Premium
Causes and location of non‐specific effects of SHAM on O 2 uptake by wheat roots
Author(s) -
Bingham I. J.,
Stevenson E. A.
Publication year - 1995
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.1995.tb06839.x
Subject(s) - peroxidase , salicylhydroxamic acid , chemistry , apex (geometry) , titration , in vivo , in vitro , biochemistry , horticulture , enzyme , botany , biology , inorganic chemistry , microbiology and biotechnology
Uptake of O 2 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 Q all 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 O 2 was titrated with KCN in the presence and absence of SHAM at 1 m M and 25 m M , which yielded Q cy1 values of < 1 and > 1, respectively. The results suggest that at 25 m M , SHAM inhibits the cytochrome pathway, but at 1 m M it stimulates an O 2 ‐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 m M ) and high (25 m M ) 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 m M 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.