Soybean Mitochondrial Response to Prometryne and Fluometuron

Abstract

Experiments were conducted to determine the effect of 3-(m-trifluoromethylphenyl)-1,1-dimethylurea (fluometuron) and 2,4-bis(isopropylamino)-6-methylmercapto-s-triazine (prometryne) on oxygen consumption by mitochondria isolated from the hypocotyls of soybean (Glycine max L., var. Lee) seedlings. Prometryne caused a decrease in second state 3 oxidation of both malate and succinate, but the decrease was overcome by 2,4-dinitrophenol (hereinafter referred to as DNP), indicating a response similar to that of oligomycin. Fluometuron caused an increase in second state 4 oxidation of both malate and succinate and overcame the inhibition of oxidative phosphorylation caused by oligomycin, indicating an uncoupling response similar to DNP. Fluometuron was also shown to reverse the inhibition of oxidative phosphorylation caused by prometryne. Concentrations of prometryne causing the 50% inhibitory response were somewhat higher than those reported for s-triazines on other tissues, while those for fluometuron were well within the inhibitory range reported for other substituted ureas.

Determination and Characterization of the Effects of Fluometuron and MSMA onChlorella

“…Vmax for this plot was 133%. With observed values over 100%, the level of one-half Vmax can be assumed to be 50% (10). The corresponding herbicide level (Km) was found to be 2.6 x 10-6 M, a figure close to that obtained from the probit plot.…”

“…Gramlich and Frans (4) found that NAA (naphthaleneacetic acid) and 2,4-D produced growth inhibition of Cblorella pyrenoidosa consistent with this hypothesis, although the activity of atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino )-s-triazine) could not be so characterized. Similarly, McDaniel and Frans (10) found that probit analysis more satisfactorily characterized the activity of fluometuron and prometryn [2,4-bis(isopropylamino)-6-(methylthio)-s-triazine ] on cotton and soybean seedling inhibition.…”

“…The 50% inhibition concen- herbicide on systems affecting cell number vs systems affecting chlorophyll synthesis. McDaniel and Frans (10) reported that fluometuron action on soybean, measured as inhibition of fresh weight, was satisfactorily characterized by probit but not by kinetic analysis. Fluometuron effect on cotton fresh weight was also characterized by probit analysis, but yielded a bidirectional response line, similar to those lines obtained here for chlorophyll content and oxygen evolution.…”

The Effect of Reaction Media on the Coupling and Uncoupling of Respiration in Corn Mitochondria

“…Differences observed in the reactions of mitochondria from the same, or different, plant species are on occasion accounted for in the differences of the experimental media. The osmoticant used generally varies between sucrose (Hackett 1961, Lotlikar and Remmert 1968, and Baddeley and Hanson 1967, mannitol (McDaniel andFrans 1969, Ikuma andBonner 1967), or a potassium salt (either chloride or acetate) (Lorimer andMiller 1969, Stoner and. Typically, in studies of corn mitochondria we have employed a reaction media of 200 mM KCl, 20 mM Tris-HCl (pH 7.5), and 1 mg/ml BSA.…”

“…Most often it is hypothesized that an uncoupler is acting to break down the non-phosphorylated high energy intermediates of the Chance and Williams (1956) terminology. Concomitant to the uncoupling phenomena with an uncoupler such as 2,4-dinitrophenol (DNP) is a stimulation of state 4 oxidation (McDaniel and Frans 1969).…”