title: Gravity induced changes in intracellular potentials in statocytes of cress roots.
abstract: Two glass microelectrodes were inserted from opposite sides of the root cap into statocytes of Lepidium sativum L. immersed in medium with or without cytochalasin D (CD). Intracellular potentials (Eis) of statocytes were measured with reference to an earthed electrode in the bathing solution. In the absence of CD, Ei values were -160 +/- 2 mV (n = 52) in vertical roots. During the recording of Eis, the roots were tilted from the vertical by 45 degrees so that in a tilted root one electrode was on the upper side and the other on the lower side; after 5 min the roots were returned to the vertical. At approximately 64 s after tilting (lasting 5-15 s) there was a transient lowering of Ei (more negative) by an average of 4.7 mV on both the upper and lower sides (n = 52). In some cases, this decrease in Ei was preceded by a transitory increase. Returning the roots to the vertical resulted in a response similar to that obtained by tilting. In roots treated with CD at a concentration of 3 (microM for 1 h, the initial Ei was -145 +/- 2 mV (n = 43), and the lowering of Ei on position change (tilting or returning) was smaller (2.0 mV) in some statocytes (n = 50) and higher (8.1 mV) in others (n = 14) compared to control roots (without and with DMSO). A higher concentration (10 microM) of CD and longer treatment (2 h) further reduced the decrease in Ei (1.1 mV) on position change (n = 26). The observed effects of CD support the hypothesis that statoliths in statocytes are anchored by actin filaments to the plasma membrane and/or to the cortical endoplasmic reticulum. Movement of statoliths during the first step of graviperception may lead to stress changes in actin filaments, affecting the transmembrane potential and also the Ei.
authors.affiliation: Botanisches Institut, Universitat Bonn, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Sievers
authors.forename: C
authors.initials: C
authors.lastname: Sondag
authors.forename: K
authors.initials: K
authors.lastname: Trebacz
authors.forename: Z
authors.initials: Z
authors.lastname: Hejnowicz
mesh_terms: D019607:Brassicaceae / Q000187:drug effects / Q000502:physiology* / Q000648:ultrastructure*; D015638:Cytochalasin D / Q000494:pharmacology; D004594:Electrophysiology; D004721:Endoplasmic Reticulum / Q000502:physiology; D006112:Gravitation; D018522:Gravitropism / Q000502:physiology*; D018466:Gravity Sensing / Q000502:physiology*; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D008839:Microelectrodes; D018518:Plant Root Cap / Q000187:drug effects / Q000502:physiology* / Q000648:ultrastructure; D015398:Signal Transduction / Q000502:physiology
chemical_list: D015638:Cytochalasin D