Free radical mediated mechanisms in stress and development in in vitro crop plant systems

  • Linda Adams

    Student thesis: Doctoral Thesis


    Aldehydic lipid peroxidation products, free radical mediated oxidative stress and antioxidant status were investigated in three in vitro plant systems with the objective of exploring the involvement of oxidative stress in plant tissue cultures. Daucus carota was used as a model system for the study of somatic embryogenesis and for the development of an enzyme linked immunosorbant assay (ELISA) technique, for the detection of hydroxynonenal-protein adducts in plant extracts. This study shows for the first time, in plants, that exogenously applied lipid peroxidation products hydroxynonenal (HNE) and malondialdehyde (MDA) inhibit callus proliferation and development (as somatic embryogenesis). Removal of the aldehydes led to a reversal of inhibitory effects.

    For the first time, HNE and MDA were measured in extracts of callus generated from different explants of Ipomoea batatas (an economically significant crop species). Using ELISA, HNE-protein adducts have been detected, in extracts from all three cultivars of I. batatas tested. Increases in the activities of the antioxidants, catalase and peroxidase were also observed in nodes of I. batatas after transfer to callus induction medium. 
    Three callus cultures of Glycine max, one of which was habituated against benzylamino purine, the second contained chlorophyll (green) and the third, devoid of chlorophyll (white) were profiled for lipid peroxidation products and antioxidant activity. This is first report of the detection free HNE and MDA in G. max and were detected in all three callus types, with the highest concentrations for both aldehydes in the habituated callus line. HNE-protein adducts were only detected in the white callus line of G. max. The level of hydroxyl radical activity was found to be increased in aged callus compared to callus taken from the mid-point of the subculture cycle. Low activities of catalase, peroxidase and other antioxidants were found in the habituated callus. It is proposed that increased amounts of hydroxyl radicals, high levels of HNE and MDA and the low activity of antioxidants leads to oxidative stress in extreme conditions such as habituation in in vitro plant systems. This study has implications regarding the understanding of in vitro plant recalcitrance.
    Date of AwardMay 2000
    Original languageEnglish

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