Journal of Food, Agriculture and Environment

Root redox-system activities and H₂O₂ – metabolizing enzymes in cucumber cultivars grown in conditions of iron deficit

Author(s):

Nadejda Babalakova ¹, Zeinab Salama ^2*, Snejka Rocheva ¹, Mohammed El-Fouly ³

Recieved Date: 2011-03-10, Accepted Date: 2011-10-09

Abstract:

The activities of root plasma membrane-associated reductases (RA), using Fe(III)citrate, Cu(II)citrate or hexacyanoferrate III (HCF) as electron acceptors were compared in two cucumber cultivars, grown hydroponically with normal iron supply or under iron starvation. Iron deficiency stress in the nutrient solution of cv. Corona induced two fold increase of Fe(III)citrate RA and about four fold increase of iron reduction, fulfilled by Gergana cv. roots. A high stimulation of Cu(II)citrate RA was registered in roots of both cultivars, and the similar enhancement of HCF III RA was demonstrated in conditions of iron deficit. Iron starvation responses in two cucumber cultivars included some different reactions of soluble antioxidant enzymes operating with hydrogen peroxide in roots and leaves. Activation of catalase (CAT) in Gergana roots was accompanied with its reduction in leaves, ascorbate-peroxidase (APX) activity increased in both roots and leaves and some reduction of root guaiacol peroxidase (G-POD) activity was followed with its stimulation in Gergana leaves. In the same time root CAT activity of Corona decreased to smaller extent in both roots and leaves, root G-POD was reduced by 40% but increase in leaves by the same percent and APX was stimulated in both tissues. No correlation could be found between soluble Fe falling in roots and leaves of both cultivars under iron deficiency and enzyme activity changes. Hydrogen peroxide content in leaves of both cultivars increased about 20% after iron exclusion, and root H₂O₂ production correlated to some extent with different alteration of CAT activity in cucumber cultivars. MDA as lipid peroxidation product increased significantly in roots of both cultivars, due to iron starvation, but some decrease was registered in leaves. Redox-system activities stimulation in Gergana cv. might be connected with stronger medium acidification and sooner appearance of iron starvation symptoms like higher reduction of root fresh weight. Corona expressed weaker reaction after iron exclusion from the nutrient medium with some tolerance in roots but demonstrated higher sensitivity to development of initial leaf chlorosis in conditions of iron deficiency.

Keywords:

Iron deficit, Cucumis sativum L., cucumber, root plasma membrane reductases, guaiacol- and ascorbate-peroxidases, catalase, hydrogen peroxide and MDA content, soluble iron content

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Journal: Journal of Food, Agriculture and Environment
Year: 2011
Volume: 9
Issue: 3&4
Category: Agriculture
Pages: 533-537

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