Fig. 3: Reduced pollen tube growth in aha6 double and triple mutants is associated with reduced extracellular ion fluxes and intracellular pH gradients.

a Representative WT pollen tube summarizing H⁺ fluxes measured at the surface (arrows) and cytosolic pH gradient (false color). Arrow size is scaled with the flux intensity shown on the bottom bar, while direction denotes influx or efflux. b Extracellular H⁺ fluxes at the pollen tube tip. Violin plots show the probability density with color-filled curves obtained from individual observations (open gray circles), with boxplots (thick black lines and outliers as black dots) overlaid with the mean and standard error (red circle and lines). c Extracellular H⁺ fluxes throughout the pollen tube sampled every 5 µm, averaged and interpolated with a local polynomial fit (loess) with n > 10 for all genotypes. Negative values indicate influx and positive values efflux. d Extracellular anion efflux at the tip. e Cytosolic pH throughout the tube averaged with loess for each genotype (n > 16), obtained by fluorescence imaging of a calibrated pH probe (pHluorin). Media pH indicated by dashed line. f Gradient steepness estimated by the fold change in cytoplasmic pH between the tip and shank (subcellular regions defined as in Fig. 4). g Average growth rate correlates with pH ratio between the tip and shank (linear fit in blue with standard deviation shaded), while its does not correlate with tip pH alone (Fig. S9). Where applicable, asterisks indicate a significant difference (p < 0.01) compared to the control (WT); one-way ANOVA followed by the post-hoc Dunnett test.