Plant Cell Physiol |

Fig. 6 Deformation of an onion root during transroot osmosis induced by 0.2 M sorbitol. The root with an apical length of 27 mm was loaded with a weight at a locus 20 mm from the apical tip. First, a non-infiltrated root was subjected to transroot osmosis (1). The second osmosis (2) was conducted after infiltration of the same root. The same root was then stored in APW at 5°C for 22 h and the third osmosis was done at 22°C (3). Onion Root Water Transport Sensitive to Water Channel andK+ ChannelInhibitors Plant Cell Physiol. 2001;42(1):28-36. doi:10.1093/pcp/pce004 Plant Cell Physiol |

Fig. 7 Inhibition of non-osmotic water transport by C₉ in an onion root. First the apical and basal parts of the root were bathed in APW (open circles). Next, APW in the apical part was substituted with APW containing 1 mM C₉ (close circles). Onion Root Water Transport Sensitive to Water Channel andK+ ChannelInhibitors Plant Cell Physiol. 2001;42(1):28-36. doi:10.1093/pcp/pce004 Plant Cell Physiol |

Fig. 8 J_nos in relation to J_os. The root was infiltrated before measurement. The numbers next to the curve indicate the order of measurements. At all points, J_nos was measured, and then transroot osmosis was induced by 0.1 M sorbitol to obtain J_os. Measurements at point 4 were done after treatment of the root with 1 mM C₉ for 30 min. Onion Root Water Transport Sensitive to Water Channel andK+ ChannelInhibitors Plant Cell Physiol. 2001;42(1):28-36. doi:10.1093/pcp/pce004 Plant Cell Physiol |

Fig. 9 Effect of C₉ on the change in the potential difference (P.D.) between the apical and basal parts of onion roots in relation to the K⁺ concentration of the external medium of the apical part. Although the P.D. at 0.1 mM K⁺ (APW) was not zero (minus several mV), it was set to zero for the sake of convenience. Open circles: control roots. Closed circles: roots treated with 1 mM C₉ for about 90 min. To change [K⁺]_o, KCl was added to APW. The solution of the basal part was APW to which sorbitol was added to keep the osmolarity of the solution equal to that of the medium in A. Bars show ± SD. The number of roots used was six for the control and seven for the C₉. Onion Root Water Transport Sensitive to Water Channel andK+ ChannelInhibitors Plant Cell Physiol. 2001;42(1):28-36. doi:10.1093/pcp/pce004 Plant Cell Physiol |

Fig. 10 Membrane potential of cortical cells of onion roots in relation to the concentration of K⁺. Open circles: control roots. Closed circles: roots treated with 1 mM C₉ for about 90 min. To adjust [K⁺]_o KCl was added to APW. Bars show ± SD. The number of roots used was eight for the control and 12 for C₉. Onion Root Water Transport Sensitive to Water Channel andK+ ChannelInhibitors Plant Cell Physiol. 2001;42(1):28-36. doi:10.1093/pcp/pce004 Plant Cell Physiol |

Fig. 11 Effect of HgCl₂ on the change in the potential difference (P.D.) between the apical and basal parts of onion roots in response to [K⁺]_o of the apical part. Open circles: control roots. Closed circles: roots treated with 100 µM HgCl₂ for about 35 min. Three roots were used for the control and five for the HgCl₂ treatment. Bars indicate ± SD. Onion Root Water Transport Sensitive to Water Channel andK+ ChannelInhibitors Plant Cell Physiol. 2001;42(1):28-36. doi:10.1093/pcp/pce004 Plant Cell Physiol |