Dual effect of 2, 4‐D on ethylene production and ripening of tomato fruit tissue

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Tomato fruits (Lycopersicon esculentum Mill. cv. Indian River) were treated with aqueous solutions of 2, 4‐dichlorophenoxyacetic acid (2, 4‐D) and the effects on respiration, ethylene production, and ripening were examined. 10‐3 and 10‐5M 2, 4‐D solutions were used. Dipping treatment of whole fruit picked at the 74% stage of development, gave an increase in respiration and ethylene production, the effect being directly related to 2, 4‐D concentration. Ripening was advanced relative to control fruit.Tomato disks cut from the pericarp tissue of fruit picked at the 81% stage of development were vacuum‐infiltrated with the same 2, 4‐D solutions. In these disks the increase in respiration continued longer compared to control disks. Ethylene production was considerably increased, and after an initial recovery the 2, 4‐D‐treated disks showed another increase at a much faster rate than controls. However, contrary to what could be expected from this increase in ethylene, ripening was delayed. Nevertheless, all disk samples showed advance ripening compared to whole fruit of the same age, indicating that they could not recover completely from the effect of cutting and treatment.The results showed that 2, 4‐D causes a dual effect in tomato fruit tissue: an increase in ethylene production which promotes ripening, and a delay in ripening. This last effect, depending on the uniformity of the auxin distribution and its concentration, prevails.