Roots growth activator

[Intruder]

Dear all;
In orchids culture it is well know that phosphorus is a roots growth activator. For a given medium used in in-vitro culture, does also the increase in phosphorus level, have a positive effect on the roots growth , all other element concentrations remaining constant? I am interested to hear and share any comments on this subject.
Regards;
Claudy

[Ross]

As I understand it, B1 is a better stimulator. I use KLN which has 4.75%N + .011%P + .006%K but also has .025% Vitamin B1

[littlefrog]

I think the question is about plants in flask?

I'm sure there is research available on this, although I haven't read it. My guess is that phosphorous is not limiting in most standard media formulations.

Indeed, phosphorous is not limiting in most orchid fertilizer formulations, as demonstrated by many people, including some research here at Michigan State University by Dr. Biernbaum (I think that is how to spell his name). I think it depends a lot on the form in which phosphorous is available, I'm not really a fertilizer chemist so it gets hazy for me after that point.

[Intruder]

OK thank you for your answers. Indeed I read on the Net that a cymbidiums grower adds systematically 1ppm thiamin each time that he fertilizes his production.