Talk:Auxin

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Whoever is working on the Hormonal Activity section, nice job. The idea that Auxin allows the plant to know where it is branching is very interesting. Although it may be current in the literature, it's the first time I have seen it. I haven't been following the lit., but get my information from contributions to places like this. If you want to discuss it with me I'm at socrtwo@s2services.com.

Paul Pruitt

Hello, I apologize, that I was not responding you so long ... lot of work and a bit shy to respond by only laconic way :o), sorry. (Now I want to say something, even if it would be brief at last.)

There are good papers in that area, quite new ones, for example:

• Friml J:Auxin transport - shaping the plant Current Opinion in Plant Biology 2003, 6:7-12

--Good points in what you are interested in.

• Benkova, E. et al. (2003) Local, efflux-dependent auxin gradients as a common module for plant organ formation. Cell 115, 591–602

...

• William D. Teale, Ivan A. Paponov, Franck Ditengou and Klaus Palme (2005) Auxin and the developing root of Arabidopsis thaliana. PHYSIOLOGIA PLANTARUM123: 130–138. 2005

--A litlle bit about roots.

• And one of the newest reviews: Rene´ Benjamins, Nenad Malenica, and Christian Luschnig (2005) Regulating the regulator: the control of auxin transport BioEssays 27:1246–1255,

• (Eric M. Kramer (2004) PIN and AUX/LAX proteins: their role in auxin accumulation. Trends in Plant Science... --From the theoreticall point of view)

There is lot more of them, I don´t remember titles of all of the important ones. There was even something from Friml in Nature, I think...

I don´t know, if you have acces to these journals (as condition for reading), but if you will wish I have them...

My e-mail is open for you: skupa@ueb.cas.cz Reo ^On | +++

Sugar and tropism

Socrtwo, I apologize I had to remove that.

• Phototropism in the shoot and gravitropism in the root may also be explained as Auxin moving away from high concentrations of sugar as in the shoot. For example with phototropism the illuminated side of the shoot makes more sugar and auxin moves away from this to the back shadowed side. In the root, the argument is that the statoliths are made of starch, so once again, when the statoliths pool in the bottom of a cell, this is a high concentration of sugar which auxin moves away from. The tops of the cells therefore have higher concentrations of auxin, widen and the root grows down. (speculative) This does not explain gravitropism is the shoot.

I think, you´re doing some nice and clever suggestions, but still, they remain just only suggestions. However, I am trying, not to be removing them now (but still I´m thinking, it could be misleading for regular reader) and I left them all except one, in this moment on the page (and I´m really looking forward for our future communication about them, if you would). In works above is really detailly described, how it works inside the root. (I mean the transport on cellular level). I apologize that in this moment I will not be detailed myself, but there are several tissue defined streams of auxin. The basic point for all of them are the statoliths. Did you realized, that the main and first stream of auxin is first coming directly towards them? In fact, its going through them. Everything seems to be a bit more complicated (in fact, it is not more complicated, just merely more precisely organized ;o))

Basically I agree with you, that everything has to have its good reason for existence and I do love make suggestions. But now we are in Wikpedia, which is dedicated only to the proven information.... It mean, we could be talking about it personally if you would be interested in it, but we should cautiosly weep out all suggestion from the text.

(I apologize for slovenly english. It is my second one.. I am not native speaker)

Reo ^On | +++ 21:27, 17 December 2005 (UTC)

OK No Problem With the Removal

I agree that this is an Encyclopedeia and the above does not belong since it is unproven. Please feel free, and anybody feel free to remove any of my speculations unless they are labeled as such and prove to be illuminative. Even if they are illuminative it is arguable that some of my speculations are unique and do not belong in this kind of article. I understand that perhaps speculation only belong in Encyclopedia articles if they are widely discussed speculations. Below I include a section that I'm including for all the major hormones, since the effects and localization sections were started by me and need some clarification.--socrtwo 17:47, 18 May 2006 (UTC)

Explanation and Details of "Speculative" Remarks

Hi. I initiated the "Location" and the "Effects" sections. They are derived from 2 1/2 years of library study of all the plant hormones in the mid 1980's! Keep this in mind when looking over the entries. Unfortunately I lost some of my notes and I did some speculation about what the plant is trying to do when it makes a hormone. In the original form of the article, I mixed them up and failed to indicate what was speculative and what was not.

I will try to show below what I remember as being speculations on my part and what is solidly referenced. Please keep in mind that others appear to have added to my list, and some of my speculation could have been right, so some references may actually exist. My aim for revealing this, is in part embarrassment that my entries continue to exist alongside other authoritative articles in Wikipedia and this is not entirely appropriate for an Encyclopedia. Mea culpa. Anyway my speculative article is here: http://www.planthormones.info/.

Locations

• Synthesized in shoot (and root) meristematic tissue - solidly referenced.
• Synthesized in young leaves - solidly referenced.
• Synthesized in mature leaves in very tiny amounts - solidly referenced, the small amount is said to prevent senescence of leaves.
• Synthesized in mature root cells in even smaller amounts - definitely speculative.
• Transported throughout the plant more prominently downward from the shoot apices - this is solidly referenced of course, as to the idea that there is some back-flow of Auxin up the plant, I only vaguely remember this as being found in one article and this may be a false memory.
• Released by meristematic cells when they are in good growing conditions - speculative, although it is kind of a common sense summary of articles I think I read that auxin output decreases with plant stress.
• Released by all cells when they are experiencing conditions that would normally cause a shoot meristematic cell to produce auxin - speculative. The idea here is that all plant cells can behave like shoot cells and can even turn into them, if they experience conditions associated with the shoot experience, that is light, high sugar levels and perhaps both high Oxygen and Carbon Dioxide levels. My logic about the gas level in the shoot has always been fuzzy, since I don't really understand photosynthesis and what goes on in the leaf, although I think it is obvious O2/Co2 ratio should be high in the day and low at night.
• Directly or indirectly induced by high levels of ethylene (speculative) - This is my theory that because of Ethylene's positive feedback phenomenon where a release of little can cause an accelerating ever larger induction of synthesis that the plant may want to induce negative feedback by releasing auxin. This would then prevent the plant from completely senescing itself and would produce hormone cycles with Ethylene and Auxin controlling the output of each other.
• Peaks during the day - this finding comes from one obscure article, that would be great for me to dig up. I believe that it showed that Auxin and Cytokinin peaked during the day and Ethylene and and GA peaked at night, but I do remember the relationship was not perfect, the experiment was done one plant only and the sample size was small. This kind of experiment needs to be redone it a large way.

Effects

• Stimulates cell elongation (if gibberellins are also present, the effect is stronger) - I don't remember the GA part. Someone else might have added that. Definitely Auxin induces cell elongation.
• Stimulates cell division (if cytokinins are also present) - solidly referenced.
• Induces formation and organization of phloem (and xylem) - Mark Jacobs father, William P Jacobs? did a lot of work on this see: http://www.garfield.library.upenn.edu/classics1981/A1981LX51800001.pdf.
• Participates in phototropism, gravitropism, tropism toward moisture and other developmental changes. At least the phototropism and gravitropism are well referenced, the point about other tropisms may have been added by others.
• Induces new root formation by breaking root apical dominance induced by cytokinins - new root formation in undifferentiated calluses of plant cells is well referenced. The breaking of root apical dominance may be speculation. In fact the idea that Cytokinin induces root apical dominance may seem like common sense, but it may too be a speculation.
• Induces shoot apical dominance - This is well referenced.
• Directly stimulates ethylene synthesis (stimulation of ethylene in lateral buds causes inhibition of its growth and potentiation of apical dominance) - this is well referenced. I think the parenthetical observation was added by someone else.
• Inhibits (in low amounts) ethylene formation and transport of precursor - may have been added by someone else. It makes sense though from my speculative theory.
• Inhibits abscission prior to formation of abscission layer (inhibits senescence of leaves) - well referenced n'est ce pas?
• Induces sugar and mineral accumulation at the site of application - I think this is well referenced. I think the actual finding is that it draws all nutrients to point of application including sugar, gases, and other growth hormones like Cytokinin. Thus it is my belief that auxin is an indication that a plant cell, tissue or part is a good bet/investment, that it is producing or harvesting more than enough sugar and gases that are needed for it to grow and for any cell dependent on it for sugar and gases (e.g. - root cells are dependent on shoot cell for their sugar and gases).
• Stimulates Flower initiation - did someone else put this in? What I remembered about flower in fruit initiation was that whether a particular hormone induced it was species dependent and differed from species to species, although from theory a high enough level of auxin could indicate to the plant that enough supportive sugar and gases was around to produce the non-photosynthesizing flowers.
• Is sex determinator - I remember reading about this, but it was a confusing discussion and seem to differ from plant to plant.
• Inhibits root hair growth and causes them to die back (speculative) - Huh? from theory I think the more proper hormone for this would be cytokinin, since high levels of it would be an indication that the root is prospering when it comes to minerals and water and does not need to risk opening up more surface are with root hairs as root hairs may be an entry point for infection or other stresses.
• Stimulates the rate of metabolism of cells in the root, thus increasing their efficiency of water and mineral uptake(speculative) - the idea here would be to try to compliment the growth allowing levels of sugar and gases that Auxin is an indication of.
• Indicates when cells have more than enough sugar and gases available than are needed for existence at their present size. It is a shoot health indicator and growth signal, and one of its essential missions is to compliment the excess sugar and gases with an excess of root-derived water and minerals. It therefore induces new roots. If Cytokinin is present, this is an indication that the root is healthy and the plant is completely ready to grow. In this case, it simply cooperates with cytokinin to cause cell division and balanced plant growth. (speculative)
• Appears in general to be induced at the site of high concentrations of sugar, but always moving in a direction away from this synthesis. Since Auxin attracts nutrients to the cell where it is, this transport of auxin away from sugar synthesis may partly explain the transport of sugar in the phloem to the roots. The sugar may just be following the auxin. (speculative)--socrtwo 17:47, 18 May 2006 (UTC)

Chemical Nature

Is Auxin nitrogenous or non-nitrogenous?TathD 14:27, 4 February 2007 (UTC)

my ques is to ask how to start growing a plant in delhi for showing effects of auxins or how to prepare a simple project over auxin

Fruit Growth

It seems to need a bit more information, as well as citations. I've been looking through some articles myself but I'm having trouble finding out if additional auxin causes parthenocarpy or if it represses it. --Deepraine (talk) 02:02, 9 December 2007 (UTC)

Don't know enough to help myself, but very glad to see you here. When you get done with this (:-)), there's lots more to work on (for example, see Wikipedia:WikiProject Plant Evo Devo). Kingdon (talk) 04:23, 9 December 2007 (UTC)

Proposed merge of Polar auxin transport

I see there are merge tags for Polar auxin transport to be merged into this article (Auxin). My first reaction is that the former is too specialized, and Auxin, instead of trying to explain the molecular basis of how auxin is transported, should just link to the transport article(s) and perhaps summarize them (for example, the Auxin article now contains "Transported throughout the plant . . ." and somewhere in this area might be a good place for a link). But I'd gladly defer if those with more knowledge have another opinion. Kingdon (talk) 16:45, 11 December 2007 (UTC)

Keep separate I see the concept of Polar auxin transport (PAT) as one of the most important concepts in plant development and plant's physiology. Only the state/extent of the current article about PAT might trigger some doubts whether it is desirable. Nevertheless it is truth that the main article auxin should cover some basic ideas about its transport - in to some extent. This transport is absolutely unique phenomenon in plant and probably in all living kingdoms and it is focus of long lasting research. The interest of plant science researchers in this area is relatively measurably very high and conclusions from it are directly applicable (and applied) in Horticulture and for the growth of the in vitro plants. I support the division in two articles.

I was planing that I will personally help the article and cover the area (I contribute to research in the area) but I do not promise it any more, for it is very hard to find the time for appropriate wording there. The science simply takes its bill. :). But I will try.

Summary: 1) PAT is important topic 2) Often intensively lectured in specialized classes (Horticulture, plant sciences) 3) Quite complicated to cover and while having thousands of scientific articles as an background - possibly extensible in full length, full detailed article. 4) Auxin article may cover general idea about the substance and be more balanced even without PAT possibly topic for long article. One or two introductory paragraphs about PAT in it should be proper approach. Reo ^ON | +++ 18:02, 17 December 2007 (UTC)

Agree with this. PAT brings together many different aspects of auxin. pH inside and out cell, ATPases, PIN proteins and none of these aspects would warrant a large section in the Auxin article itself. David D. (Talk) 18:12, 17 December 2007 (UTC)

OK, I've removed the merge tags. I now see that the Auxin article already had one link to polar auxin transport, so I didn't try to change anything. Kingdon (talk) 21:10, 17 December 2007 (UTC)

Image for the Lead section

Native auxins

indole-3-acetic acid (IAA) is the most abundant and the basic auxin natively occuring and functioning in plants.

There are three more native - endogenous auxins:

4-chloroindole-3-acetic acid (4-CI-IAA)

2-phenylacetic acid (PAA)

Indole-3-butyric acid (IBA)

I believe that new setting for the Lead image is needed. At the same time the galleries of auxinic compounds are not well fitting either.

I am trying to rething new approaches and this seems to be one promising. To group the native auxins in compound image bellow leading section.

I will still need to prepare it beter.

For now I leave it prepared here :)

Well maybe If I could do it somehow IAA on left and the small other three in column on the right from IAA would be best :) --Reo ⁺ 00:35, 20 May 2011 (UTC)