Partner Functions not appearing

Hi

When the PO is created manually, the Partner Function is being picked up from the Vendor Master. But when the PO is created for the same vendor with reference to the PR, the Partner Functions are not being populated in PO. The Vendor Master has Partner Functions defined and the Partner Schema is assigned to the concerned Puchasing Document type and Vendor Account Group. Any specific reason why the Partner Functions are not appearing in PO when created with ref. to PR?

Regards

Prashanth