I'll have to look for the paper, it might've even been posted on this board. I believe it was something like 36% avg.
*edit* perhaps I'm thinking of the fungi, there is one discussing adding these things to the substrate.
check out the paper "N,N-Dimethyltryptamine production in Phalaris Aquatica seedlings". it's in the 'more papers' thread. excellent paper, they discuss using tryptophan as a substrate. these divine plants express both tryptophan decarboxylase and tryptamine n-methyltransferase.
"Nothing is true, everything is permitted." ~ hassan i sabbah
"Experiments are the only means of attaining knowledge at our disposal. The rest is poetry, imagination." -Max Planck