The nonmotile sperm cells of higher plants are transported directly to the egg cells, at the base of the style, through a tube which germinates from the male gametophyte. The tube must penetrate the style and grow up to a foot long in order to reach the eggs. The tubes elongate by adding new cell wall and cell membrane components through site-directed vesicle fusion. Recently it has been found that this growth in pollen tubes is not steady but pulsatile. The growth rate of lily pollen tubes oscillate between 0.1 and 0.4 ?m/sec with an average period of 40 seconds. We have shown that a tip-high gradient of [Ca2+] I oscillates in phase with the growth pulse, rising during peak growth rates, and that a tip-high gradient of [H+]i oscillates with growth but lags the growth pulse by 7.5 seconds. Using the current vibrating probe we found an influx of current which lagged the growth pulses also by 7.5 seconds. By decreasing the extracellular K+ concentration we were able to dampen the amplitu de of the current influx. This suggests that K+ is a component of the current influx. The timing of these two pulsing events suggests simultaneous transport of K+ and H+ occuring just as the growth rate is decreasing. The lag in the K+ and H+ influx appears to be slowing down if not stopping pollen tube growth. Our work at the Biocurrents Research Center involves using the self-referencing probes to measure the influx of H+ and K+ and correlate their changes with tube growth. Our hypothesis suggests that a 1:1 ratio of H+ and K+ influx lag the growth pulses by about 7.5 seconds. While Ca2+, H+, and K+ are oscillating during pulsatile growth, we are also trying to determine the mechanism which generates pulsatile growth. One possibility suggested was that, metabolism is controlling the pulsatile growth. An older literature involving yeast, discusses oscillations in metabolic intermediates with similar periods as the pollen tube tip growth. Therefore, we propose to use the O2 probe to scan our rapidly growing pollen tubes for oxygen consumption. Oxygen consumption should be a direct determinant of theaerobic energy production needed for tube growth.