Pea (Pisum sativum) seed production as an assay for reproductive effects due to herbicides

Abstract

Even though herbicide drift can affect plant reproduction, current plant testing protocols emphasize effects on vegetative growth. In this study, we determined whether a short-growing season plant can indicate potential effects of herbicides on seed production. Pea (Pisum sativum cv. Dakota) plants were grown in mineral soil in pots under greenhouse conditions. Plants were treated with a variety of herbicides (dicamba, clopyralid, glufosinate, glyphosate, 2-methyl-4-chlorophenoxyacetic acid, primisulfuron, or sulfometuron) at below standard field application rates applied at a vegetative stage of growth (approximately 14 d after emergence) or at flowering (approximately 20 d after emergence). Pea seed production was greatly reduced by sulfometuron at the minimum concentration used (0.001 x field application rate), with an effective concentration producing a 25% reduction in seed dry weight of 0.00007 x field application rate. Primisulfuron and glyphosate had a 25% reduction in seed dry weight for seed dry weight of 0.0035 and 0.0096 x field application rate, respectively. Clopyralid and dicamba reduced pea seed dry weight at a 25% reduction in seed dry weight of approximately 0.07 x field application rate. Glufosinate only reduced pea seed weight in one experiment, with a 25% reduction in seed dry weight of 0.07 and 0.008 x field application rate at vegetative growth and flowering stages, respectively. Pea seed dry weight was not affected by 2-methyl-4-chlorophenoxyacetic acid. Plant developmental stage had no consistent effect on herbicide responses. Reduced seed production occurred with some herbicides (especially acetolactate synthase inhibitors), which caused little or no reduction in plant height or shoot biomass and little visible injury. Thus, pea may be a model species to indicate seed reproductive responses to herbicides, with seed production obtained by extending plant growth for usually only 7 d longer than the period usually used in the vegetative vigor test.

Phytotoxicity assay for seed production using Brassica rapa L.

“…Five herbicides were tested in these studies. Three were acetolactate synthase (ALS)‐inhibiting herbicides that reduced seed production based on controlled experiments (Fletcher et al 1993, 1996; Boutin et al 2000; Kjær et al 2006; Olszyk et al 2009). Two of these were from the sulfonylurea chemical family, sulfometuron (Oust®, sulfometuron methyl, 2‐[[[[(4,6‐dimethyl‐2‐pyrimidinyl)amino]carbonyl]amino] sulfonyl]benzoic acid, E.I.…”

“…The EPA, ASTM, and OECD plant toxicity tests focus on vegetative growth responses, i.e., canopy height and shoot dry weight; however, research suggests that plant reproduction can be decreased with less effect on vegetative growth or injury to plants (Olszyk et al 2009, 2010; Pfleeger et al 2008; Fletcher et al 1993, 1995, 1996). Low‐dose, high‐potency herbicides are of particular concern, especially those that inhibit the enzyme acetolactate synthase (ALS) (Fairbrother and Kapustka 2001), e.g., sulfonylureas, imidazolinones, and triazolopyrimidines (Mallory‐Smith and Retzinger 2003).…”

Comparing effects of low levels of herbicides on greenhouse- and field-grown potatoes (Solanum tuberosum L.), soybeans (Glycine max L.), and peas (Pisum sativum L.)

“…Chem. 30,2011were an artifact of the experimental design, because plants were measured 14 d after exposure, with exposures occurring at different growth stages, i.e., tuber initiation versus tuber bulking (data not shown). The other measures were taken at the end of the experiment.…”

“…Growth of peas outside under conditions with higher peak temperatures resulted in plants becoming stressed and, consequently, performing poorly in terms of seed production. Peas seem particularly well suited for controlled environmental conditions and this quality, along with their short life cycle, makes peas a candidate species for a reproductive test [15,30].…”

Potato (Solanum tuberosum) greenhouse tuber production as an assay for asexual reproduction effects from herbicides

“…However, use of vegetative seedlings may not correspond to reproductive responses, as shown by recent research with peas, which indicated that plant reproduction (seed production) was decreased, with less effect on vegetative growth or injury to plants [2]. Low-dose, high-potency herbicides are of particular concern, especially inhibitors of the enzyme acetolactate synthase (ALS) such as sulfonylureas and imidazolinones [3].…”