Investments through participatory notes (P-notes) plunged to nearly nine-year low of Rs 1.06 lakh crore in the capital market at March-end amid stringent norms put in place by the regulator SEBI to check misuse of these instruments.P-notes are issued by registered foreign portfolio investors to overseas investors who wish to be part of Indian stock markets without registering themselves directly. They, however, need to go through a proper due diligence process.