Can trinexapac-ethyl stimulate the initial growth of eucalyptus?/Pode o etiltrinexapac estimular o crescimento de mudas de eucalipto?

Plant growth regulators and herbicides can act and modify several metabolic processes in plants. The use of sub-lethal doses of those compounds might modulate the development and growth of plants, an effect known as hormesis. Recent studies reported the stimulatory responses of sub-lethal doses of trinexapac-ethyl on the biomass accumulation and leaf area expansion of eucalypt plants. To date, there is no recommendation regarding promoting or inhibitory doses of such compounds for eucalypt production industry. Thus, this work aims to investigate the effect of trinexapac-ethyl on the establishment and initial growth of Eucalyptus urograndis seedlings. Trinexapacethyl was applied at doses varying 15 to 90 g (plus a control treatment) per hectare of active ingredient (g a.i. [ha.sup.-1]) in two application methods: spraying and root immersion. The doses of 15 g a.i. [ha.sup.-1] through spraying and the 30 g a.i. [ha.sup.-1] in root immersion resulted in a positive effect on the growth of Eucalyptus urograndis Clone GG100. Total dry biomass increased by 74.6% and 12.8%, respectively, compared to control plants. The spraying of 15 to 90 g a.i. [ha.sup.-1] of trinexapax-ethyl resulted in a stimulatory effect on the growth of eucalyptus. The doses of 15 and 30 g a.i. [ha.sup.-1] via root immersion provided a positive effect on the all evaluated characteristics of eucalyptus. The dose of 90 g a.i. [ha.sup.-1] resulted in an inhibitory effect on eucalyptus growth through root immersion at 35 days after the trinexapac-ethyl application.