We investigated the concentration and delivery of
1-aminocyclopropane-1-carboxylic acid (ACC) in the transpiration stream of
flooded and well-drained 1-month-old tomato plants
(Lycopersicon esculentum Mill. cv. Ailsa Craig) over
time in parallel with foliar ethylene production and petiole epinasty. ACC was
measured by gas chromatography using a nitrogen–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 roots to shoots of well-drained plants was
sufficient to support basal ethylene production in shoots of unstressed
plants. Delivery from flooded, 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-drained
plants. This increased export of ACC from flooded roots was more than
sufficient to account for the extra ethylene production in the shoots and
coincided with ACC accumulation in the leaves. Removing the shoot before
flooding did not reduce ACC export from oxygen-deficient roots indicating that
the ACC originated in roots and not the shoot. Increased ethylene production
in petioles of flooded plants lagged 18 h behind epinasty.
The Role in Ozone Phytotoxicity of the Evolution of Ethylene upon Induction of 1-Aminocydopropane-1-carboxylic Acid Synthase by Ozone Fumigation in Tomato Plants