Journal ArticleDOI
Auxin causes oscillations of cytosolic free calcium and pH inZea mays coleoptiles.
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TLDR
It is concluded that this onset of regulatory processes through the phytohormone IAA is indicative of calcium and protons mediating early auxin action in maize coleoptiles and the double-barrelled ion-sensitive microelectrode is an invaluable tool for investigating in-vivo hormone action in plant tissues.Abstract:
In epidermal cells of maize (Zea mays L.) coleoptiles, cytosolic pH (pHc), cytosolic free calcium, membrane potential and changes thereof were monitored continuously and simultaneously (pHc/,ψm, Ca2+/ψm) using double-barrelled ion-sensitive microelectrodes. In the resting cells the cytosolic pH was 7.3–7.5 and the concentration of free calcium was 119±24 nM. One-micromolar indole-3-acetic acid (IAA), added to the external medium at pH 6.0 triggered oscillations inψm, pHc and free calcium with a period of 20 to 30 min. Acidification of the cytosolic pH increased the cytosolic free calcium. Theψm oscillations are attributed to changes in activity of the H+-extrusion pump at the plasmalemma, triggered off by ΔpH and controlled by pH regulation (pH oscillation). The origin of the pHc and Ca2+ changes remains unclear, but is possibly caused by auxin-receptor-induced lipid breakdown and subsequent second-messenger formation. It is suggested that the observed cytosolic pH and Ca2+ changes are intrinsically interrelated, and it is concluded that this onset of regulatory processes through the phytohormone IAA is indicative of calcium and protons mediating early auxin action in maize coleoptiles. It is further concluded that the double-barrelled ion-sensitive microelectrode is an invaluable tool for investigating in-vivo hormone action in plant tissues.read more
Citations
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Calcium in Plants
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References
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The Polar Transport of Auxin
TL;DR: In this paper, anion permeability-simple diffusion usion or carrier-mediated diff usion was used to detect the path of auxin transport in a micro-autoradiography.
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Experiments and hypothesis concerning the primary action of auxin in elongation growth
TL;DR: The findings suggest that auxin induces a proton accumulation in a cell wall compartment and, as a consequence, enzymatic cell wall softening, which may be the last step in the process of cell elongation.
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Neutral carrier ion-selective microelectrodes for measurement of intracellular free calcium
R.Y. Tsien,T.J. Rink +1 more
TL;DR: Electrodes showed a Nernstian response to [Ca2+] down to 1 micro M free concentration in 0.1 M KCl, and usually a useful response to below 100 nM Ca2+.