Fig. 3.

Behavior of pollen tubes during passage through a microgap. (A) Effect of the ratio between pollen tube diameter and gap width on pollen tube behavior. Between ratios of 1.00 and 1.20, the pollen tubes deform the gap to pass almost without narrowing their diameter (green ▲). Below this ratio, the pollen tube diameter is reduced (light blue ◇) and frequently the tubes burst upon returning to the original diameter following gap passage (solid blue ◆). At a ratio of 1.33 and below, the tubes stall and cannot pass the gap (red ■). Each data point represents one interaction between a pollen tube and a microgap. (B) Change in growth rate during microgap passage. Upon encountering the gap at point S, the tube slows considerably but shows a constant growth rate despite the continuously narrowing gap. After exiting the narrowest region at point E, it starts growing faster but bursts soon after.