Peter Schopfer

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Germination of radish (Raphanus sativus cv Eterna) seeds can be inhibited by far-red light (high-irradiance reaction of phytochrome) or abscisic acid (ABA). Gibberellic acid (GA3) restores full germination under far-red light. This experimental system was used to investigate the release of reactive oxygen intermediates (ROI) by seed coats and embryos during(More)
Hydroxyl radicals (OH) are capable of unspecifically cleaving cell-wall polysaccharides in a site-specific reaction. I investigated the hypothesis that cell-wall loosening underlying the elongation growth of plant organs is controlled by apoplastically produced OH attacking load-bearing cell-wall matrix polymers. Isolated cell walls (operationally,(More)
 Using the tetrazolium salt XTT (Na,3′-[(phenylamino)-carbonyl]-3,4-tetrazolium]-bis(4-methoxy-6-nitro)benzenesulfonic acid hydrate) as a sensitive and physiologically compatible probe for the determination of superoxide (O2 ·−) production in vivo, we have shown that maize (Zea mays L.) coleoptiles possess the capacity of generating O2 ·− in the apoplastic(More)
Peroxidases catalyze the dehydrogenation by hydrogen peroxide (H2O2) of various phenolic and endiolic substrates in a peroxidatic reaction cycle. In addition, these enzymes exhibit an oxidase activity mediating the reduction of O2 to superoxide (O2.-) and H2O2 by substrates such as NADH or dihydroxyfumarate. Here we show that horseradish peroxidase can also(More)
Hydroxyl radicals ( · OH), produced in the cell wall, are capable of cleaving wall polymers and can thus mediate cell wall loosening and extension growth. It has recently been proposed that the biochemical mechanism responsible for · OH generation in the cell walls of growing plant organs represents an enzymatic reaction catalyzed by apoplastic peroxidase(More)
Reactive oxygen intermediates, i.e. the superoxide radical ( $${\rm O}_2^{ \cdot - } $$ ), hydrogen peroxide (H2O2) and the hydroxyl radical ( $${}^ \cdot {\rm OH}$$ ), are generally regarded as harmful products of oxygenic metabolism causing cell damage in plants, animals and microorganisms. However, oxygen radical chemistry may also play a useful role in(More)
Growth of turgid cells, defined as an irreversible increase in cell volume and surface area, can be regarded as a physical process governed by the mechanical properties of the cell wall and the osmotic properties of the protoplast. Irreversible cell expansion is produced by creating a driving force for water uptake by decreasing the turgor through stress(More)
Cell extension in the growing zone of plant roots typically takes place with a maximum local growth rate of 50% length increase per hour. The biochemical mechanism of this dramatic growth process is still poorly understood. Here we test the hypothesis that the wall-loosening reaction controlling root elongation is effected by the production of reactive(More)
As reactive oxygen species are important for many fundamental biological processes in plants, specific and sensitive techniques for their detection in vivo are essential. In particular, the analysis of hydroxyl radical (OH*) formation in biological reactions has rarely been attempted. Here, it is shown that spin trapping electron paramagnetic resonance(More)