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Minerva Biotecnologica 2001 March;13(1):37-9


language: English

Rhizospheric bacteria promote sunflower (Helianthus annuus L.) plant growth and tolerance to heavy metals

Shilev S. I. 1, Ruso J. 2, Puig A. 4, Benlloch M. 3, Jorrin J. 2, Sancho E. 1

1 Department of Microbiology, ETSIAM, Universidad de Córdoba, Cordoba, Spain; 2Department of Biochemistry and Molecular Biology, ETSIAM, Universidad de Córdoba, Cordoba, Spain; 3 Department of Agronomy, ETSIAM, Universidad de Córdoba, Cordoba, Spain; 4 Department of Microbiology, Centro de Investigación y Formación Agrária, Cordoba, Spain, EMIR-UCO (Multidisciplinary Research Project on Phytoremediation), Agronomy and Forest Science High Technical School, University of Córdoba, Córdoba, Spain


Background. It is ­known ­that rhiz­os­pher­ic micror­gan­isms ­increase tol­er­ance to bio­tic and abi­ot­ic stress­es, in gen­er­al, and to ­heavy met­als, in par­tic­u­lar. As ­part of mul­ti­dis­ci­pli­nary ­research pro­ject on phy­tor­e­me­di­a­tion, car­ried out at the ­EMIR-UCO ­group, involve­ment of rhiz­os­pher­ic bac­te­ria on ­plant tol­er­ance to tox­ic met­als has ­been eval­u­at­ed.
Methods. Different bac­te­ria pop­u­la­tions ­have ­been ­obtained ­from ­roots and sur­round­ing ­soil in a met­al con­tam­i­nat­ed ­area (Aznalcóllar, Southern Spain). These pop­u­la­tions ­have ­been char­ac­ter­ized ­with ­respect to ­their tol­er­ance to ­heavy met­als (As, Pb, Cd, Zn, and Cu). Six, out of the 60 pop­u­la­tions eval­u­at­ed, ­have ­been select­ed ­because ­of their abil­ity to tol­er­ate the max­i­mum dos­es test­ed. Tolerance was gen­er­al and not selec­tive to spe­cif­ic met­als. By ­using sun­flow­er as experi­men­tal mod­el ­system in green­house experi­ments, the ­effects of the met­al tol­er­ant bac­te­ria pop­u­la­tions on ­plant ­growth, ­plant tol­er­ance and ­heavy met­als accu­mu­la­tion ­have ­been eval­u­at­ed.
Results. Higher ­growth and bio­mass devel­op­ment ­were ­obtained ­when the select­ed bac­te­ria ­were add­ed to the ­soil. At the high­est met­al dos­es, a reduc­tion in chlo­ro­phyll con­tent was occa­sion­al­ly ­observed, ­being ­these symp­toms clear­ly man­i­fest­ed in treat­ments ­with addi­tion of select­ed bac­te­ria. With ­respect to ­heavy met­als accu­mu­la­tion, an ­increase in met­al ­uptake and/or trans­lo­ca­tion to the aer­i­al ­part of the ­plants was meas­ured, ­being ­this clear­ly affect­ed in the ­case of the addi­tion of Zn, in the pres­ence of select­ed bac­te­ria.
Conclusions. Work in ­progress, is now ­focused in the iden­tifi­ca­tion of the dif­fer­ent bac­te­ria pop­u­la­tions, and the elu­ci­da­tion of mech­a­nisms ­involved in the ­increased tol­er­ance of met­als in ­plants in the pres­ence of ­mixed select­ed pop­u­la­tions.

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