Organ-specific effects of the auxin herbicide 2,4-D on the oxidative stress and senescence-related parameters of the stems of pea plants |
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Authors: | Iva McCarthy-Suárez Manuel Gómez Luis A del Río José M Palma |
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Institution: | 1.Departamento de Bioquímica, Biología Celular y Molecular de Plantas,Estación Experimental del Zaidín,Granada,Spain;2.Departamento de Biología del Desarrollo, Instituto de Biología Molecular y Celular de Plantas,CSIC-Universidad Politécnica de Valencia,Valencia,Spain |
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Abstract: | Oxidative stress and senescence have been shown to participate in the toxicity mechanism of auxin herbicides in the leaves
and roots of sensitive plants. However, their role in stem toxicity has not been studied yet. In this work, we report the
effect of foliar or root applications of the auxin herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) on the parameters of oxidative
stress and senescence of stems of pea (Pisum sativum L.) plants. Contrary to their effect on the pea leaves, in the stems 2,4-D applications did not cause oxidative stress, as
shown by the parameters of lipid peroxidation, protein carbonyls, and total and protein thiols. Moreover, they inhibited the
superoxide radical (O2.−)-producing xanthine oxidase (XOD) activity and stimulated the antioxidant activities of catalase (CAT), guaiacol peroxidase
(GPOX), ascorbate peroxidase (APX), glutathione reductase (GR), glutathione S-transferase (GST) and Krebs cycle NAD+-isocitrate dehydrogenase (IDH). Applications of 2,4-D also did not induce senescence in the pea stems, as shown by the increase
of proteins, the lack of stimulation of proteolytic activity, and the inhibition of senescence-related isocitrate lyase (ICL)
activity. However, they stimulated the H2O2-producing acyl-CoA oxidase (ACOX) activity of fatty acid beta oxidation. Results suggest that oxidative stress and senescence
are not involved in the mechanism of toxicity of 2,4-D in the stems of pea plants, and that these phenomena are not whole-plant
toxicity mechanisms for auxin herbicides in susceptible plants. Results also suggest that the effect of 2,4-D on the oxidative
metabolism of pea plants might be organ-specific. |
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