Abstract
ABSTRACT: Eucalyptus plants are sensitive to stress during their initial development, and water deficit is the most important one. Thus, the hormetic effect caused by the application of chemical products may be a factor that allows plants to tolerate such stresses. The objective of this study was to evaluate the effects of trinexapac-ethyl on the initial growth of Eucalyptus urophylla (Clone I-144), under water deficiency, at two application timings (before planting - BP; and after planting - AP). Two experiments were conducted simultaneously in a greenhouse for 74 days after planting (DAP) eucalyptus in 15 L pots. Treatments consisted of three trinexapac-ethyl doses (0.0, 30, and 60 g a.i. ha-1) and two water conditions (with and without water deficit). A complete randomized block design was used, in a 3 x 2 factorial arrangement, with five replications. At the BP application timing, trinexapac-ethyl was sprayed at 0 DAP, and at the AP timing, at 24 DAP. In both experiments, plant height, diameter, leaf area, dry matter, total relative chlorophyll content and gas-exchange were evaluated. There was a positive effect for the net CO2 assimilation rate at 27 and 40 DAP, for AP and BP, respectively. Eucalyptus plants, without water deficit, presented higher growth, regardless of the application timing. In conclusion, the application of trinexapac-ethyl before planting caused a positive effect on the height and diameter of eucalyptus; and the application timing influenced, in different ways, the evaluated characteristics, not having harmful effects on any of them.
Highlights
Eucalyptus is the most important crop in the Brazilian forestry sector, which generated 69.1 billion BRL in 2015, representing 1.2% of the country’s GDP
With the hypothesis that trinexapac-ethyl can provide positive responses to eucalyptus under conditions of abiotic stress, this work aimed at evaluating the effect of this chemical on the initial growth of E. urophylla under water deficit at two application timings
The average air temperature was 22.5 oC, with a relative average humidity of 61.4% and a 247-hour monthly sunshine. Both experiments were conducted during 74 days after planting (DAP) eucalyptus in 15 L pots, previously filled with a mixture of soil collected from the surface layer of a Dark Red Latosol (Table 1) and coarse sand in the ratio of 2:1 (v/v)
Summary
Eucalyptus is the most important crop in the Brazilian forestry sector, which generated 69.1 billion BRL in 2015, representing 1.2% of the country’s GDP. Several authors point out that the low availability of water in the soil has been the most important abiotic factor in the decrease of eucalyptus productivity (Chaves et al, 2009; Villar et al, 2011; Correia et al, 2014). This occurs because water deficit causes several physiological changes in plants, which, in an attempt to guarantee their survival, reduce growth, compromising productivity (Bedon et al, 2011). Studies that seek to elucidate ways to provide gains to eucalyptus, under stress conditions, should be stimulated
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