Submitted to: Weed Science Society of America Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: December 1, 2003
Publication Date: February 7, 2004
Citation: Hoagland, R.E. 2004. Quinclorac and Quinmeraceffects on pearl millet, hemp sesbania and sicklepod. [Abstract]. Weed Science Society of America. Abstract No. 90. Technical Abstract: Quinclorac (3,7-dichloro-8-quinolinecarboxylic acid) is a pre- or post-emergence herbicide that controls certain grasses and broadleaf weeds. Quinclorac behaves somewhat differently than typical auxenic compounds and its mechanism of action is not completely understood. Studies examined the effects of quinclorac and its analog, quinmerac (7-chloro-3-methyl-8-quinolinecarboxylic acid), using several bioassays on pearl millet (Panicum glaucum L.), hemp sesbania [Sesbania exaltata (Raf.)], and sicklepod (Senna obtusifolia L.). Etiolated plants (4-day old) or seeds were treated with the chemicals (high purity, technical grade), generally at 2.5 mM. Both herbicides slightly inhibited chlorophyll accumulation in greening cotyledons or leaves, and the quinclorac effect was slightly greater than quinmerac. Etiolated shoot cuttings exposed to herbicide solutions, and dark incubation, showed that quinclorac inhibited elongation by 25% (pearl millet) and 27% (hemp sesbania and sicklepod), after 48 h. Quinmerac inhibition of elongation in hemp sesbania and sicklepod equaled that of quinclorac, but quinmerac did not effect pearl millet elongation. Neither compound altered conductivity (electrolyte leakage) in dark-grown cuttings of pearl millet placed in light for 72 h. However, electrolyte leakage in hemp sesbania and sicklepod segments was 15- and 30-fold greater than in untreated tissue, 48 and 72 h after treatment, respectively. Growth inhibition (organ elongation) also occurred when seeds imbibed the herbicide solutions, and were dark-incubated. Both compounds caused a 40% reduction in pearl millet shoots, but quinclorac reduced elongation by 85% in hemp sesbania and sicklepod after 96 h. Quinmerac reduced elongation 75% and 65% in sesbania and sicklepod, respectively. Both chemicals induced club root formation in hemp sesbania and sicklepod. Results indicate differential activity of these herbicides on these species.