Correlated Light and Electron Microscope Studies on Brown Algae

Abstract

Summary The physodes or fucosan vesicles abundant in vegetative and reproductive cells of the brown seaweed Dictyota originate in the plastids. Precursor material expelled from the chloroplast matrix, may run together to produce the large physodes in the cell cytoplasm. Staining reactions indicate that the physodes are phenolic or tannin‐like in nature. They may be products of photosynthesis. Physodes in the apical region of thalli are exceedingly resistant and stable compared with those in older parts of thalli; the latter are lost during glutaraldehyde fixation.

Physodes and the Phenolic Compounds of Brown Algae. Composition and Significance of Physodes in vivo

“…While this idea was not widely accepted, Mangenot (1922) and Chadefaud (1927) attributed the metachromatic staining of physodes to their acidity. This conclusion was also reached by Kylin (1938), and was accepted by Evans and Holligan (1972b). Although Craigie and McLachlan (1964) reported the presence of carboxyl groups in vanillin-reactive exudates from Fucus vesiculosus examined by infrared spectrometiy, Ragan and Craigie (1975) found no carboxyl groups in purified vanillin-reactive compounds from F. vesiculosus.…”

“…A positive correlation between high metabolic activity and increased "fucosan" content has been noted by Crato (1893b), Richard (1929), Evans and Holligan (1972b), and others. Similarly, the younger, more actively growing parts of the thallus of Fucus vesiculosus are richer in "total phenols" than are other portions of the plant (Ragan, unpublished data).…”

“…Evans and Holligan (1972b) found no physodes in antheridia or in healthy unreleased eggs of D. dichotoma. Physodes disappear during zooidogenesis \r\Elachistafucicola andPylaiella littoralis (Loiseaux ' 1973).…”

“…The electron micrographs of Bisalputra (1966) faü to show a defmite physode membrane, and Bourne and Cole (1968) concluded on electron microscopic evidence that this point was "difficult to determine". Bisalputra et al (1971), Rawlence (1973), andPellegrini (1974) have reported a single membrane bounding the physode, while Evans and Holligan (1972b) suggested that the physode membrane was not the usual unit membrane. Much of this confusion arises from the uncertainty that individual osmiophilic bodies are physodes, and from the intense staining taken by many of these bodies.…”

“…183-189). Among the reagents tested were vanillin-hydrochloric acid, piperonal-sulfuric acid, and Feldmann and Guglielmi (1972) see text Oliveira and Bisalputra (1973) McCully (1968); Evans and Holligan (1972b); Feldmann and Guglielmi (1972) Bouck (1965); Chi (1971); Hori (1972) McCully (1966) McCully (l966)…”