Pollen Tube Growth and the Intracellular Cytosolic Calcium Gradient Oscillate in Phase while Extracellular Calcium Influx Is Delayed

Ratio images of cytosolic ${\rm Ca}^{2+}\ ({\rm Ca}^{2+}{}_{{\rm i}})$ in growing, fura-2-dextran-loaded Lilium longiflorum pollen tubes taken at 3- to 5-sec intervals showed that the tip-focused [ Ca2+] i gradient oscillates with the same period as growth. Similarly, measurement of the extracellula...

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Bibliographic Details
Published in:The Plant cell 1997-11, Vol.9 (11), p.1999-2010
Main Authors: Holdaway-Clarke, Terena L., Feijó, José A., Hackett, Grant R., Kunkel, Joseph G., Hepler, Peter K.
Format: Article
Language:English
Subjects:
Calcium
Cell growth
Cell membranes
Cell walls
Datasets
Electrodes
Oscillation
Plant cells
Plants
Pollen tubes
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Summary:Ratio images of cytosolic ${\rm Ca}^{2+}\ ({\rm Ca}^{2+}{}_{{\rm i}})$ in growing, fura-2-dextran-loaded Lilium longiflorum pollen tubes taken at 3- to 5-sec intervals showed that the tip-focused [ Ca2+] i gradient oscillates with the same period as growth. Similarly, measurement of the extracellular inward current, using a noninvasive ion-selective vibrating probe, indicated that the tip-directed extracellular ${\rm Ca}^{2+}\ ({\rm Ca}^{2+}{}_{{\rm o}})$ current also oscillates with the same period as growth. Cross-correlation analysis revealed that whereas the [ Ca2+] i gradient oscillates in phase with growth, the influx of ${\rm Ca}^{2+}{}_{{\rm o}}$ lags by ∼11 sec. Ion influx thus appears to follow growth, with the effect that the rate of growth at a given point determines the magnitude of the ion influx ∼11 sec later. To explain the phase delay in the extracellular inward current, there must be a storage of Ca2+ for which we consider two possibilities: either the inward current represents the refilling of intracellular stores (capacitative calcium entry), or it represents the binding of the ion within the cell wall domain.
ISSN:1040-4651
1532-298X
DOI:10.1105/tpc.9.11.1999