The effect of 5OH-1,4-Naphthoquinone on Norway spruce seeds during germination

• The effect of 5-OH-1,4-naphthoquinone (50H-NQ), a knowninhibitor of germination and growth and an inducer of oxidativestress, on seeds from Norway spruce (Picea abies) during germinationwas studied. 50H-NQ was activated by homogenate fromseeds to reactive species that reduce oxygen to superoxide radicalsin vitro. Increasing concentrations of 50H-NQ increased lipidperoxidation during this activation. Small effects of 50H-NQ ongermination of seeds were observed at concentrations up to 200Mm. However, higher concentrations, e.g. 500 and 1000 AM, exertedmore pronounced effects on seeds. These results suggest that theeffect of 50H-NQ was a delay rather than an inhibition of germination.However, the effect of 50H-NQ on postgerminative growthwas more potent than that on germination, and higher concentrationsinhibited growth >97%. These results suggest that the seedshave a very effective defense system against quinone and reactiveoxygen species, since the small effects of 50H-NQ on germinationand postgermination at concentrations up to 200 AM can be explainedby the formation of a metabolite of 50H-NQ that is not asreactive with oxygen as the original quinone. The 50H-NQ metabolitecollected during germination experiments showed differencesin its absorption spectrum in comparison with 50H-NQ, whichsuggest changes in structure. This metabolite was reduced byquinone reductase, but reduction of oxygen to superoxide radicalswas not detected during its activation with homogenate from seeds.This metabolite may arise via a conjugation reaction, since theaddition of 500 Mm uridine 5'-diphosphoglucuronic acid or 3'-phosphoadenosine-5'-phosphosulfate to the incubation mixtureduring activation of this metabolite by homogenate from seeds invitro inhibited reduction of oxygen to superoxide radicals by 50and 64%, respectively. The constitutive levels of superoxide dismutaseand catalase were sufficient to prevent oxygen toxicityduring activation of 50H-NQ, since these enzymes were not inducedwhen the seeds were treated with 200 AM 50H-NQ. 

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NATURVETENSKAP  -- Biologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences (hsv//eng)

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Biology

Biologi

Cell and Organism Biology

Cell- och organismbiologi

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