Anatomia de raízes de Eucalyptus grandis Hill ex Maiden em diferentes profundidades do solo sob um contexto de redução de chuvas
Carregando...
Data
2016-02-26
Autores
Gomide, Maëla Peron [UNESP]
Título da Revista
ISSN da Revista
Título de Volume
Editor
Universidade Estadual Paulista (Unesp)
Resumo
Em espécies perenes de ambientes sazonais, o estabelecimento de um sistema radicular profundo é uma das estratégias de adaptação dessas espécies ao estresse hídrico. Nessas plantas, é bem estabelecido que a maior parte da absorção de água e íons ocorre em raízes finas não-suberizadas e que as porções mais jovens das raízes são as mais ativas nesse processo. Uma vez que modelos de mudança climática preveem uma redução de chuvas de até 20% entre a primeira e a última década do século XXI em grande faixa do globo terrestre, incluindo o Brasil, entender o efeito da redução da precipitação sobre a anatomia das raízes faz-se cada vez mais importante. O objetivo desse trabalho foi estudar a anatomia de raízes de Eucalyptus grandis em diferentes profundidades do solo e investigar o efeito da limitação da precipitação nos aspectos estruturais dessas raízes. Um delineamento experimental foi estabelecido em junho de 2010 com um clone de E. grandis em uma plantação da Estação Experimental de Ciências Florestais de Itatinga (EECFI), SP, Brasil. Dois tratamentos (dois regimes de água) foram aplicados em blocos separados de 2010 a 2014: tratamento TO (controle) sem a intercepção de chuvas e tratamento TR com interceptação de 37% das chuvas por lâminas de plástico transparente. Em 2014, trincheiras de até 17 metros de profundidade foram abertas no solo, sendo uma para cada tratamento. Cada trincheira foi centralizada entre quatro indivíduos de E. grandis. Raízes finas laterais foram coletadas a 0-50cm e 12-16m de profundidade do solo e separadas em quatro categorias de acordo com seu diâmetro: Ø > 2mm; 1< Ø ≤ 2mm; 0,5< Ø ≤ 1mm; e Ø ≤ 0,5mm. As amostras foram processadas segundo técnicas usuais em anatomia vegetal. Análises morfométricas foram realizadas em secções transversais ao microscópio de luz com auxílio do software Olympus Cell B. Os resultados foram submetidos ao teste t (de Student) e U-Mann Whitney; outros à ANOVA dois fatores e ao teste de Tukey. Raízes com diâmetro Ø > 2mm e 1< Ø ≤ 2mm coletadas em TR, e raízes com diâmetro 0,5 < Ø ≤ 1mm coletadas em TO nas maiores profundidades do solo apresentaram maior área total ocupada pelo xilema; raízes com diâmetro Ø > 2mm, 1< Ø ≤ 2mm e 0,5 < Ø ≤ 1mm coletadas em TR nas maiores profundidades também apresentaram maior proporção da área total ocupada pelo xilema pela área total da porção funcional da raiz; nas raízes profundas dessas três categorias coletadas em TO e TR os elementos de vaso eram menos abundantes, porém com maior diâmetro do que as raízes mais superficiais. O aumento do diâmetro dos elementos de vasos nas raízes profundas remete a um aumento da condutividade hidráulica, porém pode aumentar o risco de embolismo. Além disso, raízes profundas dessas mesmas três categorias coletadas em TR apresentaram numerosos grupos de fibras gelatinosas no floema e tilos nos elementos de vaso. Fibras gelatinosas apresentam potencial para armazenamento de água enquanto que tilos podem representar uma estratégia contra o embolismo em condições de estresse hídrico. Esses dados reforçam a ideia de que a redução de chuva influencia a anatomia das raízes de E. grandis nas camadas mais profundas do solo.
In perennial species the establishment of a deep root system is an adaptive strategy to water deficit. In these plants it is well established that most of the absorption of water and ions in perennial woody species occurs in fine non-suberized roots and that younger portions of roots are the most active in this process. Since models of climate changes predict a rainfall reduction in the next years of 20% until the first and the last decade of 21st century in global large scale, including Brazil, to understand the effect of rainfall reduction on the anatomy of these roots becomes even more important. This study aims to study the anatomy of Eucalyptus grandis roots at different soil depths investigating the effect of limiting the rainfall in structural aspects of these roots. An experiment was set up in June 2010 with a clone of Eucalyptus grandis used in commercial plantations by the Suzano Company in Estação Experimental de Ciências Florestais de Itatinga (EECFI), SP, Brazil. Two treatments (two water systems) were applied in separated blocks from 2010 to 2014: treatment TO (control) without rainfall interception and treatment TR (reduction) with 37% of rainfall interception by transparent plastic sheeting panels. In 2014, trenches of until 17 m of depth were opened in the soil, one for each treatment respectively. Each trench was centered between fours individuals of E. grandis. Fine lateral roots with were collected at 0-50cm and 12-16m of depth and separated in four categories according to their diameter: Ø > 2mm; 1< Ø ≤ 2mm; 0.5< Ø ≤ 1mm; e Ø ≤ 0.5mm. Samples were processed according to conventional techniques in plant anatomy. Morphometric analysis was performed in transversal sections at the light microscope Olympus BX 41 using the software Cell B. The results were submitted to the t-student test and U Mann-Whitney test; others to a two way ANOVA and Tukey test. Roots with diameter Ø > 2mm and 1< Ø ≤ 2mm collected in TR, and roots with diameter 0.5 < Ø ≤ 1mm collected in TO in greater depths of the soil presented biggest total area occupied by the xylem; roots with diameter Ø > 2mm, 1< Ø ≤ 2mm and 0.5 < Ø ≤ 1mm collected in TR in greater depths also presented biggest total area of xylem per total area of functional root portion ratio; in deep roots of these three categories collected in TO and TR the vessels were less abundant, however with larger diameter than superficial roots. The increase in diameter of vessels of deep roots refers to an increase in hydraulic conductivity, but can raise the risk of embolism. Furthermore, deep roots of those three categories collected in TR showed numerous groups of gelatinous fibers in the phloem and tyloses in the vessels. Gelatinous fibers have potential for storing water while tyloses may represent a strategy against embolism in water stress conditions. These data reinforce the idea that the reduction of rainfall influences the anatomy of the roots of E. grandis in the deepest layers of the soil.
In perennial species the establishment of a deep root system is an adaptive strategy to water deficit. In these plants it is well established that most of the absorption of water and ions in perennial woody species occurs in fine non-suberized roots and that younger portions of roots are the most active in this process. Since models of climate changes predict a rainfall reduction in the next years of 20% until the first and the last decade of 21st century in global large scale, including Brazil, to understand the effect of rainfall reduction on the anatomy of these roots becomes even more important. This study aims to study the anatomy of Eucalyptus grandis roots at different soil depths investigating the effect of limiting the rainfall in structural aspects of these roots. An experiment was set up in June 2010 with a clone of Eucalyptus grandis used in commercial plantations by the Suzano Company in Estação Experimental de Ciências Florestais de Itatinga (EECFI), SP, Brazil. Two treatments (two water systems) were applied in separated blocks from 2010 to 2014: treatment TO (control) without rainfall interception and treatment TR (reduction) with 37% of rainfall interception by transparent plastic sheeting panels. In 2014, trenches of until 17 m of depth were opened in the soil, one for each treatment respectively. Each trench was centered between fours individuals of E. grandis. Fine lateral roots with were collected at 0-50cm and 12-16m of depth and separated in four categories according to their diameter: Ø > 2mm; 1< Ø ≤ 2mm; 0.5< Ø ≤ 1mm; e Ø ≤ 0.5mm. Samples were processed according to conventional techniques in plant anatomy. Morphometric analysis was performed in transversal sections at the light microscope Olympus BX 41 using the software Cell B. The results were submitted to the t-student test and U Mann-Whitney test; others to a two way ANOVA and Tukey test. Roots with diameter Ø > 2mm and 1< Ø ≤ 2mm collected in TR, and roots with diameter 0.5 < Ø ≤ 1mm collected in TO in greater depths of the soil presented biggest total area occupied by the xylem; roots with diameter Ø > 2mm, 1< Ø ≤ 2mm and 0.5 < Ø ≤ 1mm collected in TR in greater depths also presented biggest total area of xylem per total area of functional root portion ratio; in deep roots of these three categories collected in TO and TR the vessels were less abundant, however with larger diameter than superficial roots. The increase in diameter of vessels of deep roots refers to an increase in hydraulic conductivity, but can raise the risk of embolism. Furthermore, deep roots of those three categories collected in TR showed numerous groups of gelatinous fibers in the phloem and tyloses in the vessels. Gelatinous fibers have potential for storing water while tyloses may represent a strategy against embolism in water stress conditions. These data reinforce the idea that the reduction of rainfall influences the anatomy of the roots of E. grandis in the deepest layers of the soil.
Descrição
Palavras-chave
Estresse hídrico, Eucalipto, Raízes profundas, Raízes superficiais, Xilema, Drought stress, Eucalyptus, Deep roots, Superficial roots, Xylem