Ethylene regulates ascorbic acid content during dark-induced leaf senescence

The aim of this work was to determine if changes in antioxidant contents are directly controlled by ethylene or are indirect effects associated with modulation of leaf senescence. Detached spinach (Spinacia oleracea L. cv Bison) leaves were treated with ethephon to induce ethylene production, placed in polyethylene bags and stored under darkness at 23 °C for 3 days. The ethephon treatment produced a rapid decrease on ascorbic acid (AA) content and an increase in its oxidised state before any leaf senescence parameters changed. Both AA synthesis and recovery from oxidised forms were affected by ethylene. In addition, leaves from Arabidopsis (Arabidopsis thaliana (L.) Heynh) ethylene insensitive mutants (ein2-1, ein3-1 and ein4) presented higher AA content than leaves from wt plants before dark storage. Furthermore, ein3-1 and ein4 but not ein2-1, showed slower leaf AA content declining than wt plants under dark-induced leaf senescence. The Arabidopsis mutant with constitutive triple response (ctr1-1) showed lower leaf AA content than wt plants but similar AA degradation rate with a higher oxidised state after dark storage for 3 days. These results demonstrate that ethylene is an important factor controlling AA content in mature leaves.