Chloroplast Division in the Gametophyte of the Fern Matteuccia Struthiopteris (l.) Todaro

The mechanism by which fully developed chloroplasts divide has been reported to consist of an initial constriction around the entire chloroplast, which is followed by a p inching into two daugh te r chloroplasts. Constr ict ion is accompanied by fusion of the inner and outer layers of the chloroplast membrane . Such a division has been documented by electron microscopy for the brown alga, Fucus (yon Wettstein, 1), and the red alga, Lomentaria (Bouck, 2). In Fucus the axis of division is usually parallel to the longitudinal axis of the chloroplast lamellae. Light microscopic observations of ma tu re chloroplasts dividing by constriction have been made in land plants ranging from bryophytes th rough the angiosperms (3, 4). Division of proplastids in higher plants (5) is similar to the condi t ion reported for algal chloroplasts, in tha t p inching also is accompanied by fusion of all the layers of the chloroplast membrane . A second method of mature chloroplast division is described in this paper. The ma tu re chloroplast is divided by the centr ipetal invaginat ion of the innerl imit ing membrane . This method of chloroplast division is here termed concentral ization. M A T E R I A L S A N D M E T H O D S