JXB Advance Access published online on November 11, 2009
Journal of Experimental Botany, doi:10.1093/jxb/erp321
© 2009 The Author(s).
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RESEARCH PAPER |
A different role for hydrogen peroxide and the antioxidative system under short and long salt stress in Brassica oleracea roots

Department of Abiotic Stress and Plant Pathology, CEBAS-CSIC, PO Box 164, Murcia, Spain
To whom correspodence should be addressed. E-mail: eolmos{at}cebas.csic.es
Salinity affects normal growth and development of plants depending on their capacity to overcome the induced stress. The present study was focused on the response and regulation of the antioxidant defence system in Brassica oleracea roots under short and long salt treatments. The function and the implications of hydrogen peroxide as a stressor or as a signalling molecule were also studied. Two different zones were analysed—the elongation and differentiation zone and the fully differentiated root zone—in order to broaden the knowledge of the different effects of salt stress in root. In general, an accumulation of hydrogen peroxide was observed in both zones at the highest (80 mM NaCl) concentration. A higher accumulation of hydrogen peroxide was observed in the stele of salt-treated roots. At the subcellular level, mitochondria accumulated hydrogen peroxide in salt-treated roots. The results confirm a drastic decrease in the antioxidant enzymes catalase, ascorbate peroxidase, and peroxidases under short salt treatments. However, catalase and peroxidase activities were recovered under long salt stress treatments. The two antioxidant molecules analysed, ascorbate and glutathione, showed a different trend during salt treatments. Ascorbate was progressively accumulated and its redox state maintained, but glutathione was highly accumulated at 24 h of salt treatment, but then its concentration and redox state progressively decreased. Concomitantly, the antioxidant enzymes involved in ascorbate and glutathione regeneration were modified under salt stress treatments. In conclusion, the increase in ascorbate levels and the maintenance of the redox state seem to be critical for root growth and development under salt stress.
Key words: Antioxidant, ascorbic acid, Brassica oleracea, glutathione, hydrogen peroxide, salt stress
* These authors contributed equally to this work.
Received 28 July 2009; Revised 14 October 2009 Accepted 19 October 2009