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EFFECT OF TRINEXAPAC-ETHYL IN EUCALYPTUS PRIMARY METABOLISM AND HORMONAL BALANCE UNDER DROUGHT STRESS CONDITIONS

Grant number: 19/13604-8
Support type:Scholarships abroad - Research Internship - Doctorate
Effective date (Start): November 01, 2020
Effective date (End): May 01, 2021
Field of knowledge:Agronomical Sciences - Agronomy - Plant Health
Principal Investigator:Pedro Luis da Costa Aguiar Alves
Grantee:Allan Lopes Bacha
Supervisor abroad: Esther Carrera Bergua
Home Institution: Faculdade de Ciências Agrárias e Veterinárias (FCAV). Universidade Estadual Paulista (UNESP). Campus de Jaboticabal. Jaboticabal , SP, Brazil
Local de pesquisa : Instituto de Biología Molecular y Celular de Plantas (IBMCP), Spain  
Associated to the scholarship:18/04376-9 - Effect of trinexapac-ethyl in eucalyptus primary metabolism and hormonal balance under drought stress, BP.DR

Abstract

Eucalyptus plants are sensitive to interferences imposed by stress factors during their initial growth, with water deficit being the most common among them. Previous studies have reported that trinexapac-ethyl may have a positive effect on the growth of eucalyptus seedlings, but there are no studies that have proven the occurrence of hormesis for this compound. Hormesis is a stimulatory effect caused by the application of low doses of a chemical that would be toxic in high amounts. The objective of this study is to verify the possible hormetic effect of trinexapac-ethyl on Eucalyptus urograndis (Clone 1407) seedlings under normal and water-deficient conditions and their effects on primary metabolism and eucalypt hormone balance. For this, two experiments will be conducted under semicontrolled conditions, in pots of 15 L, for 90 days after planting (DAP) of eucalyptus. The first experiment will consist of the application of eight doses of trinexapac-ethyl, namely: 0, 15, 30, 60, 90, 120, 150 and 300 g a.i. ha-1, and two water conditions (normal condition and under water deficiency, maintained at 40% of the field capacity), in five replications. The trinexapac-ethyl application will occur one day before eucalyptus planting. Evaluations of gas exchange, quantum efficiency of photosystem II (Fv/Fm) and total chlorophyll content will be performed in the first seven days after seedlings planting. Every two weeks, evaluations of eucalyptus height and diameter will be made. At the end of the experimental period (90 DAP), the leaf area and the dry masses of leaves and stems will be determined. The second experiment will be conducted in four replicates, in the same places and conditions of the first experiment, with the doses established by the results found; they are: Dose 0 = control without application; Dose 1 = the one that has the greatest positive effect on eucalyptus growth; and Dose 2 = the one that obtains similar growth to the control, being the greater dose that does not cause deleterious effect to the eucalyptus plants. Destructive assessments (along with collection of materials for analyzes of primary metabolism and hormonal quantification) will be performed at 5, 15, 30, 60 and 90 DAP. The destructive evaluations will consist of measuring the height, diameter, leaf area and dry masses of leaves and stems. In the first seven days after eucalyptus planting, gas exchange, Fv/Fm and relative chlorophyll content will be performed at the following times: 9:00 and 11:00 a.m.; 1:00, 3:00 and 5:00 p.m. The data will be submitted to analysis of variance by the F test and the means compared by the Tukey test at the 5% probability level, as well as submitted to the analysis of regression. For hormonal quantification in eucalyptus, the samples will be macerated in liquid nitrogen with addition of extraction solution and later added the internal standards of the respective hormones GAs, ABA, auxin, jasmonic acid and salicylic acid. After stirring, the samples will be centrifuged and the supernatant will be kept at rest. After addition of acetic acid, the mixture will be filtered on Oasis HLB® reverse phase columns. The readings will be made in high resolution mass spectrometer coupled to UHPLC. The hormonal analyzes will be carried out in the "Instituto de Biología Molecular y Celular de Plantas" (IBMCP) of the Universidad Politécnica de Valencia, Spain. For the analysis of compounds of the primary metabolism, the plant materials, at first, will be prepared in extracts for metabolites isolation and profiling. Subsequently, the samples will be fractionated in HPLC preparatory. All fractions collected will be analyzed by the LC-(DAD)-LTQ-Orbitrap Elite system, as well as by 1H Nuclear Magnetic Resonance. The analyzes of compounds of the primary metabolism will be carried out in partnership with the Chemistry Institute of UNESP of Araraquara-SP, with which the research group maintains a partnership.