[Arabidopsis] brands of agar

Grant Cramer via arab-gen%40net.bio.net (by cramer from unr.edu)
Tue Feb 12 19:40:19 EST 2008


I have found very negative effects on root growth using BactoAgar  
both from batches in the United States and Australia. I have NEVER  
had a problem with PhytoAgar on root growth in root length assays up  
to a week. After that they are in the dish for too long and will  
suffer. One can supplement with sucrose in a standard quarter  
strength Hoaglands solution without problem. I agree you should not  
use MS medium or you will suffer from osmotic stress and perhaps  
other things that are out of balance for roots. The roots will grow  
without the sucrose but slower. It depends on your experiment, but  
those shaded cotyledons in a plastic petri dish can only do so much  
in the dark or dim light. I always grow them in the dark, as light  
inhibits root growth.
Grant R. Cramer
Professor
Department of Biochemistry and Molecular Biology, MS 200
University of Nevada, Reno
Reno, NV 89557
(775) 784-4204
cramer from unr.edu
http://www.ag.unr.edu/cramer/



On Feb 11, 2008, at 6:33 AM, Tobias Baskin wrote:

> Dear Tanya,
> 	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,
> 			Tobias
>
> At 3:10 PM -0600 2/9/08, Falbel, Tanya G. wrote:
>> Colleagues:
>>
>> 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.
>>
>> Thanks
>>
>> Tanya Falbel
>> Department of Biology
>> 105 Garfield Avenue
>> University of Wisconsin-Eau Claire
>> Eau Claire, WI 54702-4004,  USA
>>
>> Tel: 715-836-5087
>> Fax: 715-836-5089
>>
>>
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>
> -- 
>       _      ____          __   ____        /  \   /          /  
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