Respiration - Metabolism of Pollen Tubes

In the unpollinated pistils of Hippeastrum hybridum very high O₂, tension exists from stigma down through most of the style. During pollen tube growth a marked drop in O₂, tension takes place in the region of style containing the tips bf pollen tube and this drop in tension moves down progressively with the growth of the pollen tubes. However, after the passage of the tube, the original high level is restored, though not completely. It appears that the tube grows aerobically through the stigmatic and stylar tissues and only in the lower most regions of the style and ovary that the tube confronts anaerobic condition.