Pulsatile influxes of H+, K+ and Ca2+ tag 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 tube s. Measurements from three regions around short, steady-growing tubes showe d small, steady influx of H+ over the distal 40 mu m and a region of the tu be within 50-100 mu m of the grain with larger magnitude efflux from the gr ain. K+ fluxes were immeasurable in short tubes. Measurements of longer tub es that were growing in a pulsatile manner revealed a pulsatile influx of b oth H+ and K+ fat the growing tip. The average fluxes at the cell surface d uring the peaks of the H+ and K+ pulses were 489 +/- 81 and 688 +/- 144 pmo l cm(-2) second(-1), respectively. Growth was measured by tracking the poll en tips with a computer vision system that achieved a spatial resolution of approximately 1/10 pixel. The high spatial resolution enabled the detectio n 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 p hase 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, t he calcium influx was relatively steady. When pulsatile growth began, the b asal Ca2+ influx decreased and a pulsatile component appeared, superimposed on the reduced basal Ca2+ flux. The peaks of the Ca2+ pulses at the cell s urface 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.