The amount of F-actin is reduced within the apical region of <i>fh3</i>, <i>fh5</i>, and <i>fh3 fh5</i> pollen tubes.

(A) Micrographs of pollen tubes stained with Alexa-488 phalloidin. For each genotype, the upper panel shows the Z-projection images. The reslices of transverse sections of the boxed region are shown (their distance from the tip is indicated on the image). The longitudinal sections of the stained pollen tubes are also presented and the dashed blue lines indicate the base of the subapical region that was used to quantify the fluorescence intensity of the actin filaments. The bottom panels show enlarged images of the actin filament staining in the boxed region of the top panel. These images were projected from the 5 optical sections at the cortex (shown in the middle panels). White arrows indicate some short and fragmented actin bundles within the apical region of fh3-1 and fh3-1 fh5-2 pollen tubes. Bar = 10 μm. (B) Plot of the fluorescence intensity of actin filaments from the tip to the base of pollen tube. The dashed blue lines indicated the base of the subapical regions as shown in (A). (C) Quantification of the relative fluorescence intensity of actin filaments within the apical and subapical region (from the tip to the dashed blue line) of pollen tubes. Data are presented as mean ± SE, statistical comparisons were performed using ANOVA Post-Tukey, ** P D) Quantification of the fluorescence intensity of actin filaments within the shank region of pollen tubes. Data were presented as mean ± SE, statistical comparisons were performed using ANOVA Post-Tukey, ** P E) The 2D distribution of fluorescence pixel intensity of actin filaments within the apical region was generated using ImageJ software with a 3D interactive surface plot function. (F) Plot of the average angles formed between actin filaments and the pollen tube growth axis within the apical region of pollen tubes. The left panel is a schematic showing the measurement of the angles formed between actin filaments and the growth axis of the pollen tube. θ1 and θ2 represent the angles measured within apical region and shank region of the pollen tube, respectively. The right panel is the plot of average angles. Data represent mean ± SE. More than 200 apical actin filaments or bundles were measured from 10 pollen tubes for each genotype. Statistical comparisons were performed using ANOVA Post-Tukey, *P G) Plot of the average angles (θ2) formed between actin filaments and the pollen tube growth axis within the shank region of pollen tubes. Data represent mean ± SE. More than 150 actin filaments were measured from 10 pollen tubes for each genotype. Statistical comparisons were performed using ANOVA Post-Tukey, *P < 0.05. **P < 0.01.