The effects of flooding on the export of gibberellins from the root to the shoot.

Gibberellin (GA)-like substances are shown to be present in the bleeding sap of tomatoes. It is demonstrated that these substances can promote stem elongation in intact tomato plants. Waterlogging of the root system inhibits stem growth and severely reduces the export of GAs from the root to the shoot in the xylem sap. It is suggested that decline in growth rate following waterlogging may, in part, be due to the reduction in the supply of GAs to the shoot.