Triaziflam and Diaminotriazine Derivatives Affect Enantioselectively Multiple Herbicide Target Sites

Abstract

Diaminotriazines, Cellulose Synthesis, Mitotic Disrupter Herbicides, Photosynthetic Electron Transport InhibitorsEnantiomers of triaziflam and structurally related diaminotriazines were synthesized and their herbicidal mode o f action was investigated. The compounds caused light and darkdependent effects in multiple test systems including heterotrophic cleaver and photoautotrophic algal cell suspensions, the Hill reaction o f isolated thylakoids and germinating cress seeds. Dose-response experim ents revealed that the fSj-enantiomers of the compounds pref erentially inhibited photosystem II electron transport (PET) and algae growth with efficacies similar to that of the herbicide atrazine. In contrast, the (R )-enantiomers of the diaminotri azines were up to 100 times more potent inhibitors of growth in cleaver cell suspensions and cress seedlings in the dark than the (S)-enantiomers. The most active compound, the (R)-enantiomer of triaziflam, inhibited shoot and root elongation of cress and maize seedlings at concentrations below 1 (j.m. The meristematic root tips swelled into a club shape which is typical for the action of mitotic disrupter herbicides and cellulose biosynthesis inhibitors. Microscopic examination using histochemical techniques revealed that triaziflam (7?)-enantiomer blocks cell division in maize root tips 4 h after treatment. The chromosomes pro ceeded to a condensed state of prometaphase but were unable to progress further in the mitotic cycle. Disruption of mitosis was accompanied by a loss o f spindle and phragmoplast micotubule arrays. Concomitantly, cortical microtubules decreased which could lead to isodiametric cell growth and consequently to root swelling. In addition, a decline in cellulose deposition in cell walls was found 24 h after treatment. Compared to the (7?)-form, triaziflam (S)-enantiomer was clearly less active. The results suggest that triaziflam and related di aminotriazines affect enantioselectively multiple sites o f action which include PET inhibitory activity, mitotic disruption by inhibiting microtubule formation and inhibition of cellulose synthesis.

Glyphosate, Alachor and Maleic Hydrazide have Genotoxic Effect on Trigonella foenum-graecum L.

“…All the three active ingredients exhibited significant inhibitory action on mitosis in root tips germinated from fenugreek seeds. The effect on mitosis could be due to their inhibitory action on synthesis of DNA, RNA and proteins Barriuso et al 2010;Kaymak 2005;Mike et al 1983;Egli et al 1985) and/or spindle fibers (Barbara et al 1991;Grossmann et al 2001;Claudio et al 1992). In addition, Glyphosate is known to block the cell cycle in G2-M phase by inhibiting the CDK1/cyclin activation (Marc et al 2002(Marc et al , 2004a.…”

“…These results indicate the potential of these agents to induce mitotic irregularities, as observed by few earlier studies (Abdelsalam et al 1997;Siddiqui et al 2009). The chromosomal aberration induced by these herbicides could be due to their inhibitory action on spindle proteins and also their ability to induce sister chromatid exchange (Barbara et al 1991;Grossmann et al 2001;Claudio et al 1992;Tartar et al 2006;Gichner et al 2002).…”

What it takes to get a herbicide's mode of action. Physionomics, a classical approach in a new complexion

“…For the determination of effects on the Hill reaction, thylakoids were isolated from shoots of young plants of Triticum aestivum L and assay was performed as described by Grossmann et al 12 Isolated thylakoids were suspended in the reaction medium (0.75 ml) which contained sucrose (0.1 M ), tricine‐NaOH (pH 8.0; 50 m M ), magnesium chloride (5 m M ) and chlorophyll (41 µg ml −1 ). The influence of the compounds on photosynthetic electron transport in photosystem II was evaluated according to the method of Avron and Shavit 13.…”

Weed Control, 2. Individual Herbicides

“…Triaziflam Triaziflam can be synthesized by reaction of 6-(1-fluoro-1-methyllethyl)-1,3,5-triazine-2,4-diamine with 3,5-dimethyl-(2-chloro)isopropylphenolate [145].…”