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Charles S Buer buer at WPI.EDU
Fri May 3 04:34:29 EST 1996

Two things:

1.  Roundup and 2,4-D are two different things.  Roundup is glyphosate, an
herbicide which will kill both monocots and dicots.  2,4-D is a broadleaf
weed killer, commonly used for dandelions (one commercial name I have seen
is Weed-B-Gon).  2,4-D is also used as an artificial plant auxin. In very
small doses it will induce callus growth in combination with a cytokinin. 
2,4-D will affect monocots if applied in high enough doses.  Current
hypothesis of action is that 2,4-D alters DNA transcription and RNA
translation and plants lose coordinated growth because enzymes needed are
not produced correctly.

2.  Glyphosate breaks down rapidly (it blocks formation of an enzyme
called EPSP synthase in the shikimic acid pathway), but the same isn't
true for the chloride compounds.  One of their breakdown products is
dioxin which is very persistant and toxic (especially in the case of
2,4,5-T which is banned). 

Personally, I'd rather have the dandelions which would have a tougher time
growing if folks would mow their grass longer.

Charles S. Buer                         |
Biology/Biotechnology Dept.             |email:  buer at wpi.wpi.edu
Worcester Polytechnic Institute         |Phone:  (508) 831-5052
100 Institute Rd.                       |FAX:  (508) 831-5936
Worcester, MA 01609                     |

On Thu, 2 May 1996, Julie J. Gold wrote:

> Hi.
> I am new to newsgroups, and am attempting to respond to a note which I read 
> about the herbicide 2,4-d (commercially common as Roundup). The compound is 
> one of a class of phenoxychlorides (I probably am not remembering the absolute 
> correct spelling, and my books are unavailable, so forgive me please). These 
> molecules are essentially phenol rings connected by oxygen atoms, with 
> chloride radicals on the rings. They are very reactive. In plants, as pointed 
> out, they act much as growth hormone auxin, and in effect the plant grows 
> itself to death. Hence, the gnarled leaves which form on treated plants. I 
> believe that at least one effect of the compound is to interfere with the 
> photosynthetically driven electron transport chain. 
> These herbicides were commonly used in forestry applications, a notorious 
> example being 2,4,5-t, Agent Orange used in Vietnam, and a molecule related to 
> 2,4-d. The numbers refer to the positions of chloride around the rings. An 
> unfortunate side-effect in forestry applications is the destruction of stream 
> life. It is true the compounds have a fairly rapid breakdown in soil (because 
> they are reactive!), but I certainly look for alternate control measures. I 
> find the smell of the stuff repugnant, especially on a lovely afternoon 
> pedalling my way home past a sea of chemically treated sod. 
> Personally, I don't trust data relative to the safety of 2,4-d. But 
> professionally I suppose I must reserve judgement. At least treat the stuff 
> respectfully if you need to use it, reading ALL SAFETY PRECAUTIONS, and 
> following proper disposal methods.
> Thanks for listening to a "newbie",
> (Dr.) Julie Gold
> Winnipeg, MB

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