Abstract
Eucalyptus plants are sensitive to stress factors in the initial growth phase. The plant growth regulator trinexapac-ethyl can provide gains to eucalyptus plants, a phenomenon known as hormesis. Thus, the aim of this work was to evaluate the effect of trinexapac-ethyl on the initial growth of two Eucalyptus urograndis clones (Clone 1 = I-144 and Clone 2 = 1407). The experiment was performed during 90 days after planting (DAP) of eucalyptus, in 100 L pots, with a randomized complete block design. The treatments were arranged in a 2 × 3 factorial scheme, with two eucalyptus clones and three trinexapac-ethyl doses (0, 30 and 60 g i.a. ha-1), with four replications. Fortnightly, plants height and stem diameter were evaluated. At 90 DAP, the leaf area and plants dry matter (DM) were evaluated. Clone 1 obtained leaf area and total DM 53% and 58% larger than Clone 2, respectively. The higher dose of trinexapac-ethyl provided mean gains of 30% in stem DM and total DM in Clone 1. For Clone 2, both doses of the product caused mean gains of 70% in stem DM, leaf DM and total DM. In conclusion, trinexapac-ethyl has a positive effect on the initial growth of E. urograndis, Clones I-144 and 1407. Clone I-144 showed higher growth than Clone 1407, regardless trinexapac-ethyl application. However, the Clone 1407 obtained more expressive gains with the application of trinexapac-ethyl, compared to Clone I-144.
Highlights
The eucalyptus crop is the most important for the Brazilian forestry sector, which has considerable relevance in the country's economy, accounting for 1.2% of national GDP (Indústria Brasileira de Árvores [IBÁ], 2016)
With the hypothesis that different eucalyptus clones respond differently to trinexapac-ethyl, the present study aimed to evaluate the effect of trinexapac-ethyl on the initial growth of two Eucalyptus urograndis clones (Clone I-144 and Clone 1407)
For Clone 1 (I-144) plants height, no positive effect of trinexapac-ethyl was observed until 75 days after planting (DAP), in the last evaluation (90 DAP), the highest dose of the product provided an increase of 12.5% compared to the control (Figure 1-A)
Summary
The eucalyptus crop is the most important for the Brazilian forestry sector, which has considerable relevance in the country's economy, accounting for 1.2% of national GDP (Indústria Brasileira de Árvores [IBÁ], 2016). The hormetic effect is characterized as a stimulatory response resulting from the application of a chemical product that would be toxic in high quantities (Calabrese & Baldwin, 2002; Belz & Duke, 2014). This phenomenon has already been observed for several plant species and products, including trinexapac-ethyl in eucalyptus plants (Velini et al, 2008; Pereira, Nepomuceno, Pires, Parreira, & Alves, 2013; Pires, Pereira, Nepomuceno, & Alves, 2013; Correia & Villela, 2015)
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