Aplicação sequencial de etil-trinexapac e seus efeitos no eucalipto após períodos de deficiência hídrica e retorno da irrigação
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Data
2021-08-09
Autores
Gasparino, Larissa Soares
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Universidade Estadual Paulista (Unesp)
Resumo
Plantas de eucalipto são sensíveis aos estresses bióticos e abióticos durante seu crescimento inicial, sendo a deficiência hídrica o mais comum dentre os abióticos. Durante o período inicial de crescimento, trabalhos anteriores relataram que a aplicação de etil-trinexapac em baixas dosagens pode proporcionar um melhor desenvolvimento das plantas, o qual pode perdurar por até 90 dias após o plantio do eucalipto. Contudo, são escassos estudos que relatam o efeito deste produto em mudas de eucalipto após aplicação sequencial. Com isso, os objetivos foram determinar a melhor combinação de doses de etil-trinexapac para a aplicação sequencial em mudas de Eucalyptus urograndis (Clone 1407); bem como determinar a melhor época para aplicação do produto, após os períodos de deficiência hídrica e retorno da irrigação. Para tanto, dois experimentos foram conduzidos por 93 dias após o plantio em condições semicontroladas, em vasos de 25 L, preenchidos com uma mistura de solo e areia. Para ambos os experimentos, foram realizadas avaliações de florescência, teor de clorofila e trocas gasosas. A cada 10 dias foram avaliados a altura das plantas e diâmetro do caule. Ao final do período experimental (93 DAP), foi determinada a área foliar e a massa seca das folhas e caule. No primeiro experimento, os tratamentos foram dispostos em esquema fatorial 4x4, com um total de 80 parcelas experimentais. Os fatores foram constituídos por 4 doses (0, 30, 60 e 90 g i.a. ha-1) de etil-trinexapac aplicadas nas mudas de eucalipto ainda acondicionadas em tubetes, e 4 doses (0, 100, 150 e 200 g i.a. ha-1) de etil-trinexapac em aplicação sequencial, as quais foram realizadas aos 40 dias após o plantio (DAP). A aplicação de etil-trinexapac com dose inicial de 60 g i.a. ha-1 e sequencial de 150 g i.a. ha-1 foi a que promoveu um maior incremento (34,9%) de massa seca das plantas de eucalipto em relação à testemunha. Essa combinação de doses foi utilizada no segundo experimento. Os tratamentos consistiram de um fatorial 4x4+T, sendo 4 períodos de deficiência hídrica (0, 3, 6 e 9 dias) e 4 períodos (0, 3, 6 e 9 dias) de aplicação do produto após o retorno da irrigação, além do tratamento testemunha (sem aplicação de etil-trinexapac e sem deficiência hídrica). Conclui-se que a aplicação sequencial de etil-trinexapac nas doses de 60 e 150 g i.a. ha-1 foi capaz de prolongar o efeito estimulatório no crescimento de E. urograndis (Clone 1407) até os 93 DAP, com incrementos de até 34,9% na massa seca total, em relação à testemunha sem aplicação. Em mudas de eucalipto expostas a deficiência hídrica, a aplicação sequencial de etil-trinexapac proporcionou acúmulo de biomassa em comparação ao tratamento controle. De maneira geral, a melhor época para realizar a aplicação sequencial após períodos de estresse hídrico, é logo após o retorno da irrigação (0 dias).
Eucalypt plants are sensitive to biotic and abiotic stresses during initial growth, and water deficit is the most common among abiotics. During the period of initial development, previous studies have reported that the application of trinexapac-ethyl in low doses can lead to increased growth, which can last for up to 90 days after planting. However, there are few studies reporting the effect of this product on eucalypt seedlings after sequential application. Thus, the objectives were to determine the best combination of doses of trinexapac-ethyl for sequential application in Eucalyptus urograndis (Clone 1407) seedlings; as well as to understand the best time for trinexapac-ethyl application following periods of stress and irrigation return. Therefore, two experiments were carried out for 93 days after eucalyptus planting, under semi-controlled conditions, in 25 L pots, filled with a mixture of soil and sand. For both experiments: evaluations of Fv/Fm, chlorophyll content and gas exchange were performed. Every 10 days, plant height and stem diameter were evaluated. At the end of the experimental period (93 DAP), leaf area and dry mass of leaves and stem were determined. In the first experiment, the treatments were arranged in a 4x4 factorial scheme, with a total of 80 experimental plots. The factors consisted of 4 doses (0, 30, 60 and 90 g a.i. ha-1) of trinexapac-ethyl applied to eucalyptus seedlings still packed in tubes, and 4 doses (0, 100, 150 and 200 g a.i. ha-1) of trinexapac-ethyl in sequential application, which were carried out 40 days after planting (DAP). Trinexapac-ethyl application with an initial dose of 60 g a.i. ha-1 and a sequential dose of 150 g a.i. ha-1 promoted a greater increase (34.9%) in dry mass of the eucalyptus plants compared to control. This combination of doses was used in the second experiment. The treatments consisted of a 4x4+C factorial, with 4 periods of water deficit (0, 3, 6 and 9 days) and 4 periods (0, 3, 6 and 9 days) of trinexapac-ethyl application after the return of irrigation, in addition to the control treatment (without water deficit and trinexapac-ethyl application). It is concluded that the sequential application of trinexapac-ethyl at doses of 60 and 150 g a.i. ha-1 was able to prolong the stimulatory effect on the growth of Eucalyptus urograndis (Clone 1407) up to 93 DAP, with increments of up to 34.9% in the total dry mass, compared to the control without application. In eucalyptus seedlings exposed to water deficit, the sequential application of trinexapac-ethyl greater biomass accumulation compared to control. In general, the best time to perform the sequential application after periods of water stress is right after irrigation return (0 days).
Eucalypt plants are sensitive to biotic and abiotic stresses during initial growth, and water deficit is the most common among abiotics. During the period of initial development, previous studies have reported that the application of trinexapac-ethyl in low doses can lead to increased growth, which can last for up to 90 days after planting. However, there are few studies reporting the effect of this product on eucalypt seedlings after sequential application. Thus, the objectives were to determine the best combination of doses of trinexapac-ethyl for sequential application in Eucalyptus urograndis (Clone 1407) seedlings; as well as to understand the best time for trinexapac-ethyl application following periods of stress and irrigation return. Therefore, two experiments were carried out for 93 days after eucalyptus planting, under semi-controlled conditions, in 25 L pots, filled with a mixture of soil and sand. For both experiments: evaluations of Fv/Fm, chlorophyll content and gas exchange were performed. Every 10 days, plant height and stem diameter were evaluated. At the end of the experimental period (93 DAP), leaf area and dry mass of leaves and stem were determined. In the first experiment, the treatments were arranged in a 4x4 factorial scheme, with a total of 80 experimental plots. The factors consisted of 4 doses (0, 30, 60 and 90 g a.i. ha-1) of trinexapac-ethyl applied to eucalyptus seedlings still packed in tubes, and 4 doses (0, 100, 150 and 200 g a.i. ha-1) of trinexapac-ethyl in sequential application, which were carried out 40 days after planting (DAP). Trinexapac-ethyl application with an initial dose of 60 g a.i. ha-1 and a sequential dose of 150 g a.i. ha-1 promoted a greater increase (34.9%) in dry mass of the eucalyptus plants compared to control. This combination of doses was used in the second experiment. The treatments consisted of a 4x4+C factorial, with 4 periods of water deficit (0, 3, 6 and 9 days) and 4 periods (0, 3, 6 and 9 days) of trinexapac-ethyl application after the return of irrigation, in addition to the control treatment (without water deficit and trinexapac-ethyl application). It is concluded that the sequential application of trinexapac-ethyl at doses of 60 and 150 g a.i. ha-1 was able to prolong the stimulatory effect on the growth of Eucalyptus urograndis (Clone 1407) up to 93 DAP, with increments of up to 34.9% in the total dry mass, compared to the control without application. In eucalyptus seedlings exposed to water deficit, the sequential application of trinexapac-ethyl greater biomass accumulation compared to control. In general, the best time to perform the sequential application after periods of water stress is right after irrigation return (0 days).
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Eucalyptus, Hormesis, Irrigação