Thanks for the many answers I got for the 2 questions I asked last week.
Here is a quick summary of what I have been told:
– Is tris a potential nitrogen source for Chlamy ?
As confirmed by everybody, Tris cannot be a MAJOR nitrogen source.
Some people (as I did too) use Tris in the media inducing gametogenesis. Now if we go into details and according to Olivier Vallon, photosynthetic mutants can grow (but very slowly) on a Tris media. Thus Tris can be metabolized and used as a carbon source (this however gives no evidence that Chlamy can use it as a nitrogen source). Well, here I am !!!
– Is there any non nitrogen pH buffer (except Phosphate) ? Here, I got also several answers. People are using HEPES (15 mM, pH 7.5), and also MOPES and PIPES as replacements/ supplements to Tris. Those 3 however contains nitrogen. It seems that growing Chlamy in liquid media under bubbling with 1% CO2 can maintain a steady state pH at values arround 6.8 – 7.0. So with this exception, no tracks of any nonnitrogen containing buffer other than phosphate.
Thanks again, Xav.