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1.
ULF WIBERG 《Differentiation; research in biological diversity》1982,21(1-3):206-208
Anti H-Y antiserum, raised in highly inbred Lewis rats, was absorbed with gonadal cells from European eels of both sexes. It was found that rat anti H-Y antiserum cross-reacts with gonadal cells from the eel ovary but not with eel testicular cells. From these results it is suggested that in the European eel, the female is the heterogametic sex. 相似文献
2.
Abstract Net nitrate uptake rates were measured and the kinetics calculated in non-nodulated Pisum sativum L. cv. Marma and Lemna gibba L. adapted to constant relative rates of nitrate-N additions (RA), ranging from 0.03 to 0.27 d?1 for Pisum and from 0.05 to 0.40 d?1 for Lemna, Vmax of net nitrate uptake (measured in the range 10 to 100 mmol m?3 nitrate, i.e. ‘system I’) increased with RA in the growth limiting range but decreased when RA exceeded the relative growth rate (RGR), Km was not significantly related to changes in RA. On the basis of previous 13N-flux experiments, it is concluded that the differences in Vmax at growth limiting RA are attributable to differences in influx rates. Linear relationships between Vmax and tissue nitrogen concentrations were obtained in the growth limiting range for both species, and extrapolated intercepts relate well with the previously defined minimal nitrogen concentrations for plant growth (Oscarson, Ingemarsson & Larsson, 1989). Analysis of Vmax for net nitrate uptake on intact plant basis in relation to nitrogen demand during stable, nitrogen limited, growth shows an increased overcapacity at lower RA values in both species, which is largely explained by the increased relative root size at low RA. A balancing nitrate concentration, defined as the steady state concentration needed to sustain the relative rate of increase in plant nitrogen (RN), predicted by RA, was calculated for both species. In the growth limiting range, this value ranges from 3.5 mmol m?3 (RA 0.03 d?1) to 44 mmol m?3 (RA 0.21 d?1) for Pisum and from 0.2 mmol m?3 (RA 0.05 d?1) to 5.4 mmol m?3 (RA 0.03 d?1) for Lemna. It is suggested that this value can be used as a unifying measure of the affinity for nitrate, integrating the performance of the nitrate uptake system with nitrate flux and long term growth and demand for nitrogen. 相似文献
3.
ABSTRACT.
- 1 Larval performance of the leaf beetle Paropsis atomaria Oliver was determined for larvae raised on both new and mature leaves of Eucalyptus blakelyi Maiden. Larvae were transferred to mature leaves at different ages; control larvae stayed on new leaves through all instars.
- 2 Only larvae reared on new leaves through the third instar survived to pupate on mature leaves; developmental time was prolonged by 20% and pupal weight was reduced by 50% in these larvae compared with larvae reared entirely on new leaves. Almost all larvae died when transferred to mature leaves as first, second or third instars.
- 3 Low survival and slow development on mature leaves was mainly due to failure by larvae to feed. Larvae palpated leaves and could discriminate among leaf ages immediately, without biting into the leaf tissue.
- 4 New leaves had higher concentrations of oil and tannins than old leaves, while there were no significant differences in nitrogen concentrations in the two types of leaves. Mature leaves were more than 3 times tougher than new leaves, in terms of g mm?2 of penetrometer force.
- 5 In drought years E. blakelyi may not produce sufficient new leaves to supply specialist herbivores with their preferred food resource. We infer that drought years reduce P. atomaria larval performance significantly, and influence the population dynamics of the insect.
4.
Abstract.
- 1 Substantial intraspecific variation exists in Salix viminalis resistance to the gall midge Dasineura marginemtorquens. Earlier work has found this variation to have a large genetic component. Willow clones are stable in their resistances between midge generations and different nutrient levels in both field and laboratory culture.
- 2 This study reports the results of laboratory experiments on female oviposition choice and larval survival on potted plants from clones that are very different in resistance as determined in field studies.
- 3 In choice experiments using pairs of plants, the average female midge did not prefer susceptible willow clones over resistant ones for oviposition. In about one third of the replicates, midges actually laid more eggs on the resistant clone. Further work is necessary to examine the nature of variation among midges in discrimination of these plant types.
- 4 Resistance is manifested as great differences in larval survival. Six days after oviposition survival was 92% on susceptible plants but only 6% on resistant ones. Galls developed on all of the susceptible plants, while in 73% of the resistant plants galls were not even initiated.
- 5 The plant traits causing resistance are enigmatic. Larval behaviour suggests that resistant plants interfere with feeding behaviour. On resistant plants, most larvae wander for more than 24 h without initiating any galls before dying. On susceptible plants many first instar larvae begin feeding and initiate galls within this period.
5.
LARSSON MARIE; LARSSON CARL-MAGNUS; GUERRERO MIGUEL G. 《Journal of experimental botany》1985,36(9):1373-1386
Larsson, M., Larsson, C.-M. and Guerrero, M. G. 1985. Photosyntheticnitrogen metabolism in high and low CO2-adapted Scenedesmus.I. Inorganic carbon-dependent O2 evolution, nitrate utilizationand nitrogen recycling.J. exp Bot. 36: 13731386 Scenedesmus obtusiusculus Chod. was grown on an inorganic mediumflushed with either air or air supplemented with 3% CO2. Inair-grown cells, O2 evolution dependent on low, but not high,HCO3 concentrations was strongly inhibited by the carbonicanhydrase inhibitor acetazolamide. Cells grown with 3% CO2 exhibitedlow rates of O2 evolution at low external inorganic C; however,after 30 min in air O2 evolution rates at low inorganic C approachedthose of air-grown cells. These results are compatible withthe view that Scenedesmus develops a CO2 concentratingmechanism in air, with carbonic anhydrase as an importantconstituent When 3% CO2-grown cells were subjected to air-level of CO2,just a transient decline in NO3 utilization was observed,but in the presence of acetazolamide the rate of the processdecreased drastically in response to the decrease in the CO2level. In CO2-free air NO3 was taken up at high ratesbut in a deregulated manner, leading to release of NH4+. A portionof the NO3 taken up in the absence of CO2 was apparentlyassimilated Cellular nitrate reductase (NR) activity initially decreasedbut subsequently recovered after a transition from 3% CO2 toair. In the presence of acetazolamide, a persistent decreasein NR activity was observed. Cellular glutamine synthetase (GS)activity increased after transition from 3% CO2 to air, theactivity increase being unaffected by acetazolamide. NH4+ releaseto the medium in the presence of L-methionine-D, L-sulphoximine(MSO) transiently increased in 3% CO2-grown cells in responseto a transfer to air. MSO-induced NH4+ release was in fact higherin air-grown cells than in 3% CO2-grown cells. Glycollate wasinitially released after transition from 3% CO2 to air, butthere was no difference in glycollate release between MSO-treatedand untreated cells. In air-adapted Scenedesmus, N recyclingseems to be of minor importance in comparison to primary N assimilation Key words: CO2-fixation, N recycling, nitrate uptake, Scenedesmus 相似文献
6.
LARSSON CARL-MAGNUS; LARSSON MARIE; GUERRERO MIGUEL G. 《Journal of experimental botany》1985,36(9):1387-1395
Larsson, C.-M., Larsson, M. and Guerrero, M. G. 1985. Photosyntheticnitrogen metabolism in high and low CO2-adapted Scenedesmus.II. Effect of ammonium and methionine sulphoximine on nitrateutilization.J. exp. Bot. 36: 13871395 In 3% CO2-grown Scenedesmus obtusiusculus Chod. utilizing NO3J as the N source, NH4+ addition caused a prompt inhibitionof NO3 utilization. Nitrate reductase (NR) activity declinedrapidly in response to the presence of NO4+, but the cessationof NO3 utilization was too rapid to be accounted forby the loss in NR activity. The first site of NO4+ inhibitionin these cells seems to be the entrance of NO3 into thecells. Upon exhaustion of NO4+ from the medium, NO3 utilizationwas rapidly restored and NR activity increased. Air-grown cellswere much less sensitive to the effect of NO4+, more than 30min being required for added NO4+ to cause complete inhibitionof NO3 utilization. In these cells, NO3 uptakeand NR activity decreased in parallel in response to NO4+ addition.In 3% CO2-grown cells simultaneously subjected to NO4+ and air-levelof CO2, NO4+ initially inhibited NO3 utilization completely,but a slight recovery took place after approximately 20 min The glutamine synthetase (GS) inhibitor L-methionine D, L-sulphoximine(MSO) behaved as a potent inhibitor of NO3 uptake in3% CO2-grown cells, but had considerably less effect in air-growncells, although the time-course of the MSO-induced inhibitionof GS was the same in both cases Key words: Ammonium, nitrate utilization, Scenedesmus 相似文献
7.
Cosmine resorption structures on three osteolepid jaws and their biological significance 总被引:1,自引:0,他引:1
ULF J. BORGEN 《Lethaia: An International Journal of Palaeontology and Stratigraphy》1989,22(4):413-424
Cosmine resorption structures on three osteolepid jaws provide evidence for two different types of resorption process, one superficial and one initially internal. The superficial process starts in the pore canal openings. and the internal probably in the dentine pulp cavities or other cavities within the cosminc. Different stages of the superficial process that have previously not been recorded can he seen. Their positions show that superficial resorption may start in a few centers, from which it may spread in all directions but at different rates in different directions. There is no observable correspondence between the occurrence of resorption and the growth of the dermal bones along their sutures. Thus, the primary reason for resorption is not to allow marginal growth of the dermal bones. □ Cosmine resorption, osteolepids, Middle Devonian. 相似文献
8.
Mitochondrial DNA sequence diversity and the colonization of Scandinavia by house mice from East Holstein 总被引:3,自引:0,他引:3
9.
J. I. RONNY LARSSON 《The Journal of eukaryotic microbiology》1993,40(1):37-48
ABSTRACT. The microsporidium Chytridiopsis trichopterae n. sp., a parasite of the midgut epithelium of larvae of the caddis fly Polycentropus flavomaculatus found in southern Sweden, is described based on light microscopic and ultrastructural characteristics. All life cycle stages have isolated nuclei. Merogonial reproduction was not observed. the sporogony comprises two sequences: one with free spores in parasitophorous vacuoles, the other in spherical, 5.6-6.8 μm wide, sporophorous vesicles which lie in the cytoplasm. the free sporogony yields more than 20 spores per sporont. the vesicle-bound sporogony produces 8, 12 or 16 spores. the envelope of the sporophorous vesicle is about 82 nm thick and layered. the internal layer is the plasma membrane of the sporont; the surface layer is electron dense with regularly arranged translucent components. Both spore types are spherical. They have an ~ 35-nm thick spore wall, with a plasma membrane, an electron-lucent endospore, and an ~ 14-nm thick electron-dense exospore. the polar sac is cup-like and lacks a layered anchoring disc. the polar filament is arranged in two to three isofilar coils in the half of the spore opposite the nucleus. the coupling between the polar sac and the polar filament is characteristic. the surface of the polar filament is covered with regularly arranged membraneous chambers resembling a honeycomb. There is no polaroplast of traditional type. the cytoplasm lacks polyribosomes. the nucleus has a prominent, wide nucleolus. the two spore types have identical construction, but differ in dimensions and electron density. Free living spores are about 3.2 μm wide, the diameter of the polar filament proper is 102-187 nm, the chambers of the honeycomb are 70-85 nm high, and the polar sac is up to 425 nm wide. Living spores in the vesicle-bound sporogony are about 2.1 μm wide, the polar filament measures 69-102 nm, the chambers of the honeycomb are about 45 nm high, and these spores are more electron dense. Comparisons of cytology (especially the construction of the spore wall and the polar filament and associated structures) and life cycles reveal prominent differences among the Chytridiopsis-like microsporidia, and close relationships between the families Chytridiopsidae and Metchnikovellidae. 相似文献
10.
CURT BENGTSON BIRGITTA KLOCKARE STIG LARSSON CHRISTER SUNDQVIST 《Physiologia plantarum》1977,40(3):198-204
The influence of phytohormones on chlorophyll and carotenoid formation during the greening of irradiated dark grown wheat leaves (Triticum aestivum L. cv. Starke II Weibull) was studied. Leaves were floated on solutions of abscisic acid, gibberellic acid and kinetin for 24 h. The chlorophyll and carotenoid contents were determined during a subsequent period of 48 h of continuous irradiation. Leaves treated with abscisic acid showed a longer lag phase and a lower rate of accumulation of chlorophyll as compared to the control than did leaves treated with gibberellic acid and kinetin. The carotenoid content was low both in leaves treated with abscisic acid and in those treated with gibberellic acid. Treatment with abscisic acid lowered the protochlorophyllide regeneration after a saturating light flash while gibberellic acid as well as kinetin had no effect. The influence of ABA was partly dependent on an increase of the wounded part of the cut leaf segments. The accumulation of protochlorophyllide in leaves treated with δ-aminolevulinic acid was not affected by the different hormonal treatments. These results suggest that the main effect of abscisic acid is probably outside the chloroplast, i.e. on the formation or transport of δ-aminolevulinic acid. 相似文献