2,4-dichlorophenoxyacetic acid-induced leaf senescence in mung bean (Vigna radiata L. Wilczek) and senescence inhibition by co-treatment with silver nanoparticles

Thirupathi Karuppanapandian, Hong Wei Wang, Natarajan Prabakaran, Kandhavelu Jeyalakshmi, Mi Kwon, Kumariah Manoharan, Wook Kim

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Abstract

Leaf senescence induced by 2,4-dichlorophenoxyacetic acid (2,4-D) and senescence inhibition caused by supplementation with silver (Ag+) ions in the form of silver nitrate (AgNO3) or silver nanoparticles (AgNPs) were investigated in 8-day-old mung bean (Vigna radiata L. Wilczek) seedlings. Inhibition of root and shoot elongation were observed in mung bean seedlings treated with 500μM 2,4-D. Concomitantly, the activity of 1-aminocyclopropane-1-carboxylic acid synthase was significantly induced in leaf tissue. Leaf senescence induced by 2,4-D was closely associated with lipid peroxidation as well as increased levels of cytotoxic hydrogen peroxide (H2O2) and superoxide radicals (O2·-). Despite decreased catalase activity, the activities of peroxidase, superoxide dismutase, monodehydroascorbate reductase, dehydroascorbate reductase, and glutathione reductase were increased during 2,4-D-induced leaf senescence. Further, the levels of reduced ascorbate, oxidized ascorbate, and reduced glutathione were markedly decreased, whereas the level of oxidized glutathione increased. 2,4-D-induced leaf senescence in mung bean was accompanied by an increase in positive terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling, nuclear DNA fragmentation, and the activity of a 15-kDa Ca2+-dependent DNase. Supplementation with 100μM AgNO3 or AgNPs inhibited 2,4-D-induced leaf senescence. The present results suggest that increased oxidative stress (O2·- and H2O2) led to senescence in mung bean leaves. Furthermore, significantly induced antioxidative enzymes are not sufficient to protect mung bean cells from 2,4-D-induced harmful ROS.

Original languageEnglish
Pages (from-to)168-177
Number of pages10
JournalPlant Physiology and Biochemistry
Volume49
Issue number2
DOIs
Publication statusPublished - 2011 Feb 1

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Keywords

  • 2,4-Dichlorophenoxyacetic acid
  • Ethylene
  • Leaf senescence
  • Mung bean
  • Nuclear DNA fragmentation
  • Silver nanoparticles

ASJC Scopus subject areas

  • Physiology
  • Genetics
  • Plant Science

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