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Behrens HM, Gradmann D, Sievers A. Membrane-potential responses following gravistimulation in roots of Lepidium sativum L. Planta. 1985;163(4):463-72doi: 10.1007/BF00392703.
Behrens, H. M., Gradmann, D., & Sievers, A. (1985). Membrane-potential responses following gravistimulation in roots of Lepidium sativum L. Planta, 163(4), 463-72. https://doi.org/10.1007/BF00392703
Behrens, H M, et al. "Membrane-potential responses following gravistimulation in roots of Lepidium sativum L." Planta vol. 163,4 (1985): 463-72. doi: https://doi.org/10.1007/BF00392703
Behrens HM, Gradmann D, Sievers A. Membrane-potential responses following gravistimulation in roots of Lepidium sativum L. Planta. 1985 Apr;163(4):463-72. doi: 10.1007/BF00392703. PMID: 24249445.
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Planta. 1985 Apr;163(4):463-72. doi: 10.1007/BF00392703.

Membrane-potential responses following gravistimulation in roots of Lepidium sativum L.

Planta

H M Behrens, D Gradmann, A Sievers

Affiliations

  1. Botanisches Institut der Universität, Venusbergweg 22, D-5300, Bonn.

PMID: 24249445 DOI: 10.1007/BF00392703

Abstract

Membrane potentials were measured in lateral statocytes of vertically and nonvertically growing roots of Lepidium sativum L. using conventional glass-microelectrode techniques. Statocytes in vertically growing roots showed a stable resting potential of-118±5.9 mV without spontaneous fluctuations. Upon tilting the root 45° from the vertical, an electrical asymmetry was observed. Statocytes on the physically lower side of the root depolarized by approx. 25 mV. This depolarization occurred following a latent period of 8 s reaching a minimum (approx.-93 mV) after 170 s. This depolarization is the earliest event in graviperception ever recorded. After this depolarization, the cell repolarized within 60 s to a potential approx. 10 mV more positive than the original resting potential. Statocytes on the upper flank showed a slow hyperpolarization (t 1/2h=half time for hyperpolarization=168 s) reaching a final, stable potential at a level 10 mV more negative. These effects of gravistimulation were statenchyma-specific, since cells in the cortex and rhizodermis showed no similar effects. The gravi-electrical responses were observed in 25% of all roots tested. Roots which showed no gravi-electrical response had a reduced elongation growth, lacked gravity-induced bending and lacked the typical structural polarity in punctured statocytes. This observed transition from a symmetrical pattern of resting potential in the statenchyma to an asymmetrical pattern following gravistimulation supports the results observed with external current measurements (Behrens et al., Plant Physiol. 70, 1079-1083, 1982) and extends these results to the cellular level and to considerably improved temporal resolution. The asymmetry in the gravi-electrical response extends the graviperception model of Sievers and Volkmann (Planta 102, 160-172, 1972) which comprises an asymmetrical sedimentation of the amyloplasts on the distal endoplasmic reticulum of statocytes. This generates an intraorgan signal which then must be transmitted to the growth zone.

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