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51.
New information on Aegires ortizi Templado, Luque & Ortea,1987 is given, and two new species of the genus Aegires aredescribed, one from the Caribbean and one from the MediterraneanSea. A key to the North Atlantic species of Aegires is given. (Received 10 February 1989; accepted 11 July 1989) 相似文献
52.
Antigenic Makeup of Subcellular Fractions of Trypanosoma cruzi 总被引:1,自引:0,他引:1
ELSA LEONOR SEGURA ESTELA N. CURA IRENE PAULONE CESAR VASQUEZ JOSE A. CERISOLA 《The Journal of eukaryotic microbiology》1974,21(4):571-574
Trypanosoma cruzi epimastigotes from cultures were separated into nuclear, mitochondrial, lysosomal, microsomal, and cell-sap fractions. Enzymic and ultrastructutal controls served to determine the cleanness of separation. The bulk of the DNA was in the nuclear (78%) and mitochondrial (12%) fractions. RNA was found in microsomal (74%) and cell-sap (14%) fractions. Marker enzyme distribution (succinic dehydrogenase, acid phosphatase, and glucose-6-phosphatase) was compared with their distribution in mammalian tissues. Subcellular localization of antigens by Ouchterlony tests revealed 2 specific precipitin lines in cell sap and 1 in the microsomal fraction. These antigens may prove diagnostically and immunoprotectively valuable. 相似文献
53.
Red kidney bean (Phaseolus vulgaris L.) plants were grown in nutrient solution and in nutrient solution plus four bars of added NaCl. Chlorophyll and protein decay occurred much more rapidly in intact leaves from plants subjected to four bars of added NaCl in the growth medium than in intact leaves from plants without added NaCl. Ribonucleic acid (RNA) content in intact leaves of salt treated plants was higher than in intact leaves from plants grown in nutrient solution alone. However, the tendency for RNA content variation in leaves during the experimental period was the same for both control and salt treated plants. The results support the idea that salinity enhances senescence and suggests that hormone imbalance plays an important role in this process. 相似文献
54.
55.
Ultrastructural Changes in Cotyledons of Pineapple Guava (Myrtaceae) During Somatic Embryogenesis 总被引:3,自引:0,他引:3
Ultrastructural studies (SEM and TEM) were performed on cotyledonsof pineapple guava ( Feijoa sellowiana Berg, Myrtaceae) inducedto form embryos on medium containing 1.0 mg l-1(4.5µM2,4-D) and 0.3M sucrose. At the time of culture, the cells werefilled with protein and lipid bodies. Microbodies and poorlydifferentiated organelles could also be seen. In contrast togerminating cotyledons, where lipid and protein reserves werequickly metabolized, cells of the embryogenically induced cotyledonsshowed evidence of reserve consumption only after 5 d of culture.Subepidermal cells of the upper cotyledonary surface underwentseveral divisions giving rise to a meristematic layer of severalcells thickness from which somatic embryos developed. Embryoscould also be formed directly by successive divisions of epidermalcells. Cells involved in somatic embryo formation containeda large nucleus with a conspicuous nucleolus and dense cytoplasmwhere numerous ribosomes, mitochondria, plastids with starchand short profiles of rough endoplasmic reticulum were present.Plasmodesmata were present both in cell walls of the meristematiccells and in few celled embryos whereas in degenerating embryosor in more advanced stages of somatic embryo development noplasmodesmata could be found. Although oil bodies were not observedin the meristematic cells they were identified in very youngembryos, being the first reserve compounds to appear. Cellsnot involved in somatic embryo differentiation were characterizedby the presence of several microbodies containing a crystalloidinclusion and elongated mitochondria. Feijoa sellowiana ; pineapple guava; somatic embryogenesis; ultrastructural studies 相似文献
56.
N. PHILIP ASHMOLE PEDRO OROMÍ MYRTLE J. ASHMOLE JOSE L. MARTÍN 《Biological journal of the Linnean Society. Linnean Society of London》1992,46(1-2):207-234
Invertebrate communities in volcanic habitats of different ages on the islands of La Palma and El Hierro were studied using standardized trapping and searching techniques. A variety of graphical and numerical approaches were used to analyse relationships among the sites. Young, barren lava flows constitute aeolian ecosystems with a fauna of generalized detritivores and predators, especially collembolans, earwigs, thysamirans and crickets. Surface samples have many individuals and low diversity; those from caves have smaller numbers but similar taxonomic composition.
Vegetated surface habitats have richer communities, with diverse herbivores and predators but largely without the pioneer 'lavicolous' species. Caves with high humidity and stable temperature contain mainly specialized troglobitic species, but if there are both dry and humid sections lavicoles may also be present. Divergence into distinct epigean and hypogean communities results from both abiotic and biotic processes, including erosion and plant succession. While these occur mainly on the surface they also affect caves, increasing humidity and providing insulation from variations in external environmental conditions; the process is considered as a form of 'maturation' of the caves. Various models of succession are considered, which might help to account for the disappearance of lavicoles from mature epigean and hypogean communities. 相似文献
Vegetated surface habitats have richer communities, with diverse herbivores and predators but largely without the pioneer 'lavicolous' species. Caves with high humidity and stable temperature contain mainly specialized troglobitic species, but if there are both dry and humid sections lavicoles may also be present. Divergence into distinct epigean and hypogean communities results from both abiotic and biotic processes, including erosion and plant succession. While these occur mainly on the surface they also affect caves, increasing humidity and providing insulation from variations in external environmental conditions; the process is considered as a form of 'maturation' of the caves. Various models of succession are considered, which might help to account for the disappearance of lavicoles from mature epigean and hypogean communities. 相似文献
57.
ALBERTO BÚRQUEZ K. JOSE SARUKHÁAN ANA L. PEDROZA 《Botanical journal of the Linnean Society. Linnean Society of London》1987,94(4):407-419
A detailed account of the changes in visitor numbers and behaviour, inflorescence phenology, and breeding systems is presented. Inflorescences open early in the morning (05.00 hours). Stigmas remain receptive for 15 h, while anther dehiscence occurs 20 h after inflorescence opening. Maximum pollen viability occurs the next day at 05.00 hours. This combination of features largely precludes self-pollination. Controlled pollinations show that apomixis and auto-pollination are absent, and indicate strong incompatibility. In contrast, cross-pollinations do not differ in fruit set from open-pollinated controls. The fruit set in inflorescences exposed to pollinators for different periods after opening (and later stopping pollinator activity by fumigation), indicates that pollination occurs soon after inflorescence opening.
The visitors comprise a numerous and diverse fauna (15 families; 34 species). Features such as pollen loads, abundance, behaviour, and diet patterns, segregate them into: herbivores and predators (Aves, Orthoplera), pollen thieves (Apidae), and true pollinators (most Coleoptera and Diptera). The elevation in inflorescence temperature during opening, and 24 h later, is discussed in relation to cantharophily.
Astrocaryum mexicanum is an example of a highly diverse pollination system in which many animals can coexist. It represents an important resource during the dry season, and provides food and space for refuge and mating. The genetic consequences of having a host of pollinators with different dispersal capabilities are explored. 相似文献
The visitors comprise a numerous and diverse fauna (15 families; 34 species). Features such as pollen loads, abundance, behaviour, and diet patterns, segregate them into: herbivores and predators (Aves, Orthoplera), pollen thieves (Apidae), and true pollinators (most Coleoptera and Diptera). The elevation in inflorescence temperature during opening, and 24 h later, is discussed in relation to cantharophily.
Astrocaryum mexicanum is an example of a highly diverse pollination system in which many animals can coexist. It represents an important resource during the dry season, and provides food and space for refuge and mating. The genetic consequences of having a host of pollinators with different dispersal capabilities are explored. 相似文献
58.
BECANA MANUEL; APARICIO-TEJO PEDRO; PE?A JOSE; AGUIRREOLEA JONE; S?NCHEZ-D?AZ MANUEL 《Journal of experimental botany》1986,37(5):597-605
Nitrate and water stress were used to induce senescence in rootnodules of alfalfa (Medicago sativa L. cv. Aragon). Nodule senescencewas assessed by determinations of the nitrogenase (C2H2-reducing)activity, and the leghaemoglobin (LHb) and total soluble proteincontents of the nodules. Nodules responded similarly to and water stress in many respects, but there was a significant difference.All parameters of nodule activity, expressed on the basis ofnodule dry weight (DW), consistently decreased following treatmentwith or during drought; there was a significant interaction (synergism) between the inhibitory effects of and water stress on nitrogenase activity, but sucheffects were merely additive in the case of LHb content or LHb/solubleprotein ratio. However, caused the selective decay of LHb with respect to other nodular soluble proteins,whereas the decrease of LHb during water stress was due to ageneral inhibition of protein synthesis and to an increasedproteolytic activity in the nodule cytosol rather than to aspecific proteolysis of LHb. Key words: Leghaemoglobin, Medicago saliva, nitrogen fixation, root nodule senescence, water stress 相似文献
59.
60.
Recovery of Germination from Different Osmotic Conditions by Four Halophytes from Southeastern Spain 总被引:10,自引:0,他引:10
Seeds of four halophytes from southeastern Spain (the perennialsHalocnemum strobilaceum,Arthrocnemum macrostachyum and Sarcocorniafruticosa, and the annual Salicornia ramosissima) were exposedto iso-osmotic stress with NaCl, MgCl2, MgSO4and Na2SO4. Theosmotic potential that enforced dormancy in the majority ofseeds was determined. The percentage of ungerminated seeds thatrecovered when they were transferred to distilled water didnot differ significantly from the percentage germination ofseeds in distilled water controls, irrespective of the saltused to impose the stress. Therefore, the factor responsiblefor the dormancy of seeds seems to be the decrease in osmoticpotential. Such osmotic pretreatments promoted an increase inthe rate of recovery germination which, inArthrocnemum macrostachyumand Sarcocornia fruticosa, doubled their rates of germinationcompared to distilled water controls. The osmotic potentialsof the soils where the four species occur naturally were morenegative than those allowing seeds to germinate after osmoticstress. Copyright 2000 Annals of Botany Company Arthrocnemum macrostachyum, Halocnemum strobilaceum, halophytes, osmotic stimulation, recovery of seed germination, Salicornia ramosissima, Sarcocornia fruticosa. 相似文献