THE ULTRASTRUCTURE OF COTYLEDONARY TISSUE FROM GOSSYPIUM HIRSUTUM L. SEEDS

Abstract

Quiescent cottonseeds stored in a dry, anaerobic situation for over a year have been shown to contain cells whose contents are ultrastructurally similar to those of normal, fully hydrated plant cells. Plastids, mitochondria, and nuclei of the cells of cotyledon tissue in dry seeds possess normal-looking double membranes even under conditions of extreme desiccation. Previous reports have indicated on the basis of light microscopic work, that the cells of certain dry seeds do not possess nuclear membranes or mitochondria. The cells of the dry cottonseed do contain these structures, however. Dictyosomes have not been observed in the spongy parenchymal cells of the cotyledon tissue; it is suggested that they are concerned with translocation and/or utilization of material. The storage materials in the cells, protein and oil, are contained in vacuolar areas enclosed by a single membrane.Seeds offer a convenient base line in ontogenetic studies of the plant. Many ultrastructural studies have been directed to the terminal stages of seed development (7,8,12,17,27) or to the initial stages of seed germination (4,10,18,22,28), but relatively few studies have been conducted on the dry seed per se. Yet an understanding of the final changes on maturation and the first events of germination requires information on the mature, quiescent seed as a point of reference.Studies of biochemical changes in seeds which have initiated germination processes (1, 9, 31) show a dramatic rise in activity of many enzymes within a very short time. Wasserman (29), working with light microscopy, was unable to see mitochondria in cells of the dry seed. However, within 12 to 24 hours after the seeds had imbibed water, mitochondria in cells became visible, presumably arising de novo. Thus, it is obvious that changes occur quite rapidly in seeds after imbibition of water.Unfortunately, most electron microscope studies have been conducted on seeds which were allowed to imbibe water for various periods prior to fixation (16,18,25,28). Since rapid changes do occur in seeds upon imbibition of water, any technique involving imbibition of water, even for short periods, may not reflect their original condition. The paucity of studies on dry seeds is probably due to the extreme difficulty of working with them. This study, therefore, was undertaken to determine the structure of cells in dry, quiescent seeds fixed directly without prior hydration. MATERIALS AND METHODSA master sample of cottonseed (Gossypium hirsutum L., var. Acala 4-42-77, Glandless) harvested in Fall, 1962 was stored in a vacuum desiccator with a desiccant at 3°C and subsamples were removed as needed. Sections of tissue approximately 0.3 mm in diameter were cut carefully from the seed and fixed immediately in two different fixatives, osmium tetroxide and permanganate salts. OSMIUM :Since earlier work indicated that various solvents deranged the normal structure of the dry

Spherosome Membranes

“…Indeed, the membranes bounding spherosomes are not visible following permanganate fixation (24) and have confused a great many microscopists using other fixatives (9). Perhaps the appellation "interfacial structure" (14) might have been a more appropriate choice, since interfacial structures similar to these single-line membranes exist around certain fat droplets of artificially prepared emulsions.…”

Isolation and Characterization of Peanut Spherosomes

“…The affinity of spherosomes for lipophilic stains (6) and the relative abuindance of spherosomes in the storage tissuie of oil seeds (22) Electron Microscopy. Isolated spherosomes were embedded in an agar medium to facilitate manipulation through the fixation procedures.…”

An Electronmicroscopic Investigation of the Young Gametophyte of the FernBlechnum Spicant(L.) Roth.

“…(1963), Horncr S: Arnott (1965), Pcrncr (1965a and, Siniola (1969) and Yatsu (1965). Opik (1966), who studicd the finc structure of Pkaseoliis cotyledons during germination, found that thc storage cclls containcd, among other things, protein bodies, 2-22 ii in diamctcr and surrounded by a unit mcmbranc.…”