how r weedicides weed specific??

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rosalin
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how r weedicides weed specific??

Post by rosalin » Thu Feb 01, 2007 10:51 am

i read sumwhre that synthetic auxins such as 2,4- Dichlorophenoxyacetic acid (or 2,4-D) are often used as weedicides (because auxins in excess stimulate the production of ethylene which causes leaf fall and the plant begins to die).

how is it that they only affect the weeds and not the crop? :?

(is it because weeds have high growth rate? :shock: )
Last edited by rosalin on Fri Feb 02, 2007 10:21 am, edited 1 time in total.
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Post by SororSaudade » Thu Feb 01, 2007 11:45 am

maybe, as weeds are smaller, they are easily afected by smaller amounts of those auxins (though i'm not sure).

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Post by rosalin » Thu Feb 01, 2007 5:27 pm

what ? i don't understand. i was thinking 'bout the HIGH growth rate of weeds that would lead to a higher conc. of growth hormones like auxins as compared to the crop.
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Post by SororSaudade » Thu Feb 01, 2007 6:08 pm

well, I can't understand your point either :P

I've never heard of auxins as "weedicides", but what I ment is that smaller plants could be less tolerant to certain amounts of auxins, but yet this may be a stupid answer, I don't know.

If you find the right answer please let me know :)

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Post by sachin » Thu Feb 01, 2007 6:13 pm

weedicides are made according to weed's physiology so that it will harm the weekest point of weed's physiology which is strenght of our important plant's physiology...
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Post by rosalin » Fri Feb 02, 2007 10:02 am

SororSaudade wrote:I've never heard of auxins as "weedicides", but what I ment is that smaller plants could be less tolerant to certain amounts of auxins, but yet this may be a stupid answer, I don't know.


ah! i see ur point now :idea: but i'm not so sure.
i'm trying to find out.

sachin wrote:so that it will harm the weekest point of weed's physiology which is strenght of our important plant's physiology...


could u please elaborate? :)
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Post by mith » Fri Feb 02, 2007 3:31 pm

High growth rate...so if it's sped up I'm guessing it ages faster...
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Post by rosalin » Sat Feb 03, 2007 4:45 pm

i found something in wikipedia 'bot this:

wikipedia.com wrote: Some synthetic auxins such as 2,4-D and 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) can be used as herbicides.Broad-leaf plants (dicots) such as dandelions are much more susceptible to auxins than narrow-leaf plants (monocots) like grass and cereal crops.


http://en.wikipedia.org/wiki/Auxin

i guess this more or less clarifies things a bit.
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Post by MrMistery » Sat Feb 03, 2007 8:23 pm

the clarification is: monocots are much better at rapidly inactivating excess auxins than eudicots. Since crop plants are monocots, they can resist the auxins while weeds(mostly eudicots) die from excess hormones. Nothing to do with growth rates really..
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Post by SororSaudade » Sun Feb 04, 2007 9:10 pm

nice to know that :)

Thanks for sharing the right answer!

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