Figure 4.

Treatment with Spm dramatically modifies the pH gradient at the pear pollen tube apex. (A) In controls, pollen tubes have a tip-oriented pH gradient with an acidic region located at the tube apex. The pH acid region disappears shortly after 5–10 μm from the apex and only a weak background signal can be observed. (B) The data is confirmed by the relative measurement of the fluorescence intensity that is representative of three independent experiments. (C) At the balloon stage of Spm-treated pollen tubes, the pH gradient changes and the highest H⁺ concentration is redistributed throughout the surface of the swelling apex. (D) At the shovel stage, H⁺ concentration is approximately homogeneous throughout the new enlarged pollen tube. No H⁺ accumulation was observed at the apex of the new pollen tube. Bar = 10 μm.