低浓度SO2长期暴露下菜豆的生长发育和气孔反应

本研究采用连续搅拌槽反应器系统(CSTR)对菜豆(Phaseolus vulgaris)进行低浓度SO_2长期暴露试验.结果表明,SO_2在植物可见伤害阈值以下抑制了莱豆生长,叶片气孔阻力随SO_2浓度的增加而增加.植物一旦脱离SO_2污染的环境,气孔就恢复到正常水平.切除子叶的菜豆生长明显受抑,但对SO_2敏感性和留子叶菜豆相同.     

Tectonic evolution of the Aravalli orogen (NW India): an inverted Proterozoic rift basin?

The Aravalli mountain range (AMR) in the northwestern part of the Indian Peninsula consists of two main Proterozoic metasedimentary and metaigneous sequences, the Aravalli and Delhi Supergroups, respectively, which rest over the Archaean gneissic basement. A synthesis and reinterpretation of the available geological, geochronological and geophysical data, including results of own field work and geophysical interpretations pertaining to the AMR, indicate its origin as an inverted basin: rifting into granitoid basement began ca. 2.5; Ga ago with Aravalli passive rifting (ca. 2.5–2.0 Ga) and Delhi active rifting (ca. 1.9–1.6 Ga). Associated mafic igneous rocks show both continental and oceanic tholeiitic geochemistry and are comparable with Phanerozoic, rift-related magmatic products. Available data showed no conclusive evidence for oceanic lithoshere and island-arc/active margin magmatic activity in the AMR. Subsequent inversion and orogeny (Delhi orogeny, ca. 1.5-1.4 Ga) lead to complex deformation and metamorphism. Only in the western and central zones has the basement been involved in this mid-Proterozoic (Delhi) deformation, whereas it is unaffected in the eastern part, except for local shear zones mainly along the basement/cover interface. The grade of metamorphism increases from the greenschist facies in the east to the amphibolite facies in the west with local HP assemblages. These latter are explained by rapid burial and exhumation of thin and cool continental lithosphere. Subsequently, during a final, mild phase of inversion, the Vindhyan basins consisting mainly of sandstones, limestones and shales, flanking the AMR formed which are comparable to foreland basins. The tectonic evolution of the AMR is therefore interpreted as an example of a major inverted continental rift and of a Proterozoic intra-continental orogen.     

Where Should Nature Reserves Be Located in South Africa? A Snake's Perspective

The present dispersion of nature reserves in South Africa is the historical result of a series of ad hoc decisions and may not be biologically optimal We have adopted a method to identify the optimal geography of nature reserves for the conservation of South Africa's snake fauna. The method of reserve selection operated on two tiers, and the spatial unit of analysis was a quarter-degree-square cell (∼625 km²). First, two scoring indices were used to rank cells with respect to species richness or to rarity. Second, two different iterative reserve-selection algorithms selected sets of cells (reserves), where each set represented all snake species at least once. Finally, the selected cells were examined for their present level of protection and their ranked scores. Depending on the algorithm chosen, only 23 or 29 cells were required to represent all species at least once; 72–78% of these cells already contained some level of protection; 59–70% of cells fell in areas of high species richness; and 72–91% of cells fell in areas with high rarity scores. Thus we conclude that most of the snake species in South Africa may be adequately protected with only modest acquisition of new reserves, and that the iterative algorithms appear to be efficient at siting cells in areas of high richness and rarity. We recommend that the reserve placement method outlined in this report be applied to as many other taxa as possible in the formulation of a national plan for an optimal reserve system for South Africa.     

Ecotypic differentiation of Laminaria longicruris in relation to seawater nitrate concentration

The ultraplankton (cell diameters >3 μm), which compromises about 70% of the biomass of phytoplankton in subtropical surface waters near Oahu, Hawaii, was isolated for growth rate studies. The specific growth rate (μ) was estimated from the rate of increase of the chlorophyll biomass during incubations in the absence of grazers. This growth rate of the ultraplankton ranged from 0.037 to 0.071 h^?1 (=1.3 to 2.5 doublings d^?1) during a period when P:B ratios of 5 to 14.5 μg C μg^?1 chl a h^?1 prevailed. The co-occurrence of atypically high P:B ratios and nonlimiting ambient nutrient concentrations suggests that the calculated values are higher than those characteristic of such subtropical ecosystems in general. Rates of ammonium uptake and photosynthesis by the >3 μm fraction were also compared to those of larger fractions. Organisms in the >3 μm fraction assimilated NH ₄ ⁺ at a rate which was about 75% greater than that of the 3 to 20 μm size fraction. Comparison of μ and P:B data collected over a 2 mo period (November–December, 1980) shows that the correlation between these two rate indices is nonlinear. The predominance of small-celled phytoplankton in oligotrophic waters is explained, in part, by its higher μ, its higher nutrient assimilation rates, and the absence of its loss through sedimentation.     

Patterns of the electric organ discharge during courtship and spawning in the mormyrid fish,Pollimyrus isidori

Summary Pollimyrus isidori's electric organ discharge (EOD) is of the pulse type. Patterns of EOD intervals were investigated prior to, during and following spawning behaviors as related with overt behaviors, and with the sound production by the nestbuilding male. Prior to the time of reproduction, isolated and socially interacting fish (n=15) showed characteristic discharge interval patterns for resting, swimming, probing, hovering and hiding activities. Males (n=8) and females (n=6) did not differ in their mean EOD repetition rates during resting (11.6±2.5 Hz), nor Short Bursts/min (less than 20 intervals of 8–13 ms). In interacting fish Long Bursts (greater than 20 intervals of 8–13 ms, lasting for more than 300 ms) were observed only during the attack and bite sequence. A pursuing fish displayed a rapid alternation of Long Bursts with Discharge Breaks (300–1000 ms silence) during the chase behavior. Avoidance behavior which followed from several attacks was correlated with a Medium Uniform Rate (8–12 Hz) normally lasting for 20 to 60 s, or a Discharge Arrest (silence greater than 1 s) in the submissive fish. The nocturnal courtship behavior began soon after dark (1900 h). Spawning typically started 2 to 5 h after dark, continuing for 2 to 6 h until about 0200 h. During courtship and spawning the female's brief visits (15–25 s) to the male's territory recurred every 30–60 s. At all other times the female was aggressively excluded from the nest region. Courtship and spawning behaviors are described along with the electrical displays identified from 19 spawnings in three fish pairs (from a total of 37 spawnings in 4 males and 4 females). Just prior to the onset of courtship behavior, with male territorial aggression beginning to decline, females switched from a Medium Sporadic Rate pattern (resting and hiding patterns; 13 Hz) to a Medium Uniform Rate pattern (6–8 Hz) while still in their hiding area. Females continued to display this uniform rate throughout the courship and spawning period, including the courtship and spawning bouts when Discharge Breaks or Arrests also occurred. This persistance distinguishes the courtship pattern from the similar avoidance pattern (see above). The male courtship and spawning EOD pattern was similar to the female's and unique for a territorial male. He switched from a High Sporadic Rate (swimming EOD pattern; about 18 Hz) to a regularized Medium Uniform Rate (about 9 to 11 Hz) only during courtship and spawning bouts, including 1–3 EOD Breaks during Vent-to-Vent coupling (average interval: 272±71 ms, n=37). No sooner had the female left the spawning site than he resumed displaying a High Sporadic Rate. This temporal correlation of reproductive behaviors with electrical displays suggests their instrumental role in mutual acceptance of mates. Males showed their sex-specific type of EOD phase-locking, the Preferred Latency Response, only during the first few hours of entry of a fish in their tank. Two females with EOD waveform features more typical of males also spawned repeatedly; waveform does not appear to be critical. Males stopped their nocturnal sound production for the later part of courtship and the whole spawning period. Except for infrequent attacks on the female between spawning bouts, the male did not resume singing until the end of spawning when all eggs were shed (around 0200 h); from this time on the male sang until dawn. The sequencing of the three acoustic elements (moans, grunts, growls) are described. A catalogue of discharge patterns correlated with overt behaviors (Tables 1, 2), and an integrated summary time table of P. isidori's complex reproductive behavior are presented.     

In situ measurement of the urea decomposition rate and its turnover rate in the Pacific Ocean

The in situ decomposition rate of urea was measured using ¹⁴C-labelled urea at 3 areas in the North Pacific Ocean: Sagami Bay on the southern coast of central Japan, the northwestern Pacific central waters and the subarctic Pacific waters. The mean values of the decomposition rates of urea in surface waters of these areas were 44.5, 1.51 and 1.32 mol urea m^-3 d^-1, respectively. These rates decreased with depth. High rates of urea carbon incorporation into particulate matter and the CO₂ liberation from urea carbon into seawater were obtained in light bottles in the euphotic zone, while low rates were found in dark bottles. The turnover rates of urea in the 3 areas were calculated respectively as 12, 113 and 110 d at the surface, and the values increased with depth.     

Combined effects of selenium/mercury and selenium/copper on the cell population of the alga Dunaliella minuta

The type of interaction of selenium and mercury, and selenium and copper on the cell growth of the planktonic alga Dunaliella minuta Lerche has been studied. The results for the various selenium/mercury and selenium/copper ratios showed that: (a) although mercury and selenium inhibited the growth of D. minuta when added to its cultures separately at levels greater than their respective threshold concentrations, they had antagonistic effects towards each other when added simulataneously at the beginning of growth; prior exposure of the culture to either metal for 2 d did not alter this antagonistic action; (b) similar antagonism was observed in combinations of selenium and copper for cultures with and without prior exposure to either metal. The reasons for the Se/Hg and Se/Cu antagonism are unknown; several hypotheses concerning possible detoxification mechanisms are proposed.     

Seasonal growth in Laminaria longicruris: Relations with dissolved inorganic nutrients and internal reserves of nitrogen

Observations have been made on seasonal fluctuations in dissolved inorganic nutrients, internal reserves of nitrogen and growth rates in Laminaria longicruris. The onset of winter growth in shallow-water stations (6 and 9 m) correlated well with improved dissolved nitrate conditions in the sea. During the winter, reserves of NO ₃ ^- were accumulated by the plants and reached maximum values of 150 moles per g fresh weight in March. This represents a concentration factor of approximately 28,000 over the ambient levels, or an internal nitrogen reserve of 2.1% of the dry weight of the tissue. Depletion of this nitrogen pool followed the disappearance of the external NO ₃ ^- with a lag period of up to 2 months. Rapid kelp growth was measured during this period. Reserves of organic nitrogen also reached maximum values in March and declined slowly throughout the summer into autumn. It is suggested that the combined inorganic and organic nitrogen reserves sustain the rapid growth rates into July and at reduced rate through the late summer. Fertilization of an experimental perimental kelp bed with NaNO₃ increased the internal plant reserves of NO ₃ ^- and produced a much improved summer growth rate. The enriched plants developed very small reserves of carbohydrate during the rapid summer growth phase.NRCC No. 15549.