CONDENSED TANNINS IN SAINFOIN .1. A HISTOLOGICAL AND CYTOLOGICAL SURVEY OF PLANT-TISSUES

Sainfoin (Onobrychis viciifolia Scop.) organs and tissues were surveye d for the presence of proanthocyanidins or condensed tannin (CT) in an attempt to learn more about CT formation. Three histological methods were used: a vanillin-HCI stain to localize areas of CT formation thro ugh a distinctive cherry-red coloration of CT-containing cells; osmium fixation to further localize CT formation in cellular organelles usin g light microscopy; and fine localization and examination using electr on microscopy. Cells containing CTs were found in relatively large num bers throughout the sainfoin plant in all organs except the roots. No CTs were found in the cotyledons or in some petals. Ultrastructural st udies revealed that CTs are restricted to the vacuoles and appear to a ccumulate on the inner periphery adjacent to the tonoplast or in the c entre of the organelle, possibly next to vacuolar invaginations.