Physiological responses of glyphosate-resistant and glyphosate-sensitive soybean to aminomethylphosphonic acid, a metabolite of glyphosate

• Published in: Chemosphere (Oxford) Vol. 83; no. 4; pp. 593 - 598
• Main Authors: Ding, Wei, Reddy, Krishna N., Zablotowicz, Robert M., Bellaloui, Nacer, Arnold Bruns, H.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.04.2011; Elsevier
• Subjects: acids; Aminomethylphosphonic acid; AMPA; Animal, plant and microbial ecology; Applied ecology; Biological and medical sciences; chlorophyll; Chlorophyll - metabolism; Chlorophylls; Conductance; Drug Resistance - genetics; Ecotoxicology, biological effects of pollution; foliar application; Fundamental and applied biological sciences. Psychology; General aspects; Glycine - analogs & derivatives; Glycine - toxicity; Glycine max; Glycine max - drug effects; Glycine max - genetics; Glycine max - physiology; Glyphosate; greenhouses; Herbicides - toxicity; Injuries; Isoxazoles; leaves; mechanism of action; nitrate reductase; Nitrates; nitrogen content; Nitrogen fixation; nodulation; Organophosphonates - toxicity; Photosynthesis; Photosynthesis - drug effects; physiological response; plant damage; plant growth; Plants, Genetically Modified; Reductases; roots; shoots; Soybean injury; Soybeans; stomatal conductance; Tetrazoles; Transpiration; water vapor; Yellowing; Nitrogen fixation; Aminomethylphosphonic acid; AMPA; Soybean injury; Photosynthesis; Glyphosate; Metabolite; Glycine max; Leguminosae; Dicotyledones; Angiospermae; Spermatophyta; Degradation product
• ISSN: 0045-6535; 1879-1298
• DOI: 10.1016/j.chemosphere.2010.12.008

► Aminomethylphosphonic acid (AMPA) is formed in soybean and is known to cause yellowing in soybean. ► AMPA reduced chlorophyll content, photosynthesis, and root respiration in soybean. ► AMPA had no effect on nodulation, nitrogenase activity, plant height, shoot dry weight in soybean. ► AMPA’s mode of action is different from that of glyphosate. ► AMPA may be involved in chlorophyll biosynthesis. Aminomethylphosphonic acid (AMPA) is formed in glyphosate-treated glyphosate-resistant (GR) and glyphosate-sensitive (GS) soybean [ Glycine max (L.) Merr.] plants and is known to cause yellowing in soybean. Although, AMPA is less phytotoxic than glyphosate, its mode of action is different from that of glyphosate and is still unknown. Greenhouse studies were conducted at Stoneville, MS to determine the effects of AMPA on plant growth, chlorophyll content, photosynthesis, nodulation, nitrogenase activity, nitrate reductase activity, and shoot nitrogen content in GR and GS soybeans. AMPA was applied to one- to two-trifoliolate leaf stage soybeans at 0.1 and 1.0 kg ha −1, representing a scenario of 10% and 100% degradation of glyphosate (1.0 kg ae ha −1 use rate) to AMPA, respectively. Overall, AMPA effects were more pronounced at 1.0 kg ha −1 than at 0.1 kg ha −1 rate. Visual plant injury (18–27%) was observed on young leaves within 3 d after treatment (DAT) with AMPA at the higher rate regardless of soybean type. AMPA injury peaked to 46–49% at 14 DAT and decreased to 17–18% by 28 DAT, in both soybean types. AMPA reduced the chlorophyll content by 37%, 48%, 66%, and 23% in GR soybean, and 17%, 48%, 57%, and 22% in GS soybean at 3, 7, 14, and 28 DAT, respectively. AMPA reduced the photosynthesis rate by 65%, 85%, and 77% in GR soybean and 59%, 88%, and 69% in GS soybean at 3, 7, and 14 DAT, respectively, compared to non-treated plants. Similarly, AMPA reduced stomatal conductance to water vapor and transpiration rates at 3, 7, and 14 DAT compared to non-treated plants in both soybean types. Photosynthesis rate, stomatal conductance, and transpiration rate recovered to the levels of non-treated plants by 28 DAT. Plant height and shoot dry weight at 28 DAT; nodulation, nitrogenase activity at 10 DAT, and nitrate reductase activity at 3 and 14 DAT were unaffected by AMPA. AMPA reduced root respiration and shoot nitrogen content at 10 DAT. These results suggest that a foliar application of AMPA could indirectly reduce photosynthesis through decreased chlorophyll content in GR and GS soybean up to 14 DAT, but affected plants can recover to normal growth by 28 DAT.