Aspectos fisiológicos, bioquímicos, morfológicos, anatômicos e condutividade hidráulica associados à tolerância à seca em genótipos de Eucalyptus spp.
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2022-10-24
Autores
Zanatto, Bruna [UNESP]
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Universidade Estadual Paulista (Unesp)
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As secas têm aumentado globalmente, diminuindo a produtividade e, ou causando a mortalidade de árvores nos últimos anos, afetando o desempenho de plantios operacionais de Eucalyptus spp. Nesse sentido, o objetivo geral deste trabalho foi avaliar características fisiológicas, bioquímicas, morfológicas, anatômicas e a condutividade hidráulica da raiz e caule de sete genótipos de Eucalyptus spp. cultivados em diferentes condições de disponibilidade hídrica, na fase de mudas e plantas em campo, e associá-las com a tolerância à deficiência hídrica. O trabalho foi dividido em três experimentos, sendo o primeiro experimento realizado com mudas de cada genótipo para a avaliação da condutividade hidráulica da raiz, obtida através da medição do fluxo de seiva e normalizada pela massa seca de raiz e a condutividade hidráulica potencial, através das medições dos diâmetros e densidade de vasos. O segundo experimento foi implantado com mudas com aproximadamente 90 dias, em delineamento de blocos casualizados com os sete genótipos de Eucalyptus spp. submetidos a dois regimes hídricos. O regime hídrico 1 (RH1) correspondeu a 60% e o regime 2 (RH2) a 30% da capacidade máxima de retenção de água pelo solo. Foram avaliadas características biométricas, fisiológicas, bioquímicas e anatômicas de folha e caule. E o terceiro experimento foi realizado com a madeira dos sete genótipos amostradas em duas Zonas Climáticas e em duas faixas de idade (aproximadamente aos 2 e aos 5,5 anos). Nas amostras das madeiras foram avaliados os diâmetros com casca, a densidade aparente, feitas a caracterização anatômica do xilema, determinações da composição química e da condutividade hidráulica potencial. Os dados foram submetidos à análise de variância, segundo delineamentos adequados, com comparação de medias pelo teste de Tukey a 5% de probabilidade e análise multivariada de agrupamento pelo método de Ward e de dispersão por Componentes Principais. No primeiro experimento, comparando os dois métodos de avaliação da condutividade hidráulica, condutividade real e potencial, verificou-se que os resultados foram concordantes, apontando o genótipo G3 como de maior condutividade, G6 e G2 com condutividades intermediárias e G5 e G7 com menores valores de condutividade. Os resultados obtidos no segundo experimento demonstram que os genótipos apresentam redução na abertura, comprimento, largura e densidade dos estômatos, no diâmetro dos vasos e na condutividade hidráulica, sob menor disponibilidade hídrica. No RH2, os genótipos G1 e G2 aumentaram a densidade e diminuíram o diâmetro dos vasos, em comparação com o regime sem limitação hídrica, o que poderia num primeiro momento demonstrar segurança hidráulica sob menor disponibilidade hídrica. Porém de forma oposta ao G2, G1 apresentou maior diâmetro de vasos e condutividade hidráulica potencial sob limitação hídrica, o que indica serem genótipos com comportamentos e estratégias distintas para enfrentarem uma situação de deficiência hídrica. Houve redução na condutividade hidráulica do RH1 para o RH2 em todos os genótipos, mas em menor proporção para o G1, que se mostrou mais estável à diminuição da disponibilidade hídrica. No terceiro experimento observou-se que os genótipos não apresentam tendência clara de desempenho frente aos ambientes avaliados, mas a idade de avaliação foi determinante para a discriminação dos grupos. No ambiente mais restritivo, constituído pela idade de 5,22 a 6 anos na Zona Climática 2 (Ambiente 4), e para o conjunto dos caracteres avaliados, os genótipos se dividem em três grupos em que G1 e G7 apresentam maior segurança hidráulica e tolerância à seca, G4 e G5 têm comportamentos intermediários e G2 e G3 têm menor tolerância à seca e segurança hidráulica. Apesar de não estar presente nessa condição, G6 apresentou nos demais ambientes avaliados, características intermediárias de tolerância à seca.
Droughts have increased globally, decreasing productivity and/or causing tree mortality in recent years, affecting the performance of commercial Eucalyptus spp plantations. In this sense, the general objective of this work was to evaluate physiological, biochemical, morphological and anatomical characteristics and the hydraulic conductivity of the root and stem of seven genotypes of Eucalyptus spp. cultivated under different conditions of water availability, in the seedlings and plants stage in the field, and to associate them with the tolerance to the water deficit. The work was divided into three experiments, the first experiment carried out with seedlings of each genotype to evaluate the root hydraulic conductivity, obtained by measuring the sap flow and normalized by the root dry mass and the potential hydraulic conductivity, through measurements of vessel diameters and density. The second experiment was implanted with seedlings with approximately 90 days, in a randomized block design with the seven genotypes of Eucalyptus spp. subjected to two water regimes. Water regime 1 (WR1) corresponded to 60% and regime 2 (WH2) to 30% of the maximum soil water retention capacity. Biometric, physiological, biochemical and anatomical characteristics of leaf and stem were evaluated. And the third experiment was carried out with the wood of the seven genotypes sampled in two Climatic Zones and in two age groups (approximately 2 and 5.5 years old). In the wood samples, the diameters with bark, the apparent density, the anatomical characterization of the xylem, determinations of the chemical composition and the potential hydraulic conductivity were evaluated. Data were submitted to analysis of variance, according to suitable designs, with comparison of means by Tukey's test at 5% probability and multivariate analysis of clustering by Ward method and dispersion by Principal Components. In the first experiment, comparing the two methods of evaluation of hydraulic conductivity, real and potential conductivity, it was found that the results were in agreement, indicating the genotype G3 as having the highest conductivity, G6 and G2 with intermediate conductivities and G5 and G7 with lower values of conductivity. The results obtained in the second experiment show that the genotypes exhibit a reduction in stomata opening, length, width and density, in vessel diameter and in hydraulic conductivity, under lower water availability. In WH2, the genotypes G1 and G2 increased the density and decreased the diameter of the vessels, compared to the regime without water limitation, which could at first demonstrate hydraulic security under lower water availability. However, in an opposite way to G2, G1 presented higher vessel diameter and higher hydraulic conductivity under water restriction, which indicates that they are genotypes with different behaviors and strategies to confront a situation of water deficit. There was a reduction in the hydraulic conductivity from WH1 to WH2 in all genotypes, but to a lesser extent for G1, which showed to be more stable to the decrease in water availability. In the third experiment, it was observed that the genotypes do not present a clear trend of performance against the evaluated environments, but the age of evaluation was decisive for the discrimination of the groups. In the more restrictive environment, constituted by the age of 5.22 to 6 years in Climatic Zone 2 (Environment 4), and for the set of evaluated characters, the genotypes are divided into three groups in which G1 and G7 present greater hydraulic safety and tolerance to drought, G4 and G5 have intermediate behaviors and G2 and G3 have lower drought tolerance and hydraulic safety Despite not being present in this condition, G6 presented in the other evaluated environments, intermediate characteristics of drought tolerance.
Droughts have increased globally, decreasing productivity and/or causing tree mortality in recent years, affecting the performance of commercial Eucalyptus spp plantations. In this sense, the general objective of this work was to evaluate physiological, biochemical, morphological and anatomical characteristics and the hydraulic conductivity of the root and stem of seven genotypes of Eucalyptus spp. cultivated under different conditions of water availability, in the seedlings and plants stage in the field, and to associate them with the tolerance to the water deficit. The work was divided into three experiments, the first experiment carried out with seedlings of each genotype to evaluate the root hydraulic conductivity, obtained by measuring the sap flow and normalized by the root dry mass and the potential hydraulic conductivity, through measurements of vessel diameters and density. The second experiment was implanted with seedlings with approximately 90 days, in a randomized block design with the seven genotypes of Eucalyptus spp. subjected to two water regimes. Water regime 1 (WR1) corresponded to 60% and regime 2 (WH2) to 30% of the maximum soil water retention capacity. Biometric, physiological, biochemical and anatomical characteristics of leaf and stem were evaluated. And the third experiment was carried out with the wood of the seven genotypes sampled in two Climatic Zones and in two age groups (approximately 2 and 5.5 years old). In the wood samples, the diameters with bark, the apparent density, the anatomical characterization of the xylem, determinations of the chemical composition and the potential hydraulic conductivity were evaluated. Data were submitted to analysis of variance, according to suitable designs, with comparison of means by Tukey's test at 5% probability and multivariate analysis of clustering by Ward method and dispersion by Principal Components. In the first experiment, comparing the two methods of evaluation of hydraulic conductivity, real and potential conductivity, it was found that the results were in agreement, indicating the genotype G3 as having the highest conductivity, G6 and G2 with intermediate conductivities and G5 and G7 with lower values of conductivity. The results obtained in the second experiment show that the genotypes exhibit a reduction in stomata opening, length, width and density, in vessel diameter and in hydraulic conductivity, under lower water availability. In WH2, the genotypes G1 and G2 increased the density and decreased the diameter of the vessels, compared to the regime without water limitation, which could at first demonstrate hydraulic security under lower water availability. However, in an opposite way to G2, G1 presented higher vessel diameter and higher hydraulic conductivity under water restriction, which indicates that they are genotypes with different behaviors and strategies to confront a situation of water deficit. There was a reduction in the hydraulic conductivity from WH1 to WH2 in all genotypes, but to a lesser extent for G1, which showed to be more stable to the decrease in water availability. In the third experiment, it was observed that the genotypes do not present a clear trend of performance against the evaluated environments, but the age of evaluation was decisive for the discrimination of the groups. In the more restrictive environment, constituted by the age of 5.22 to 6 years in Climatic Zone 2 (Environment 4), and for the set of evaluated characters, the genotypes are divided into three groups in which G1 and G7 present greater hydraulic safety and tolerance to drought, G4 and G5 have intermediate behaviors and G2 and G3 have lower drought tolerance and hydraulic safety Despite not being present in this condition, G6 presented in the other evaluated environments, intermediate characteristics of drought tolerance.
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Palavras-chave
Estresse hídrico, Hydric stress, Eucalyptus, Plantas relações hidricas