[PRECELLYS] Plant Sample: Phosphate and Sulfate assay

This  protocol  is  a  basic  and  can  be  used  for  different  purposes.  In our  lab  we  mostly  use  this  type  of  extraction  for  phosphate  and sulfate assay. Plants can take up only inorganic forms of phosphorus

– phosphates (P i ). P i  assay shows metabolically active phosphorus in a plant. Sulfur is available to plants primarily in the form of anionic sulfate  (SO 4   2− )  present  in  soil.  SO 4   2−   is  actively  transported  into roots  and  then  distributed,  mostly  unmetabolized,  throughout  the plant. SO 4   2−  assay reflects amount of sulfur taken up by plant.

The determination of P i  is based on the colorimetric method in which a  blue colour  is  formed  by  the  reaction  of  ortho-phosphate molybdate  ion  and  antimony  ion  followed  by  the  reduction  with ascorbic acid at an acidic  pH. The phosphomolybdenum complex is read at 620 nm. SO 4   2−  ion is  precipitated in a strongly acid medium with  barium  chloride.  The  resulting  turbidity  is  measured photometrically  at  420  nm.  In  both  assays  photometric  results  are compared with appropriate calibration standard solutions.