Differential response of young and adult leaves to herbicide 2,4‐dichlorophenoxyacetic acid in pea plants: role of reactive oxygen species

• Published in: Plant, cell and environment cell and environment, 2011-11, Vol.34 (11), p.1874-1889
• Main Authors: PAZMIÑO, DIANA M., RODRÍGUEZ‐SERRANO, MARÍA, ROMERO‐PUERTAS, MARÍA C., ARCHILLA‐RUIZ, ANGUSTIAS, DEL RÍO, LUIS A., SANDALIO, LUISA M.
• Format: Article
• Language: English
• Subjects: 2,4-Dichlorophenoxyacetic acid; 2,4-Dichlorophenoxyacetic Acid - toxicity; acyl‐CoA oxidase; antioxidants; Antioxidants - metabolism; Ascorbic Acid - metabolism; Biological and medical sciences; Biomarkers - metabolism; epinasty; imaging; Ethylenes - metabolism; Fatty acids; Fundamental and applied biological sciences. Psychology; Gene Expression Regulation, Plant - drug effects; Glutathione - metabolism; Herbicides; Hydrogen Peroxide - metabolism; Lipids; lipoxygenase; nitric oxide; oxidative stress; senescence; xanthine oxidoreductase; Models, Biological; Movements; Oxidative Stress - drug effects; Oxygen; Phenotype; Pisum sativum; Pisum sativum - drug effects; Pisum sativum - enzymology; Pisum sativum - growth & development; Pisum sativum - ultrastructure; Plant Leaves - drug effects; Plant Leaves - enzymology; Plant Leaves - growth & development; Plant Leaves - ultrastructure; Plant physiology and development; Plant Proteins - genetics; Plant Proteins - metabolism; Proteins; Reactive Oxygen Species - metabolism; senescence; Senescence and abscission; Stress; Toxicity; Vegetative apparatus, growth and morphogenesis. Senescence
• ISSN: 0140-7791; 1365-3040
• DOI: 10.1111/j.1365-3040.2011.02383.x

ABSTRACT In this work the differential response of adult and young leaves from pea (Pisum sativum L.) plants to the herbicide 2,4‐dichlorophenoxyacetic acid (2,4‐D) (23 mm) applied by foliar spraying was investigated. The concentration of 2,4‐D (23 mm) and the time of treatment (72 h) were previously optimized in order to visualize its toxic effects on pea plants. Under these conditions, the herbicide induced severe disturbances in mesophyll cells structure and proliferation of vascular tissue in young leaves and increased acyl‐CoA oxidase (ACX), xanthine oxidase (XOD) and lipoxygenase (LOX) activities in young leaves, and only ACX and LOX in adult leaves. This situation produced reactive oxygen species (ROS) over‐accumulation favoured by the absence of significant changes in the enzymatic antioxidants, giving rise to oxidative damages to proteins and membrane lipids. An increase of ethylene took place in both young and adult leaves and the induction of genes encoding the stress proteins, PRP4A and HSP 71,2, was observed mainly in young leaves. These results suggest that ROS overproduction is a key factor in the effect of high concentrations of 2,4‐D, and ROS can trigger a differential response in young and adult leaves, either epinasty development in young leaves or senescence processes in adult tissues. In this work, it has been evidenced that reactive oxygen species (ROS) overproduction is a key point in the effect of high concentrations of 2,4‐D, being peroxisomal fatty acid β‐oxidation one of the main sources, in addition to xanthine oxidase. ROS have a differentiated role in young and adult tissue, being involved in epinasty in young leaves, and senescence in old leaves. Ethylene can also be involved in epinasty and senescence and could contribute to ROS production. The role of ROS in epinasty is related with cell wall expansion, vascular tissue proliferation and oxidative processes which can affect the cytoskeleton giving rise to the curly of leaves. The oxidative burst caused by 2,4‐D leads to the activation of some stress and defence proteins such as PRP4‐A and HSP 71.1, which could contribute to mitigate damages induced by the herbicide.