[Electron dense substance of thylakoids in chloroplasts of tansy Tanacetum vulgare L].

An intrathylakoid electron opaque substance, further referred to as loculin, is found in 80-90 % of thylakoids of tansy leaf mesophyll chloroplasts at the stage of flower bud formation and flowering. Upon conventional isolation of chloroplasts in aqueous solution, and fixation in osmium solution alone, loculin is not retained in thylakoids. Preliminary fixation of leaves in glutaraldehyde makes it possible to isolate chloroplasts without injuring the envelope and stroma (glutar chloroplasts), and loculin is retained in thylakoids under these conditions. Upon prolonged incubation of glutar chloroplasts (for 24 h), loculin leaves thylakoids in the form of drops concentrating on the chloroplast envelope. Upon crossing the thylakoid membrane and chloroplast, loculin properties remain unchanged. It is assumed that loculin is an important metabolite necessary for active growth.