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1.
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. 相似文献
2.
Low temperature field emission electron microscopy was used to determine the location of free water in soybean seeds. Frozen, hydrated soybean seeds were fractured, the water etched from the fractured surface, and then part of the etched surface was refractured. The resulting surface, which contained a freeze-fractured face as well as a freeze-etched face was coated with platinum and viewed on the cryostage of a low temperature field emission electron microscope. Two surfaces could be viewed simultaneously to determine the location of water in the seed tissue. Viewing the fractured surface gave an indication of the extent of hydration of the tissue. Viewing the etched surface detailed the macro- and microanatomy of the tissue. Viewing the intersection between the fractured and etched surfaces allowed observation of the environment of partially etched cells and organelles. The technique avoids artifacts associated with chemical fixation, dehydration, and critical-point drying, procedures that affect the water content of the seed. The technique does not affect the degree of hydration of the seed and can be used to localize water in the inter- and intracellular environment of the seed. This technique could find wide application in studies of water relationships of seeds during development, maturation, and imbibition. 相似文献
3.
The root-knot nematode Meloidogyne incognita was cultured monoxenically on excised tomato roots. Galls and egg masses were observed daily using a light microscope. Two phases were distinguished in the gelatinous matrix of the egg mass: a translucent, amorphous material on the surface of the egg mass and a denser, layered phase in which nematode eggs were deposited. Egg masses were also cryofixed, fractured, and observed as frozen, hydrated specimens on a cold stage in a scanning electron microscope (SEM). In the SEM, the layered phase appeared as a meshwork of fibrils that became more loosely associated as the gelatinous matrix aged: Small pearl-like bodies were observed along the fibers of gelatinous matrix. The egg shell surface and several stages of embryo development, including the one-cell stage, initial cleavages, blastula, gastrula, tadpole stage, elongation, and molt of the first-stage juvenile within the egg shell, were observed and photographed with this technique. The developmental events observed were consistent with those described in other nematode species with different techniques. 相似文献
4.
During the past 3 yr, nematologists in the United States have found specimens of Bursaphelenchus sp. in the wood of dead and dying pine trees. This nematode-host association resembles a similar interaction reported from Japan where pine trees are being killed by the pine wood nematode. This taxonomic research was conducted to determine if the Japanese pine wood nematode and similar populations in the United States are of the same species. Based upon typical morphological characters of original specimens of Bursaphelenchus xylophilus (Steiner and Buhrer 1934) Nickle 1970 that were rediscovered in the USDA Nematode Collection and genetic crosses among the Japanese and American nematode populations, it was concluded that they are all the same species, B. xylophilus. 相似文献
5.
This study examines the types of structural information that can be gained by utilizing the scanning electron microscope (SEM) and a cryofracture technique to examine the host-parasite interaction. Roots of tomato, Lycopersicon esculentum cv. Marglobe, were cultured aseptically and inoculated with the root-knot nematode, Meloidogyne incognita. Twenty-four hours to four weeks after inoculation, developing galls were removed from the cultures and processed for SEM observation. The cryofracture technique was used to reveal internal structural features within the developing galls. The results illustrate structural details concerning penetration of the roots, differentiation of syncytia, and development of the nematodes beginning with the second-stage larvae and ending with adult egg-laying females. 相似文献
6.
Ohne ZusammenfassungMit 12 Textabbildungen. 相似文献
7.
M.M. Martorell M. Lannert C.V. Matula M.L. Quartino L.I.C. de Figueroa WP Mac Cormack L.A.M. Ruberto 《Fungal biology》2021,125(3):218-230
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. 相似文献
8.
9.
An atypical crista resembling a "tight junction" in bean root mitochondria 总被引:3,自引:2,他引:1
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Eldon H. Newcomb Martin W. Steer Peter K. Hepler William P. Wergin 《The Journal of cell biology》1968,39(1):35-42
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. 相似文献
10.
Summary The morphology and fine structure of aleurone cells of soybean [Glycine max (L.) Merr.] seed coats were analyzed with transmission electron microscopy for the period of rapid seed fill up to physiological maturity. Thin sections and freeze-fracture replicas were prepared for each stage. The aleurone is a tissue lining the embryo sac and consists of a single layer of cells attached to the aerenchyma of the seed coat proper. During seed fill, aleurone cells contained numerous Golgi-derived vesicles in the basal region of the cytoplasm that were either free or attached to the plasma membrane along the lateral and basal regions of the cell wall. Correspondingly, the Golgi apparatus were well developed with individual dictyosomes having 5 to 8, highly fenestrated stacked cisternae. The degree of fenestration along the periphery of each cisterna increased from the cis to trans region. Rough endoplasmic reticulum (RER) was also abundant, often consisting of up to 30, stacked swollen cisternae which occupied large regions of cytoplasm. Plasmodesmata which connected adjacent aleurone cells was not observed along the dorsal walls of aleurone cells that faced aerenchyma. At physiological maturity, dictyosome cisternae were less fenestrated and had fewer associated secretory vesicles. Stacked lamellae of RER were absent, being replaced by short tubular cisternae and small vesicles. At physiological maturity, the aleurone cells had thick walls, and contained numerous lipid bodies in apposition to the plasma membrane. The cytoplasm appeared densely stained in thin-sections and contained protein bodies and amyloplasts with large starch grains. We conclude that during the period of rapid seed fill aleurone cells produce, package, transport and secrete vesicular contents toward the embryo, that is followed at physiological maturity by the storage of lipid, protein and starch in the same cells. The embryo is the most likely destination for secretory products during the period of rapid seed fill. The fate of the stored food reserves in aleurone cells at physiological maturity may be analogous to that of aleurone tissue of grasses, being utilized during imbibition for processes important to germination. 相似文献