Minimum Water-to-Agar ratio?

[Ray]

I understand that agar powder will not dissolve in cold water, but that it has to be "activated" by heating. What is the minimum amount of water needed to activate 1 g of powder, and once activated and cooled, can additional liquid be combined with it? (I'm assuming the harder gel would have to be pureed...)

I have seen recommendations of 2.5-3.5 g/L. Would it be possible, let's say, to start with 5 g/L, and add more liquids after the fact?

 

[eteson]

I am not sure if I understand your question...

Three main factors should be considered.

1- Agar quality. Agar has not a chemical formulation... and you can find a wide range of qualities. For example Phytotech A111 can be used at 4 to 10 gr/l...
2- pH. Agar does not gel if the pH is too low.
3- Time of the exposition to Heat... Increasing times means lower strength on the agar.


In addition if you work at very low agar concentration you could have vitrification proplems... I usually work at 5 to 6 gr/l of A111 in Phrag flasks at pH of 5.2.

Hope it helps.

 

[Ray]

Thank you, Eliseo.

I have packets of food-grade agar. What I am trying to do is make a loose gel containing a substantial amount of KelpMax. I cannot mix the two and heat it to get gel formation, as that would destroy the hormones...

 

[eteson]

OK... you would need to make some tests... I would start at about 10gr /l of your agar but probably you are going to need more. You would also need to filter sterilize the kelp if it is for in vitro use.

 

[Ray]

Just an update -

For anyone interested in experimenting, I heard back from the manufacturer, and I was wrong. KelpMax can be autoclaved for a short period of time and not lose its rooting effectiveness - 120°C for 20 minutes was quoted - so it might be interesting to try it in replate flasks.

Storage at elevated temperature is a different thing...

 

[eteson]

Hi Ray, If the Kelp max is not too viscous, it could be filter-sterilized, because the autoclaving process always has a negative effect in hormones and vitamins.
To filter sterilize it you only need a sterile syringe and a disposable sterile filter (0.2 to 0.4 micrometers works fine).
Are you going to start making experiments?

 

[Trithor]

Food grade agar is not suitable as a medium gel for orchids as it contains too many impurities. There are a number of different classes and grades of tissue culture agars which have different gel strengths and purity. As has already been pointed out, the gel strength will be affected by temperature exposure and pH. If agar is dissolved and allowed to gel, you cannot add liquid to it afterwards and expect it to re-gel. It will take on the consistency of slime and will only reform a gel after reheating and allowing to re dissolve and then reset as the gel matrix is disrupted and does not reform without re dissolving. The gel strength will also not be anywhere near as strong and with some grades of agar will not re-gel at all the second time.
A replate medium using kelp as a nutrient source is an interesting idea (I suspect it has been tried already). I need to make up some replate medium in the next week or so, and am inclined to make a few using kelp to try alongside phytamax, orchidmax and a few others as a comparison.

 

[Ray]

KelpMax is about as viscous as water, but my goal in making up a relatively loose gel containing the KelpMax actually has nothing to do with seed culture, but is focused on a "cloning gel" request coming from growers of an entirely different type of "herbal" plant.

Trithor has given me some good guidelines, and I'll be using the food grade stuff just to experiment.

On another front - we were given a rather desiccated azalea. I presoaked some acrylate gel (Soil-Moist) in a KelpMax solution, then incorporated it in the soil when I planted it in our front flower bed, which is inside a cluster of Maples that suck the ground dry. The thing as responded beautifully, doing better than many of the others out there. At least until the maples infiltrate the area.


Ray Barkalow
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