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Universidade Estadual Paulista (UNESP) 2016

Anatomia de raízes de Eucalyptus grandis Hill ex Maiden em diferentes profundidades do solo sob um contexto de redução de chuvas

Gomide, Maëla Peron

Titre : Anatomia de raízes de Eucalyptus grandis Hill ex Maiden em diferentes profundidades do solo sob um contexto de redução de chuvas

Anatomy of Eucalyptus grandis W. Hill ex Maiden roots at different soil depths in a rainfall reduction context

Auteur : Gomide, Maëla Peron

Université de soutenance : Universidade Estadual Paulista (UNESP)

Grade : Mestre no Programa de Pós-Graduação em Ciências Biológicas (Botânica) 2016

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.(...)

Mots Clés  : Estresse hídrico Eucalipto Raízes profundas Raízes superficiais Xilema Drought stress Eucalyptus Deep roots Superficial roots Xylem


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