Development of Observation Method for Isoflavones Secreted by Soybean Roots in Rhizobox Using Sheets with Immobilized Bovine Serum Albumin

A sensing method was developed to qualitatively evaluate the distribution of soybean isoflavones secreted by roots of soybeans transplanted into a simplified rhizobox by transferring them onto pieces of glass microfiber filter (sheets) with immobilized bovine serum albumin (BSA). To take advantage of fluorescence quenching by the interaction between BSA and soybean isoflavones, BSA was chemically bonded onto the sheets. The sheets with immobilized BSA were brought into contact with a nylon mesh (1 µm mesh aperture) of a simplified rhizobox, and secretions from soybean roots were transferred to the sheets. Fluorescence images before and after contact were captured with an electron-multiplying CCD camera to visualize and analyze fluorescence quenching. The results indicated that soybean isoflavone was spread within 2 to 3 mm from the roots.