Ethylene Evolution and Ammonium Accumulation by Tomato Plants after Root-Applied Glufosinate-Ammonium Treatment in the Presence of Ethylene Inhibitors

In previous research in hydroponics, ethylene evolution by tomato shoots (Lycopersicon esculentum Mill.) was promoted by the herbicidal action of root-applied glufosinate-ammonium (GLA). Ethylene evolution was preceded by accumulation and was detected before or concurrent with development of toxicity symptoms following GLA application. In the current experiment, aminooxyacetic acid (AOA) or silver thiosulfate (STS) was added in nutrient solutions to elucidate the relationship between accumulation, ethylene evolution, and symptom development. Aminooxyacetic acid is an inhibitor of ethylene synthesis, and STS is an inhibitor of ethylene action. In hydroponics, 4-week-old tomato seedlings were used. The GLA was added at 25 mg/L into Hoagland no. 1 nutrient solution. For the AOA and STS treatments, AOA or STS was added to concentrations of 1 mM or 25 mM, respectively. With GLA alone, foliar symptoms of injury appeared at 4 days after treatment (DAT), and plant death occurred at 10 DAT. Adding STS did not affect this process; however, AOA delayed the appearance of symptoms for 2 days, but plants died at 10 DAT. Neither AOA nor STS significantly affected plant mass relative to growth with GLA alone. With GLA alone, accumulated in shoots and roots at 2 DAT. The AOA inhibited accumulation in shoots until 6 DAT and in roots until 8 DAT. The STS had no effect on shoot accumulation relative to GLA alone but inhibited the accumulation in roots until 6 DAT. Herbicide-induced ethylene evolution occurred at 4 DAT without inhibitors and then fell. The AOA inhibited an increase in ethylene evolution during the period of the experiment, but STS had no inhibitory effect on the rise in ethylene production. This result suggests that AOA can inhibit ethylene evolution after accumulation and delay the development of toxicity symptoms. The STS had no effect on either accumulation or symptom appearance. The inhibitors did not prevent death of the plants exposed to GLA.