Some years ago, we investigated a variety of different agars
(some of which you mention). We found reproducible differences in
root elongation rate but perhaps on the order of 10 to 20 %. Clearly
the roots liked some agar better than others. We also found a little
bit later when using phytagel that root elongation rate depended on
the temperature the molten mix was held at before pouring, or might
have simply been quite irreproducible. But again I am talking about
differences on the order of 20%. Big enough to readily measure but
not monstrous. On no agar did we see the kind of developmental change
you are mentioning. On some conditions I have seen (and read) that
severely salt stressed or water deficit stressed roots will swell so
I'd guess what you are describing goes way beyond what can be
expected from different brands/formulations of agar.
Hope this helps,
At 3:10 PM -0600 2/9/08, Falbel, Tanya G. wrote:
>>Over the years, I've used several brands of agar for growing
>Arabidopsis seedlings on MS medium,
>from Gibco, Sigma, and others. I've heard that some groups use Noble agar,
>others, bacto-agar, others in the past have washed their own agar,
>used phytagel or other
>gelling agents. I have two questions:
>>1) What brands of agar are most commonly in use now by groups? I've
>found something similar
>to Gibco's Phytagar that is now available through Caisson labs.
>Other groups seem to like Sigma's
>A1296. But besides those, what do most groups use? I'm especially
>interested in the opinion of
>groups that measure root length or root branching - growing roots
>vertically on plates
>for more than just a couple of days. (as opposed to just antibiotic selection)
>>2) Does anyone know what inhibitors are washed away? Are
>micronutrient ions or other toxic
>compounds bound to the crude agar? Has anyone looked into this?
>This may have been a question
>that came up among researchers 10 years ago, but I couldn't find any
>record in the archives.
>>Here's why I'm asking. I made up a batch of medium with a brand of
>'purified agar for microbial use',
>and got a very strong inhibition of root meristems. Seed
>germination was good, but roots failed to elongate
>any further after about 4 days of growth. The root meristems became
>a swollen mess, reminiscent of what
>happens in weak gnom alleles. I'm trying to decide if this is
>something worth looking into.
>>I know that for regeneration of plants in tissue culture, folks are
>very fussy about particular brands of agar.
>>Please let me know what brands you have used with success or failure.
>I'd be especially interested in other similar experiences - where a brand
>wreaked havoc on root meristems.
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