Pulsatile influxes of H+, K+ and Ca2+ lag growth pulses of Lilium longiflorum pollen tubes.
Fluxes of H+, K+ and Ca2+ were measured with self-referencing ion-selective probes, near the plasma membrane of growing Lilium longiflorum pollen tubes. Measurements from three regions around short, steady-growing tubes showed small, steady influx of H+ over the distal 40 microm and a region of the tube within 50-100 microm of the grain with larger magnitude efflux from the grain. K+ fluxes were immeasurable in short tubes. Measurements of longer tubes that were growing in a pulsatile manner revealed a pulsatile influx of both H+ and K+ at the growing tip. The average fluxes at the cell surface during the peaks of the H+ and K+ pulses were 489+/-81 and 688+/-144 pmol cm-2 second-1, respectively. Growth was measured by tracking the pollen tips with a computer vision system that achieved a spatial resolution of approximately 1/10 pixel. The high spatial resolution enabled the detection of growth, and thus the changes in growth rates, with a temporal sampling rate of 1 frame/second. These data show that the H+ and K+ pulses have a phase lag of 103+/-9 and 100+/-11 degrees, respectively, with respect to the growth pulses. Calcium fluxes were also measured in growing tubes. During steady growth, the calcium influx was relatively steady. When pulsatile growth began, the basal Ca2+ influx decreased and a pulsatile component appeared, superimposed on the reduced basal Ca2+ flux. The peaks of the Ca2+ pulses at the cell surface averaged 38.4+/-2.5 pmol cm-2 second-1. Longer tubes had large pulsatile Ca2+ fluxes with smaller baseline fluxes. The Ca2+ influx pulses had a phase lag of 123+/-9 degrees with respect to the growth pulses.
Messerli
M A
MA
Department of Biological Sciences, West Lafayette, IN 47907-1392, USA.
Danuser
G
G
Robinson
K R
KR
D002118:Calcium / Q000378:metabolism*; D002455:Cell Division; D004594:Electrophysiology; D006859:Hydrogen / Q000378:metabolism*; D017136:Ion Transport; D019668:Liliaceae / Q000378:metabolism*; D018715:Microscopy, Video; D011058:Pollen / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism*; D012984:Software; D013997:Time Factors
D006859:Hydrogen; D011188:Potassium; D002118:Calcium