Fine structure of vegetative cells of Sphacelaria tribuloides Menegh. (Phaeophyceae, Sphacelariales) with special reference to some unusual proliferations of the plasmalemma

Abstract

Abstract The vegetative cells of Sphacelaria tribuloides possess an organization implying a strong photosynthetic activity. Regarding their detailed fine structure, they display most of the characteristic features of brown algal cells. In these are included: a continuity between the outer membrane of the nuclear envelope and the chloroplast endoplasmic reticulum (ER), an association of dictyosomes with either the outer nuclear membrane or ER membranes and the occurrence of plasmodesmata penetrating the cross walls. The microbodies of the vegetative cells of S. tribuloides resemble those of higher plant cells and constitute a distinct cytoplasmic entity. The plasmalemma generally displays irregularities but in definite regions it is considerably increased, forming a fretwork with a characteristic structure. Numerous finger-like plasmalemma ingrowths, projecting into the cytoplasm and partially surrounding well differentiated mitochondria, were observed in longitudinal and transverse sections. A transport r...