Über den Aufbau pflanzlicher Zellwände

Ohne ZusammenfassungMit 12 Textabbildungen.     

Special secretory cells in the soybean seed coat

Summary The seed coat of soybean (Glycine max L. Merr.) is of physiological interest for synthesis and transport of amino acids and photosynthates during embryo development. A transmission and scanning electron microscopic study to elucidate the structure of the seed coat disclosed a specialized convex area (antipit) appressed to a concave pit in the center of the abaxial surface of the cotyledon. The antipit, which lies on the inner surface of the seed coat at a medial point in the anterior to posterior direction of the seed, contained specialized secretory cells bounded by loose multi-layered cell walls. These cells were rectangular in the developing seed, varied in length, and contributed directly to the convex morphology of the antipit seen on the ventral surface of the seed coat. At maturity these cells assumed the shape of a cone, extending from the aleurone layer in a perpendicular array. The aleurone and cone cells contained numerous Golgi apparatus, laminated rough endoplasmic reticulum, secretory vesicles, and amyloplasts. Secretory vesicles arose directly from tubules of fenestrated trans cisternae of the Golgi apparatus. Mitochondria were clustered with the amyloplasts; stacks of lamellar cisternae of rough endoplasmic reticulum were associated with the nucleus and Golgi apparatus. The cellular contents, the interconnections by plasmodesmata, and the close physical association with the cotyledon suggested that the aleurone and cone cells may be involved in symplastic transport of nutrients for use by the developing embryo.This paper is dedicated to the memory of my parents, Joseph and Theresa Yaklich, who by their example taught me the value of work and the enjoyment of simple things.     

ULTRASTRUCTURE OF THE SUBGLANDULAR CELLS FROM THE FOLIAR NECTARIES OF COTTON IN RELATION TO THE DISTRIBUTION OF PLASMODESMATA AND THE SYMPLASTIC TRANSPORT OF NECTAR

Foliar nectaries on the midveins of 7-cm leaves from cotton (Gossypium hirsutum L., cv. Stoneville 213) were examined by light and electron microscopy. The nectaries consist of external multicellular papillae and internal subglandular tissue that extends from the bases of the papillae to the vascular tissue of the midveins. The subglandular tissue is composed of small parenchyma cells; it does not contain sieve elements or xylem vessels. The parenchyma cells are rich in mitochondria, and their walls contain numerous pit fields having a high concentration of plasmodesmata. The absence of vascular tissue and the significance of the pit fields in the subglandular tissue are discussed in relation to symplastic transport of nectar secretions.     

An atypical crista resembling a "tight junction" in bean root mitochondria

The conformation and structure of an atypical crista found in a small percentage of the mitochondria in root tip cells of Phaseolus vulgaris L. have been studied electron microscopically in material fixed in glutaraldehyde followed by osmium tetroxide. In its transformation into an atypical crista, a normal crista elongates, broadens, and flattens, and the inner leaflets of its apposed unit membranes appear to fuse in a manner analogous to the formation of "tight junctions" between certain animal cells. The result is a large platelike, quintuple-layered structure, 240–260 A thick, whose long axis parallels that of the mitochondrion. The outer layers of the "plate," bordering on the mitochondrial matrix, are thickened and exhibit striking patterns in the micrographs. The structure of the plate is compared with that previously described for tight junctions between animal cells.     

Studies toward the comprehension of fungal-macroalgae interaction in cold marine regions from a biotechnological perspective

In marine ecosystems, macroalgae are the habitat for several microorganisms, fungi being among them. In the Antarctic benthic coastal ecosystem, macroalgae play a key role in organic matter cycling. In this study, 13 different macroalgae from Potter Cove and surrounding areas were sampled and 48 fungal isolates were obtained from six species, four Rhodophyta Ballia callitricha, Gigartina skottsbergii, Neuroglossum delesseriae and Palmaria decipiens, and two Phaeophyceae: Adenocystis utricularis and Ascoseira mirabilis. Fungal isolates mostly belonged to the Ascomycota phylum (Antarctomyces, Cadophora, Cladosporium, Penicillium, Phialocephala, and Pseudogymnoascus) and only one to the phylum Mucoromycota. Two of the isolates could not be identified to genus level, implying that Antarctica is a source of probable novel fungal taxa with enormous bioprospecting and biotechnological potential. 73% of the fungal isolates were moderate eurypsychrophilic (they grew at 5–25 °C), 12.5% were eurypsychrophilic and grew in the whole range, 12.5% of the isolates were narrow eurypsychrophilic (growth at 15–25 °C), and Mucoromycota AUe4 was classified as stenopsychrophilic as it grew at 5–15 °C. Organic extracts of seven macroalgae from which no fungal growth was obtained (three red algae Georgiella confluens, Gymnogongrus turquetii, Plocamium cartlagineum, and four brown algae Desmarestia anceps, D. Antarctica, Desmarestia menziesii, Himantothallus grandifolius) were tested against representative fungi of the genera isolated in this work. All extracts presented fungal inhibition, those from Plocamium cartilagineum and G. turquetii showed the best results, and for most of these macroalgae, this represents the first report of antifungal activity and constitute a promising source of compounds for future evaluation.     

Structure and development of P-protein in phloem parenchyma and companion cells of legumes.

Phloem parenchyma and companion cells from four species of legumes, Phaseolus vulgaris L., Melilotus alba Desr., Desmodium canadense, L. and Dolichos lablab L., were examined electron microscopically to estabish the presence, structure and development of P-protein. P-protein components consisting of granular, fibrillar, tubular or crystalline structures were found in parenchyma cells of all species and in companion cells of M. alba. The earliest stages of P-protein formation were closely associated with dictyosome cisternae, dictyosome vesicles and/or spiny vesicles. After their formation, the P-protein bodies were frequently transformed into one or more structurally different components. Although these components appeared to be develop-mentally related, their specific associations and transformations differed in each species examined.