I am looking for minimum tissue or water concentration of N and P to sustain growth for Lemna minuta and Landoltia punctata.

I did find minimum P in tissue for L. punctata: 6.3 mg P g-1 dry wt (Chaiprapat et al.2005)

and the minimum water P value for L. minuta growth: 0.00011 mM (Landolt).

However it is hard to compare these values and am therefore looking for any additional information.