Ca2+ regulates reactive oxygen species production and pH during mechanosensing in Arabidopsis roots.

Mechanical stimulation of plants triggers a cytoplasmic Ca(2+) increase that is thought to link the touch stimulus to appropriate growth responses. We found that in roots of Arabidopsis thaliana, external and endogenously generated mechanical forces consistently trigger rapid and transient increases in cytosolic Ca(2+) and that the signatures of these Ca(2+) transients are stimulus specific. Mechanical stimulation likewise elicited an apoplastic alkalinization and cytoplasmic acidification as well as apoplastic reactive oxygen species (ROS) production.

Seasonal changes of plasma membrane H(+)-ATPase and endogenous ion current during cambial growth in poplar plants.

The plasma membrane H(+)-ATPase (PM H(+)-ATPase), potassium ions, and endogenous ion currents might play a fundamental role in the physiology of cambial growth. Seasonal changes of these parameters were studied in twigs of Populus nigra and Populus trichocarpa. Monoclonal and polyclonal antibodies against the PM H(+)-ATPase, x-ray analysis for K(+) localization and a vibrating electrode for measurement of endogenous ion currents were used as probes.

Ion fluxes, auxin and the induction of elongation growth in Nicotiana tabacum cells.

Immobilized cultured tobacco cells become polarized upon the addition of naphthalene-1-acetic acid and start to elongate from an initial spherical shape. The question as to how a diffuse-growing cell forms a polar axis is addressed here with approaches successfully applied to the study of tip growth. With two kinds of vibrating probes the electric current flow and proton fluxes were mapped around such elongating cells.

Bioelectricity, gravity and plants.

This brief review summarizes gravity-induced changes in bioelectric parameters and evaluates their contribution to our understanding of the sensing of gravity, and the transduction and transmission of the gravity stimulus in plants. During the last few decades, information has accumulated demonstrating gravity-induced changes in surface potentials, membrane voltages, endogenous electric currents and ion fluxes. These changes point to the plasma membrane as the site of perception and transduction of the gravity signal.

Wound-Induced Changes of Membrane Voltage, Endogenous Currents, and Ion Fluxes in Primary Roots of Maize.

The effects of mechanical wounding on membrane voltage, endogenous ion currents, and ion fluxes were investigated in primary roots of maize (Zea mays) using intracellular microelectrodes, a vibrating probe, and ion-selective electrodes. After a wedge-shaped wound was cut into the proximal elongation zone of the roots, a large inward current of approximately 60 [mu]A cm-2 was measured, together with a change in the current pattern along the root. The changes of the endogenous ion current were accompanied by depolarization of the membrane voltage of cortex cells up to 5 mm from the wound.