E. Hewitt, B. Notton
Dec 1, 1966
Citations
0
Influential Citations
12
Citations
Journal
The Biochemical journal
Abstract
Substituted uracil derivatives including 5-bromo3-sec.-butyl-6-methyluracil (bromacil) and 5-bromo3-isopropyl-6-methyluracil (isocil) were found by Bucha, Cupery, Harrod, Loux & Ellis (1962) to possess severe phytotoxic properties, resembling those of other herbicides found to inhibit photosynthesis in independent experiments by Hoffinan, MeGahen & Sweetster (1964) and by Hilton, Monaco, Moreland & Gentner (1964). The compounds were effective at about micromolar concentrations with chloroplasts from several sources. Following the work of Hewitt & Afridi (1959) and Afridi & Hewitt (1962, 1965), who tested effects of several potential antimetabolites on the induction of nitrate reductase in excised plant tissues when nitrate or molybdenum was present as inducer, similar experiments with the substituted uracils revealed unexpectedly large effects on enzyme production. Methods. The methods used to demonstrate the formation of nitrate reductase in excised tissues from plants grown in sand cultures, together with reports of the effects of time, temperature and concentration of inducers and inhibitors on the activities produced, were fully described by Afridi & Hewitt (1964, 1965). In the present work induction by nitrate was carried out with leaf tissues from plants deprived of nitrate for about 5 days until endogenous enzyme activity had decayed to low levels (Afridi & Hewitt, 1964), and induction by molybdenum was tested on tissues from plants grown with nitrate in molybdenumdeficient culture media (Hewitt, 1966). Solutions of sodium nitrate (4mM) or sodium molybdate (3,UM) alone or with the inhibitors were vacuum-infiltrated into well-mixed 1g. samples of small fragments of tissues ofcauliflower (Brassica oleracea var. botryti8)