Universidade de Lisboa Repositório da Universidade de Lisboa

Repositório da Universidade de Lisboa >
Faculdade de Ciências (FC) >
FC - Artigos em Revistas Internacionais >

Please use this identifier to cite or link to this item: http://hdl.handle.net/10451/4551

Title: Nitrogen assimilation and transport in carob plants
Authors: Cruz, C.
Lips, S. H.
Martins-Loução, M. A.
Keywords: Carob
Ceratonia siliqua
Charge balance
Nitrogen transport
Xylem loading
Issue Date: 1993
Publisher: Wiley-Blackwell
Citation: Physiologia Plantarum 89: 524-531. 1993
Abstract: Most of the nitrate reductase activity (80%;) in carob (Ceratonia siliqua L. cv. Mulata) is localised in the roots. The nitrate concentration in the leaves is relatively low compared to that in the roots, suggesting that nitrate influx into the leaf may be a major factor limiting the levels of nitrate reductase in the shoot. Transport of nitrate from root to shoot appears limited by the entrance of nitrate into the xylem. In order to study this problem, we determined the nitrate concentrations and nitrate reductase activities along the roots of nitrate-grown plants, as well as the composition of the xylem sap and the nitrate levels in the leaves. Some of the the bypocotyl, in order to bypass the loading of nitrate into the xylem of the roots. The results show that the loading of nitrate into the xylem is a limiting step. The cation and anion concentrations of nitrate- and ammonium-fed plants were similar, showing almost no production of organic anions. In both nitrate- and ammonium-fed plants, the transport of nitrogen from root to shoot was in the form of organic nitrogen compounds. The nitrate reductase activity in the roots was more than sufficient to explain all the efflux of OH− into the root medium of nitrate-fed plants. In carob plants the K-shuttle may thus be operative to a limited extent only, corresponding to between 11 and 27%; of the nitrate taken up. Potassium seems to be the cation accompanying stored nitrate in the roots of carob seedlings, since they accumulate nearly stoichiometric amounts of K+ and NO−3.
Description: This paper is part of the contributions to the Proceedings of the 3rd Internacional Symposium on Inorganic Nitrogen Assimilation, held in Tiberias, Israel, 6-11 September, 1992
Peer Reviewed: yes
URI: http://hdl.handle.net/10451/4551
ISSN: 0031-9317
Appears in Collections:FC - Artigos em Revistas Internacionais

Files in This Item:

File Description SizeFormat
00319317_524_531.pdf1.99 MBAdobe PDFView/Open
Restrict Access. You can request a copy!
Statistics
FacebookTwitterDeliciousLinkedInDiggGoogle BookmarksMySpaceOrkut
Formato BibTex mendeley Endnote Logotipo do DeGóis 

Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.

 

  © Universidade de Lisboa / SIBUL
Alameda da Universidade | Cidade Universitária | 1649-004 Lisboa | Portugal
Tel. +351 217967624 | Fax +351 217933624 | repositorio@reitoria.ul.pt - Feedback - Statistics
DeGóis
  Estamos no RCAAP Governo Português separator Ministério da Educação e Ciência   Fundação para a Ciência e a Tecnologia

Financiado por:

POS_C UE