Synthesis of a sesquiterpenoid phytoalexin rishitin in non-infected tissue from various parts of potato plants immediately after slicing

Rishitin synthesis was investigated in tissue by applying acetate-2-14C to tissue slices of various parts of potato cv. Rishiri and Yukijiro. Radioactivity of rishitin extracted from the tissue was ascertained by examining changes of radioactivities of bis (3, 5-dinitrobenzoate) of extracted rishitin on repeated recrystallization. The rishitin synthetic pathway showed significant operation in potato tuber disks within 30min after slicing, but little activity within 10min. With the slices of buds sprouted from tubers of cv. Rishiri and Yukijiro and those of seedlings of Rishiri, the synthetic pathway was shown to operate sufficiently within 10min after slicing. In the stem tissue 4cm from the top of the seedling, the synthetic pathway of rishitin was also found to operate within 10min after slicing, but synthetic activity was lower than in the bud tissue. These findings suggested that the rishitin synthetic pathway operates at the isotope level in an intact young potato tissue which is metabolically active, and is also induced rapidly in tuber tissue by wounding.