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21.
M. M. H. Kristensen J. I. Find F. Floto J. D. MØller J. V. NØrgaard P. Krogstrup 《Protoplasma》1994,182(1-2):65-70
Summary The development of somatic embryos in an embryogenic suspension culture ofPicea sitchensis was followed every day for two weeks after thawing from liquid nitrogen (LN2). Only a few cells, primarily located at the periphery of the embryonic region of the embryos, survived cryopreservation in LN2. Surviving cells were classified into two groups: embryogenic cells (EC) and non-embryogenic cells (NEC), based on their morphology and embryogenic competence. The dense cytoplasmic EC underwent organized growth and differentiation with first divisions occurring after 24 h, and embryo formation 6–8 days after thawing from LN2. No evidence of asymmetrical divisions or free-nuclear stages was found during somatic embryo formation. NEC had less dense cytoplasm with numerous small vacuoles. One to five days after thawing the NEC became progressively more vacuolated and elongated. Histological examination revealed no mitotic activity in NEC, and six days after thawing NECs were seen as single cells or unorganized cell aggregates. Two weeks after thawing the appearance of the cryopreserved cultures was comparable to that of the untreated cultures.Abbreviations EC
embryogenic cells
- ECC
embryogenic cell clusters
- FDA
fluorescein diacetate
- GMA
glycol methacrylate
- LN2
liquid nitrogen (–196°C)
- NEC
non-embryogenic cells 相似文献
22.
Kjetill Østgaard Mentz Indergaard Sidsel Markussen Svein H. Knutsen Arne Jensen 《Journal of applied phycology》1993,5(3):333-342
Anaerobic digestion of the brown algaLaminaria saccharina (L.) Lamour. harvested in spring and autumn was carried out at controlled laboratory conditions in stirred fermentor systems. Due to the normal seasonal variations, the autumn material had a much higher content of carbohydrates such as mannitol and laminaran. Both batch and semi-continuous feeding conditions were investigated for periods up to 800 h, with inoculum provided from previous kelp fermentations. In batch cultures, the methane yield from the autumn material was doubled compared to that of the spring material. Semi-continuous conditions gave more similar methane yields for both raw materials, 0.22 and 0.27 l CH4 per g VS for spring and autumn material, respectively. In all experiments, mannitol and laminaran were reduced to less than 5 of the initial values within 24–48 hours after inoculation, whereas 30 of the alginate content was detectable even after 30 days. Viscometry revealed that this material was severely depolymerized, and alginate lyase activity was found to develop rapidly in all cultures. Although mannitol and laminaran were fermented much faster than alginate, the total accumulated methane yields seemed to be determined by the total carbohydrate content of the raw material during extended semi-continuous feeding.(*author for correspondence) 相似文献
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24.
Ørjan Totland 《Oikos》2004,106(3):558-564
The preference for certain floral phenotypes by flower visiting animals may fuel the evolution of floral traits because variation in flower visitation rates may lead to fitness variation within a population. Here, I examine the importance of flower size for pollinator visitation rate, seed set, and seed mass in two alpine populations of the insect-pollinated herb Ranunculus acris L. during two seasons. There was no pollen limitation of seed set or mass. Pollinators discriminated strongly against flowers experimentally reduced in size. Despite this, there were no signs of any significant impact of flower size on female reproductive success. The results show that although pollinators discriminate strongly among floral phenotypes, this may not always result in female fitness differences within a population because seed set or mass is not limited by pollen availability alone. Probably abiotic environmental constraints prevent plants with high pollinator visitation from capitalizing on the high pollen deposition. 相似文献
25.
Symbiotic N2-fixation by the cover crop Pueraria phaseoloides as influenced by litter mineralization
The perennial legume Pueraria phaseoloides is widely used as a cover crop in rubber and oil palm plantations. However, very little knowledge exists on the effect of litter mineralization from P. phaseoloides on its symbiotic N2-fixation. The contribution from symbiotic N2-fixation (Ndfa) and litter N (Ndfl) to total plant N in P. phaseoloides was determined in a pot experiment using a 15N cross-labeling technique. For determination of N2-fixation the non-fixing plant Axonopus compressus was used as a reference. The experiment was carried out in a growth chamber during 9 weeks with a sandy soil and 4 rates of ground litter (C/N=16,2.8% N).
P. phaseoloides plants supplied with the highest amount of litter produced 26% more dry matter and fixed 23% more N than plants grown in soil with no litter application, but the percentage of Ndfa decreased slightly, but significantly, from 87 to 84%. The litter N uptake was directly proportional to the rate of application and constituted 10% of total plant N at the highest application rate. Additionally, a positive correlation was found between litter N uptake and the amount of fixed N2. The total recovery of litter N in plants averaged 26% at harvest (shoot + root) and was not affected by the quantity added. A parallel incubation experiment also showed that, as an average of all litter levels, 26% of the litter N was present in the inorganic N pool. The amounts of fertilizer and soil N taken up by plants decreased with litter application, probably due to microbial immobilization and denitrification. It is concluded that, within the litter levels studied, litter mineralization will result in a higher amount of N2-fixed by P. phaseoloides. 相似文献
26.
Christer Jansson Örjan Hansson Hans-Erik Åkerlund Lars-Erik Andreasson 《Biochemical and biophysical research communications》1984,124(1):269-276
EPR measurements on inside-out thylakoids revealed that salt-washing, known to inhibit oxygen evolution and release a 23 and a 16 kDa protein, induced a Signal IIf and decreased the EPR signal from state S2. Readdition of the released 23 kDa protein restored the oxygen evolution and decreased the Signal IIf, but did not relieve the decrease in the state S2 signal. It is suggested that salt-washing inhibits the electron transfer from the oxygen-evolving site to Z, the physiological donor to P680. In inhibited photosystem II units lacking Signal IIf, Z+ is rapidly reduced, possibly by a modified S-cycle unable to evolve oxygen. 相似文献
27.
Dr. T. S. Sætersdal R. Myklebust H. Engedal S. Ødegaarden 《Cell and tissue research》1978,186(1):13-24
Summary The substructure of the inner mitochondrial membranes has been studied by cryo-ultramicrotomy under conditions during which denaturation of proteins by treatment with chemical solutes has been totally avoided. In such preparations, the inner membrane has a substructure consisting of globular subunits. These subunits have an average diameter of ca. 20Å–ca. 62Å and are fairly regularly spaced. Intracristal space is absent in the unstained, freeze-dried preparations, whereas a space of ca 40Å is seen in preparations lightly treated by OsO4-vapour. It is concluded that the subunits of the inner mitochondrial membranes probably consist either of single protein molecules or of complexes of protein molecules.This work was supported by grants from The Norwegian Council on Cardiovascular Disease and from The Norwegian Research Council for Science and the Humanities 相似文献
28.
Niels Ørnbjerg Christensen Jesper Monrad Peter Nansen Flemming Frandsen 《Experimental parasitology》1980,49(1):116-121
Primary Schistosoma mansoni single-sex infections in mice, i.e., either male only or female only, did not stimulate any detectable level of heterologous resistance to challenge with Fasciola hepatica after 22 to 76 days, while statistically significant resistance to a challenge with F. hepatica was demonstrated in the presence of patent mixed-sex S. mansoni infections. Simultaneous infections with S. mansoni and F. hepatica induced a statistically significant reduction in the number of schisto-some worms established, i.e., the burden being reduced by 40.1 and 43.9%, respectively. There was no reduction of the F. hepatica worm burden. Similar features could be observed with a time interval of 48 hr between the S. mansoni infection and the F. hepatica challenge, i.e., the schistosome burden being reduced by 34.2 and 45.6%, respectively. Furthermore, simultaneous infections with S. mansoni and F. hepatica induced a statistically significant reduction of the egg production capacity per paired female schistosome worm as compared with that of the S. mansoni control group. Tissue egg counts of the various intestinal sections were reduced by 92.8–99.6%. 相似文献
29.
30.
Phosphoserine peptides, obtained by phosphorylation of synthetic precursors with cyclic AMP-dependent protein kinase, can be efficiently separated from the corresponding non-phosphorylated peptides and from each other by ion-pair high-performance liquid chromatography. All experiments were performed under isocratic conditions on a C18 column, using phosphate buffers with pH 3.2–4.5, n-hexane sulfonic acid as counter ion, and ethanol as organic modifier. 相似文献