ISSN:
1399-3054
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Biology
Notes:
Uptake of O2 by whole, detached, root systems of wheat (Triticum aestivum L. cv. Alexandria) was titrated with salicylhydroxamic acid (SHAM) in the presence and absence of cyanide. The resulting Qall plot was non-linear indicating that SHAM was acting non-specifically. The nature of the non-specific effects was investigated in reverse titration experiments. Uptake of O2 was titrated with KCN in the presence and absence of SHAM at 1 mM and 25 mM, which yielded Qcy1 values of 〈 1 and 〉 1, respectively. The results suggest that at 25 mM, SHAM inhibits the cytochrome pathway, but at 1 mM it stimulates an O2-consuming process which is likely to be a peroxidase. A SHAM-stimulated peroxidase could easily be washed from these roots. In vitro, the peroxidase was stimulated to a similar extent by low (1 mM) and high (25 mM) concentrations of SHAM. Failure to inhibit with high concentrations of SHAM distinguishes this peroxidase from those bitherto eluted from root tissue. Reverse titration experiments in the presence and absence of 1 mM SHAM indicated that there were no significant side effects of SHAM in root tips. These data are supported by the negligible peroxidase activity that was washed from this root fraction. In contrast, significant side effects occurred in vivo, and substantial peroxidase activity was measured in vitro, from sections 4–6 cm and 18–20 cm behind the seminal root apex. The greatest activity was found with the 4–6 cm section which may be associated with high rates of cell wall lignification. The implications of these results for measurements of root respiration are discussed.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1399-3054.1995.tb06839.x
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