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Type: Artigo de periódico
Title: Aerenchyma formation and recovery from hypoxia of the flooded root system of nodulated soybean
Author: Thomas, AL
Guerreiro, SMC
Sodek, L
Abstract: Background and Aims Flooding results in hypoxia of the root system to which N-2 fixation of nodulated roots can be especially sensitive. Morphological adaptions, such as aerenchyma formation, can facilitate the diffusion of oxygen to the hypoxic tissues. Using soybean, the aim of the study was to characterize the morphological response of the nodulated root system to flooding and obtain evidence for the recovery of N metabolism. Methods Sections from submerged tissues were observed by light microscopy, while sap bleeding from the xylem was analysed for nitrogenous components. Key Results Flooding resulted in the rapid formation of adventitious roots and aerenchyma between the stem (immediately above the water line), roots and nodules. In the submerged stem, taproot, lateral roots and adventitious roots, lysigenous aerenchyma arose initially in the cortex and was gradually substituted by secondary aerenchyma arising from cells derived from the pericycle. Nodules developed aerenchyma from cells originating in the phellogen but nodules situated at depths greater than 7-8 cm showed little or no aerenchyma formation. As a result of aerenchyma formation, porosity of the taproot increased substantially between the 4th and 7th days of flooding, coinciding with the recovery of certain nitrogenous products of N metabolism of roots and nodules transported in the xylem. Thus, on the first day of flooding there was a sharp decline in xylem ureides and glutamine (products of N-2 fixation), together with a sharp rise in alanine (product of anaerobic metabolism). Between days 7 and 10, recovery of ureides and glutamine to near initial levels was recorded while recovery of alanine was partial. Conclusions N metabolism of the nodulated soybean root system can recover at least partially during a prolonged period of flooding, a process associated with aerenchyma formation.
Subject: Glycine max
secondary aerenchyma
oxygen deficiency
nitrogen metabolism
nitrogen fixation
Country: Inglaterra
Editor: Oxford Univ Press
Rights: fechado
Identifier DOI: 10.1093/aob/mci272
Date Issue: 2005
Appears in Collections:Artigos e Materiais de Revistas Científicas - Unicamp

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