Study of auxin regulation of pollen tube growth through calcium channels in Pyrus pyrifolia

Although several studies have shown that auxin can promote pollen tube growth, the mechanism of regulation is unclear. Here, we report our studies showing that auxin increased pollen tube germination and pollen tube growth in Pyrus pyrifolia . This promotion markedly depended on extracellular pH. At pH 6.5 or 7.5, auxin effectively promoted pollen tube growth, but this effect disappeared at pH 4.5 or 5.5. This finding is consistent with the regulation of calcium channels by auxin. Auxin can increase the H + –ATPase activity of pollen tube. When sodium vanadate was used to inhibit H + –ATPase activity, the promotion of calcium channel activity by auxin was significantly inhibited. These results suggest that auxin promotes pollen tube growth via an effect on Ca 2+ channel activity in apical pollen tubes; however, this regulation is influenced by ATPase activity.