Talk:Auxin

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no mention of regulation of phototropism

Auxins regulate phototropism and there is no clear and specific mention of this in the article. —Preceding unsigned comment added by Kerander (talk • contribs) 03:55, 24 May 2011 (UTC)

Thank You Kerander, thank You for your observation and feedback. I am thankfull for all the feedback I can get, that can help me to see the article through different eyes and help me to improve it.

Phototropism is indeed important concept within auxin topic and generally essential process, which relies entirelly on redistribution of auxin within the stem, leaf stalk or other organs. For auxin, it is actually quite emblematic, because through study of phototropism auxin was actually discovered.

So in sum, it trully belongs to the article.

But my question is, isn't it already there?, It is there on two places already (#here and #here) So that the point You have is rather: that it is there not prominent enough. - As you say - clear and specific mentioning of it. OK, that is what I take.

So in sum, it trully belongs to the article, it is already there, but it might be not that prominent is it ought be.

Well, then let's find where it would fit nicely. The article is already geting long and I try, in order to let it be legible, intelligible and digestible - to keep all examples on rather minimal levels only, ... just enaugh details for ilustrational purposes - to describe importance and nature of auxin. Phototropism is crucial process. But there is really lot of crucial and vital plant processes governed by auxin. (Actually everythink and anythink vital has somethink with auxin in plant body)

I will try to rethink it a bit. But would you mind to help me, if you have an idea? Where do you think, it would fit? To which chapter? And how? Reo ⁺ 20:27, 25 May 2011 (UTC)

No biosynthesis?

There is really no text on auxin biosynthesis? Even slightest mention? HlTo CZ (talk) 15:29, 4 December 2017 (UTC)

New Research

Researchers from Nara Institute of Science and Technology offer new insight into the CRC-mediated auxin homeostasis regulation for proper gynoecium formation! — Preceding unsigned comment added by 2.40.14.214 (talk) 09:21, 4 March 2019 (UTC)

আমি নিতে আগ্রহী 42.0.7.238 (talk) 18:00, 15 April 2025 (UTC)

No reference to other synthetic auxins?

Hello editors,

I would like to propose a set of edits to the “Synthetic auxins” section to improve clarity, completeness, and alignment with standard plant physiology and agronomy sources.

Summary of proposed changes/rationale - Expand the list of representative synthetic auxin herbicides to include additional commonly referenced phenoxy compounds(e.g., mecoprop, dichlorprop, MCPB, 2,4-DB), based on standard references such as the Weed Science Society of America’s Herbicide Handbook.

- Add brief context describing phenoxy herbicides as a broader class of synthetic auxins, including their historical development and typical applications in agriculture (e.g., cereal crops, pasture, turf).

- Clarify that synthetic auxins have a range of uses beyond herbicides, including applications in horticulture and plant propagation (e.g., NAA, IBA).

- Incorporate concise, sourced language on mechanism of action and role in integrated weed management.

Proposed edits to the section “Synthetic Auxins” (suggested new text in bold)

Auxins are toxic to plants in large concentrations; they are most toxic to dicots and less so to monocots.[38] Because of this property, synthetic auxin herbicides, including 2,4-dichlorophenoxyacetic acid (2,4-D), mecoprop (MCPP), dichlorprop (2,4-DP), fenoprop (2,4,5-TP), 2,4-dichlorophenoxybutyric acid (2,4-DB), and 4-(4-chloro-2-methylphenoxy)butyric acid (MCPB), as well as 2,4,5-trichlorophenoxyacetic acid (2,4,5-T), have been developed and used for weed control. These compounds are part of the phenoxy herbicide group, a class of synthetic auxins introduced in the mid-20th century and widely adopted for selective control of broadleaf weeds in cereal crops, pasture, and turf systems. As a group, phenoxy herbicides have been extensively studied in plant physiology and weed science and remain an important component of integrated weed management strategies in many agricultural systems.

(Source: Senseman, S.A. (ed.). (2007). Herbicide Handbook (9th ed.). Weed Science Society of America) 

“Synthetic auxin herbicides (SAHs) mimic the activity of naturally occurring plant hormone indole-3-acetic acid, and they are a commercially important class of herbicides that have historically been used to selectively control dicot weeds” (Source: https://onlinelibrary.wiley.com/doi/abs/10.1002/9781119686699.ch2)

However, some exogenously synthesized auxins, especially 1-naphthaleneacetic acid (NAA) and indole-3-butyric acid (IBA), are also commonly applied to stimulate root growth when taking cuttings of plants or for different agricultural purposes such as the prevention of fruit drop in orchards.

In addition to these compounds, a range of auxin-like substances are routinely used in horticulture and plant propagation to regulate growth processes such as rooting, flowering, and fruit development, reflecting the wide diversity of synthetic auxins used outside of herbicidal applications. (Source: Taiz, L., Zeiger, E., Møller, I. M., & Murphy, A. (2015). Plant Physiology and Development (6th ed.). Sinauer Associates.)

Used in high doses, auxin stimulates the production of ethylene, also a native plant hormone. Excess ethylene can inhibit elongation growth, cause leaves to fall (abscission), and even kill the plant. Some synthetic auxins, such as 2,4-D, mecoprop, dichlorprop, 2,4-DB, MCPB, and related phenoxy herbicides, as well as 2,4,5-T, are marketed also as herbicides. Dicots, such as dandelions, are much more susceptible to auxins than monocots, such as grasses and cereal crops. So these synthetic auxins are valuable as synthetic herbicides. 2,4-D was the first widely used herbicide, and it is still in use.[39] 2,4-D was first commercialized by the Sherwin-Williams company and saw use in the late 1940s. It is easy and inexpensive to manufacture.

Many phenoxy herbicides, including 2,4-D, mecoprop, dichlorprop, and related compounds, remain registered for use in a number of countries, whereas others, such as 2,4,5-T, have been discontinued or are no longer approved in several jurisdictions following regulatory reviews. (Source: U.S. Environmental Protection Agency. Reregistration Eligibility Decision (RED) for 2,4‑D, Office of Pesticide Programs, June 2005.)

Their continued use reflects their effectiveness as selective herbicides and their role in diversified weed control programs that rely on multiple modes of action to manage herbicide resistance. (Source: Senseman, S.A. (ed.). (2007). Herbicide Handbook (9th ed.). Weed Science Society of America)

Triclopyr (3,5,6-TPA), while known as an herbicide, has also been shown to increase the size of fruit in plants. At increased concentrations, the hormone can be lethal. Dosing down to the correct concentration has been shown to alter photosynthetic pathways. This hindrance to the plant causes a response that increases carbohydrate production, leading to larger fruit. Lindsay Thompson 2,4-D Research Task Force (talk) 16:50, 21 May 2026 (UTC)

Proposed edits to the subsection “Herbicide manufacture" section

Hello editors,

I'd like to propose expanding the “Herbicide manufacture” section to include sourced information on formulation (amine vs. ester forms) and environmental fate (e.g., microbial degradation), which are standard elements in agronomy and regulatory literature. Suggested edits are below in bold

Synthetic auxins are used as a kind of herbicide, and high concentrations can disrupt normal plant growth processes, resulting in plant injury.[41]

Synthetic auxins are used as a kind of herbicide and overdosing of auxins will interrupt plants' growth and lead to their death.

Synthetic auxin herbicides are commonly formulated as either amine salts or ester derivatives, which influence properties such as solubility, volatility, and uptake by plant tissues. (Source: Senseman, S.A. (ed.). (2007). Herbicide Handbook (9th ed.). Weed Science Society of America) These formulation approaches are widely used to tailor performance under different environmental and application conditions.

Many phenoxy herbicides have been extensively studied with respect to their environmental fate, and are subject to degradation in soil and water through microbial activity and photochemical processes. (Source: Grossmann, K. (2010). “Auxin herbicides: current status of mechanism and mode of action.” Pest Management Science, 66(2), 113–120. https://doi.org/10.1002/ps.1860) Studies have shown that degradation of phenoxy herbicides such as 2,4-D in surface soils can occur within days under favorable conditions, driven by microbial metabolism and photodecomposition. (Source: Crespin, M. A.; Gallego, M.; Valcárcel, M.; González, J. L. (2001). “Study of the degradation of the herbicides 2,4‑D and MCPA at different depths in contaminated agricultural soil.” Environmental Science & Technology, 35(21), 4265–4270. https://doi.org/10.1021/es0107226)

Microbial biodegradation is recognized as a primary pathway for the breakdown of synthetic auxins in the environment, with diverse soil microorganisms capable of metabolizing these compounds into simpler substances through well-characterized enzymatic pathways. This degradative capacity contributes to their relatively limited persistence under typical field conditions and has been widely documented in environmental and agricultural research. (Source: Senseman, S.A. (ed.). (2007). Herbicide Handbook (9th ed.). Weed Science Society of America)

The defoliant Agent Orange, used extensively by British forces in the Malayan Emergency and American forces in the Vietnam War, was a mix of 2,4-D and 2,4,5-T. The compound 2,4-D is still in use and is thought to be safe, but 2,4,5-T was more or less banned by the U.S. Environmental Protection Agency in 1979. The dioxin TCDD is an unavoidable contaminant produced in the manufacture of 2,4,5-T. As a result of the integral dioxin contamination, the use of 2,4,5-T products has been implicated in leukemia, miscarriages, birth defects, liver damage, and other diseases.

Synthetic auxin herbicides continue to be used in a variety of agricultural and land management applications, where their properties as selective growth regulators are well understood. Ongoing research and regulatory evaluation have further characterized their behavior in different environmental conditions, contributing to their continued role in weed management programs across a range of cropping systems.(Sources: Grossmann, K. (2010). Pest Management Science, 66(2), 113–120., U.S. Environmental Protection Agency. Reregistration Eligibility Decision (RED) for 2,4-D June 2005.)

Lindsay Thompson 2,4-D Research Task Force (talk) 16:51, 21 May 2026 (UTC)