Studies on mechano-perception in the Characeae: transduction of pressure signals into electrical signals.
Mechano-perception by Chara cells was studied with an emphasis on the role of the nodal complex in transducing pressure signals into electrical signals. Three types of experimental material were used: (1) tandem internodal cells connected by a single layer of nodal cells; (2) single internodal cells, from which either apical or basal nodes were removed by ligation and cutting; (3) single internodes from which both nodes had been removed. Exposure to a hypertonic solution (sorbitol or sucrose) induced a depolarization at the node in 1 and 2. Depolarization did not occur at the ligated end of the cell in 2, or at all in 3. Addition of K+ increased the magnitude of the response, whilst it was significantly decreased by the divalent cations, Ca2+ and Mg2+. Electrical resistance decreased at the node during the depolarization, showing that a passive diffusion potential was responsible. I suggest that the change in the trans-nodal hydraulic pressure difference mechanically stretches the plasma membrane, and this induces the electrical depolarization.
Shimmen
Teruo
T
Department of Life Science, Graduate School of Science, Himeji Institute of Technology, Harima Science Park City, Hyogo, 678-1297 Japan. shimmen@sci.himeji-tech.ac.jp
D044522:Characeae / Q000502:physiology*; D008839:Microelectrodes; D011312:Pressure; D015398:Signal Transduction; D013395:Sucrose / Q000494:pharmacology
D013395:Sucrose