Agar media - What am I doing wrong?
 

Hi Everyone

What am I doing wrong with my agar media? It contains charcoal, banana and coconut juice for sowing.

My problem is it is splitting I guess you would say. The charcoal is lumpy and sitts toward the bottom of the media when set. Shouldnt it be a evenly mixed? Will this matter much to the seed or with the nutrients be affected due to the stratification?

Why is it happening? Am I making the pressure cooker too hot or cooking it too long? I have tried a hot stove and at medium heat, for 15 mins to 25 mins. Still the same result. I dont have a guage on my pressure cooker.

I appreciate any advice.

Brett

Charcoal just doens't want to mix in. It often settles to the bottom. Banana can make things kind of lumpy if not homogenized.

How are you letting them cool? If you let them sit for a while to cool, try a more rapid cool down. Very slow cooling (letting them sit overnight in the sealed p-cooker) has been known to cause the agar to gel funny.

No gauge is OK for a p-cooker, as long as there is a weight that controls air release. If it does have a vent, you cant get any hotter than water's increased boiling temp at increased pressures (~230+). 15 psi for 15 minutes is fine.

When you stick it in the pressure cooker the medium will become partly liquid again and all the heavier components will tend to sink to the bottom. You just need to aggitate your prepared flasks while they cool in order to keep the ingredients evenly dispersed.

Thanks

The charcoal is dispersed, just not finely. I swirled the liquid agar while cooling, but some flasks look better than others. Will it make a lot of difference when sowing if it is a little stratified? Or will this really affect the germination?

With the banana, I put it through a very very fine sieve to make it like a very fine paste. So I think that just blended in along with the coconut juice. It is really just the charcoal I think that is the issue. The media has gelled ok too.

Brett

Hi again

I put the flasks in a pot of simmering water to melt the agar. I put them in the freezer to set it fast and swirled as it gelled. I got a good spread this time.

My only worry, is it ok to have some media - tiny bits - up the lowert walls of the flask. It is not up to the lid, but half way.

I tried to avoid this, but had to swirl it a good bit to make it mix. I think I will try another media brand next time. I wonder if it is just this brand.

Brett

I don't think this is really your problem Brett, but keep in mind that agar does not melt until the temperature reaches 100 degrees C (212f) and doesn't solidify until the temperature drops somewhere in the 40's degree C.