Chlormequat_chloride

Chlormequat

Chlormequat

Chemical compound

Chlormequat is an organic compound with the formula ClCH
2CH
2N(CH
3)+
3 that is used as a plant growth regulator. It is typically sold as the chloride salt, chlormequat chloride[1] (C5H13Cl2N), a colorless hygroscopic crystalline substance that is soluble in water and ethanol.[2] It is an alkylating agent and a quaternary ammonium salt. Chlormequat is one of the onium-type growth regulators.[3]

Quick Facts Names, Identifiers ...

Plant interactions

Chlormequat was discovered in the 1950s, and was the first known plant growth regulator. It can cause stem thickening, reduced stem height, additional root development, plant dwarfing, and increase chlorophyll concentration.[4]

Chlormequat is an inhibitor of gibberellin biosynthesis, thereby causing reduced cell elongation and thicker sturdier stalks that facilitate harvesting of cereal crops.[5] It can also be used as an adjuvant for herbicides by retarding their oxidative disposal by plants. This is due to cytochrome P450-inhibition.[3][2]

Regulation and toxicity

In the United States, chlormequat is classified as a low risk plant growth regulator and it is registered for use on ornamental plants grown in greenhouses, nurseries, and shadehouses.[6] The LD50 (rat, oral) is approximately 670 mg/kg.[2] Exposure to high levels of chlormequat has been linked to developmental toxicity in animal models.[7][8]

Chlormequat has not previously been registered for use on food crops in the United States. In April 2023, the U.S. Environmental Protection Agency proposed allowing the use of the chemical on food crops such as barley, oat, triticale, and wheat. The EPA’s human health risk assessment indicated "no dietary, residential, or aggregate (i.e., combined dietary and residential exposures) risks of concern." No risks were identified by EPA to aquatic species of invertebrates, vertebrates, and plants in addition to terrestrial plants.[9]

EU Regulations

In July 2022, the EU published Regulation (EU) 2022/1290, which amended the maximum residue levels (MRLs) for chlormequat in or on certain products, based on the scientific assessment of EFSA and the international standards of the Codex Alimentarius Commission. The regulation lowered the MRL for chlormequat in citrus fruits from 2 mg/kg to 0.5 mg/kg, and also modified the MRLs for other products such as apples, pears, quinces, cherries, plums, apricots, and barley. The regulation also set a specific MRL of 0.01 mg/kg for Spodoptera exigua multicapsid nucleopolyhedrovirus (SeMNPV) isolate BV-0004, a biological plant protection product containing chlormequat as a co-formulant. The regulation entered into force on 14 August 2022.[10]

References

  1. [1]
    "Chlormequat chloride". ChemSpider. Archived from the original on 13 May 2023. Retrieved 18 February 2024.
  2. [2]
    Wilhelm Rademacher, Lutz Brahm "Plant Growth Regulators" in Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim, 2010. doi:10.1002/14356007.a20_415.pub2
  3. [3]
    Rademacher, Wilhelm (2000). "Growth Retardants: Effects on Gibberellin Biosynthesis and Other Metabolic Pathways". Annual Review of Plant Physiology and Plant Molecular Biology. 51 (1). Annual Reviews: 501–531. doi:10.1146/annurev.arplant.51.1.501. ISSN 1040-2519. PMID 15012200.
  4. [4]
    Katel, Shambhu; Mandal, Honey Raj; Kattel, Sujata; Yadav, Shubh Pravat Singh; Lamshal, Baibhav Sharma (December 2022). "Impacts of plant growth regulators in strawberry plant: A review". Heliyon. 8 (12): e11959. doi:10.1016/j.heliyon.2022.e11959. PMC 9712129. PMID 36466575.
  5. [5]
    Gowariker, Vasant; Kalyani Paranjape; Sudha Gowariker; V. N. Krishnamurthy (2013). The pesticide encyclopedia. Wallingford: CABI. p. 93. ISBN 978-1780640143.
  6. [6]
    "72 FR 67296 - Chlormequat Chloride Reregistration Eligibility Decision for Low Risk Pesticide; Notice of Availability". GovInfo. Archived from the original on 26 May 2022. Retrieved 18 February 2024.
  7. [7]
    "Chlormequat". Food and Agricultural Organization of the United Nations.
  8. [8]
    Wang, X; Weidong, H (November 2023). "Reproductive and developmental toxicity of plant growth regulators in humans and animals". Pesticide Biochemistry and Physiology. 196: 129–33. doi:10.1016/j.pestbp.2023.105640. PMID 37945238.
  9. [9]
    "EPA Proposes to Register New Uses of Pesticide Chlormequat Chloride". www.epa.gov. 2024-04-26. Retrieved 2024-02-16. Before issuing this proposed registration decision, EPA assessed whether exposures to this product would cause unreasonable adverse effects to human health and the environment, as required by the Federal Insecticide, Rodenticide, and Fungicide Act (FIFRA). Based on EPA's human health risk assessment, there are no dietary, residential, or aggregate (i.e., combined dietary and residential exposures) risks of concern. EPA's ecological risk assessment identified no risks of concern to non-target, non-listed aquatic vertebrates that are listed under the Endangered Species Act, aquatic invertebrates, and aquatic and terrestrial plants.
  10. [10]
    "Regulation - 2022/1290 - EN - EUR-Lex". eur-lex.europa.eu. Retrieved 2024-02-25.
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