TRANSPORT OF 1-AMINOCYCLOPROPANE-1-CARBOXYLIC ACID (ACC) IN THE TRANSPIRATION STREAM OF TOMATO (LYCOPERSICON-ESCULENTUM) IN RELATION TO FOLIAR ETHYLENE PRODUCTION AND PETIOLE EPINASTY

We investigated the concentration and delivery of 1-aminocyclopropane- 1-carboxylic acid (ACC) in the transpiration stream of flooded and wel l-drained 1-month-old tomato plants (Lycopersicon esculentum Mill. cv. Ailsa Craig) over time in parallel with foliar ethylene production an d petiole epinasty. ACC was measured by gas chromatography using a nit rogen-phosphorus detector. Before analysis, roots of freshly detopped plants were pressurised pneumatically to make xylem sap flow at rates similar to those of whole plant transpiration. Delivery of ACC from ro ots to shoots of well-drained plants was sufficient to support basal e thylene production in shoots of unstressed plants. Delivery from flood ed, oxygen-deficient, roots increased after 6 h and coincided with the onset of epinastic leaf curvature. Further increases in ACC delivery and epinastic curvature occurred later in the photoperiod. After 24 h flooding, ACC delivery in xylem sap was 28 times more than in well-dra ined plants. This increased export of ACC from flooded roots was more than sufficient to account for the extra ethylene production in the sh oots and coincided with ACC accumulation in the leaves. Removing the s hoot before flooding did not reduce ACC export from oxygen-deficient r oots indicating that the ACC originated in roots and not the shoot. In creased ethylene production in petioles of flooded plants lagged 18 h behind epinasty.