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Change in the pH of stock solution - (Jul/23/2012 )

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fraffly on Wed Jul 25 10:19:05 2012 said:

This is just off the top of my head, I've never worked with seaweed cultures.
Seawater might contain some organic material that continues to degrade and change the pH, or the chemicals in the seawater might react with each other over time and alter compostition, maybe also under light (transparent bottles?).
Whats the plant regulator exactly ? Depending on the chemical make up it may form or catalyze reactions with other chemicals present ?
Other than that, what Crazy Xabi said are excellent points.

You could try a test series without plant regulator to see if it's the reason for the pH change. Or filter the seawater to get rid of some organic components.
Good luck !

I'm using IAA for the hormone and I've autoclave the seawater earlier. The bottles are kept in the lab, in room temperature, so I wonder do light really do affect the pH? Anyway thank you for your opinion my friend. This is helpful :)

-Ruth Grace-

mdfenko on Wed Jul 25 13:17:40 2012 said:

your problem is that the solutions are not buffered. co2 absorption will cause reduction of pH but if the solution warms up then co2 will desorb and you will experience an increase in pH.

you can add some buffer to the solutions to stabilize their pH.

Thank you for this opinion my friend. I'll have a try on this one. Just hope that the buffer doesn't affect the seaweed growth. Thank you again. :D

-Ruth Grace-

Ruth Grace on Wed Jul 25 08:32:10 2012 said:

Thank you for your opinion, pal. I did not autoclave the stock. Is it necessary to autoclave them?

Don't know if it is necessary, but some solutions can change the pH before and after autoclaving

One msds of IAA (link) states that is light sensitive.

You say you autoclave the seawater before adding the IAA, but the IAA... is it sterile? Some bugs may hide in the IAA flask :)

-El Crazy Xabi-

there are a number of relatively non-toxic buffers available for the pH range that you seem to require (~5.5): malate, benzoate, succinate, citrate, maleate...

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