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61.
Shaking a leg and hot to trot: the effects of body size and temperature on running speed in ants 总被引:1,自引:0,他引:1
Abstract. 1. Data were compiled from the literature and our own studies on 24 ant species to characterise the effects of body size and temperature on forager running speed.
2. Running speed increases with temperature in a manner consistent with the effects of temperature on metabolic rate and the kinetic properties of muscles.
3. The exponent of the body mass-running speed allometry ranged from 0.14 to 0.34 with a central tendency of approximately 0.25. This body mass scaling is consistent with both the model of elastic similarity, and a model combining dynamic similarity with available metabolic power.
4. Even after controlling for body size or temperature, a substantial amount of inter-specific variation in running speed remains. Species with certain lifestyles [e.g. nomadic group predators, species which forage at extreme (>60 °C) temperatures] may have been selected for faster running speeds.
5. Although ants have a similar scaling exponent to mammals for the running speed allometry, they run slower than predicted compared with a hypothetical mammal of similar size. This may in part reflect physiological differences between invertebrates and vertebrates. 相似文献
2. Running speed increases with temperature in a manner consistent with the effects of temperature on metabolic rate and the kinetic properties of muscles.
3. The exponent of the body mass-running speed allometry ranged from 0.14 to 0.34 with a central tendency of approximately 0.25. This body mass scaling is consistent with both the model of elastic similarity, and a model combining dynamic similarity with available metabolic power.
4. Even after controlling for body size or temperature, a substantial amount of inter-specific variation in running speed remains. Species with certain lifestyles [e.g. nomadic group predators, species which forage at extreme (>60 °C) temperatures] may have been selected for faster running speeds.
5. Although ants have a similar scaling exponent to mammals for the running speed allometry, they run slower than predicted compared with a hypothetical mammal of similar size. This may in part reflect physiological differences between invertebrates and vertebrates. 相似文献
62.
LINGLI LIU JOHN S. KING FITZGERALD L. BOOKER† CHRISTIAN P. GIARDINA‡ H. LEE ALLEN SHUIJIN HU§ 《Global Change Biology》2009,15(2):441-453
Elevated CO2 has been shown to stimulate plant productivity and change litter chemistry. These changes in substrate availability may then alter soil microbial processes and possibly lead to feedback effects on N availability. However, the strength of this feedback, and even its direction, remains unknown. Further, uncertainty remains whether sustained increases in net primary productivity will lead to increased long‐term C storage in soil. To examine how changes in litter chemistry and productivity under elevated CO2 influence microbial activity and soil C formation, we conducted a 230‐day microcosm incubation with five levels of litter addition rate that represented 0, 0.5, 1.0, 1.4 and 1.8 × litterfall rates observed in the field for aspen stand growing under control treatments at the Aspen FACE experiment in Rhinelander, WI, USA. Litter and soil samples were collected from the corresponding field control and elevated CO2 treatment after trees were exposed to elevated CO2 (560 ppm) for 7 years. We found that small decreases in litter [N] under elevated CO2 had minor effects on microbial biomass carbon, microbial biomass nitrogen and dissolved inorganic nitrogen. Increasing litter addition rates resulted in linear increase in total C and new C (C from added litter) that accumulated in whole soil as well as in the high density soil fraction (HDF), despite higher cumulative C loss by respiration. Total N retained in whole soil and in HDF also increased with litter addition rate as did accumulation of new C per unit of accumulated N. Based on our microcosm comparisons and regression models, we expected that enhanced C inputs rather than changes in litter chemistry would be the dominant factor controlling soil C levels and turnover at the current level of litter production rate (230 g C m−2 yr−1 under ambient CO2). However, our analysis also suggests that the effects of changes in biochemistry caused by elevated CO2 could become significant at a higher level of litter production rate, with a trend of decreasing total C in HDF, new C in whole soil, as well as total N in whole soil and HDF. 相似文献
63.
ELLY P. H. BEST ALLEN M. TEETER KEVIN J. LANDWEHR WILLIAM F. JAMES SHYAM K. NAIR 《Freshwater Biology》2008,53(4):814-826
1. Restoration of shallow turbid lakes to promote growth of submersed aquatic vegetation (SAV) requires knowledge of the environmental factors affecting SAV growth and persistence, and a means to predict the success of SAV reestablishment under different management scenarios to improve these environmental conditions. We used a dynamic ecological modelling approach relating SAV responses to changes in physical and chemical conditions, with information on water level, flow and transparency being provided by hydrodynamic and sediment transport models. 2. The potential persistence of Vallisneria americana was similar under simulated environmental conditions in 1946 and in 1954, as was the potential persistence of Potamogeton pectinatus, indicating that the disappearance of V. americana from Peoria Lake (U.S.A.) previously attributed to an extended spring flood in 1954, may have been related to the combined effects of changes in water level, flow and water transparency as well as possibly other factors. 3. Recent environmental conditions (for 2000) proved not to be conducive for the colonization and persistence potential of V. americana, but would allow colonization by P. pectinatus. The construction of a hypothetical levee along the eastern descending line of the navigation channel in Upper Peoria Lake, which was expected to reduce fetch‐ and navigation‐related turbidity, did not improve the situation for V. americana and overall deteriorated the situation for P. pectinatus. Thus, such a hydraulic alteration, generally considered as beneficial for SAV restoration, may not always be successful. 4. The results of the simulations indicated that the environmental conditions for potential persistence in Peoria Lake were generally less favourable for V. americana than for P. pectinatus. Measures suggested to restore SAV communities in such a lake should aim at reducing concentrations of total suspended solids at the point of inflow by a factor of three to four and limiting fetch‐ and navigation‐related resuspension. 相似文献
64.
The effect of micronutrient supply on the growth and seed production of guayule (Parthenium argentatum Gray) was investigated. A deficiency of boron, but no other trace element, significantly reduced the growth, seed production and the percentage of seeds that germinated. The optimum concentration of B for seed production was between 20 and 100 μM. Results indicate that guayule may benefit from B fertilisation. 相似文献
65.
Ricinus communis L. var. Gibsonii was grown in Long Ashton nutrientmedium with either 12mol m3 NO3 or 8.0 mol m3NH+4 as N source. Two plants from each N treatment were harvestedtwice a week and analysed for C, N, P, S, NO3, SO24ClK+Na+, Ca2+ Mg2+ and ash alkalinity. Statistical analysis of thedata showed that the effect of age and N source was differentfor the chemical variables analysed. Thus [Na+] was unaffectedby age or N source, and for both N sources [Mg2+] started atthe same level and decreased at the same rate as the plantsmatured. With NH+4 as N source, [SO24] was higher thanwith NO3, but did not alter with age. The concentrations,in mmol g1 dry wt, of C, organic N, K+ and Ca2+ weredifferent for the two N sources, but the levels of these variablesaltered with age in the same way for both N sources; i.e. therewas no age x N interaction. In the case of P, NO3, Cl and COO, however,age-related variations were different for the two N sources.It is concluded, inter alia, that [Na+] is determined by external[Na+] alone, and that K+, Ca2+ and Cl are the inorganicions actively involved in charge balance during ion uptake bythe roots. Key words: Ontogeny, Chemical composition, Plant nutrition 相似文献
66.
CAMPBELL WILLIAM J.; ALLEN L. H. JR; BOWES GEORGE 《Journal of experimental botany》1990,41(4):427-433
Photosynthetic rates of outdoor-grown soybean (Glycine max L.Merr. cv. Bragg) canopies increased with increasing CO2 concentrationduring growth, before and after canopy closure (complete lightinterception), when measured over a wide range of solar irradiancevalues. Total canopy leaf area was greater as the CO2 concentrationduring growth was increased from 160 to 990 mm3 dm3.Photosynthetic rates of canopies grown at 330 and 660 mm3 CO2dm3 were similar when measured at the same CO2 concentrationsand high irradiance. There was no difference in ribulose bisphosphatecarboxylase/oxygenase (rubisco) activity or ribulose 1,5-bisphosphate(RuBP) concentration between plants grown at the two CO2 concentrations.However, photosynthetic rates averaged 87% greater for the canopiesgrown and measured at 660 mm3 CO2 dm3. A 10°C differencein air temperature during growth resulted in only a 4°Cleaf temperature difference, which was insufficient to changethe photosynthetic rate or rubisco activity in canopies grownand measured at either 330 or 660 mm3 CO2 dm3. RuBP concentrationsdecreased as air temperature during growth was increased atboth CO2 concentrations. These data indicate that the increasedphotosynthetic rates of soybean canopies at elevated CO2 aredue to several factors, including: more rapid development ofthe leaf area index; a reduction in substrate CO2 limitation;and no downward acclimation in photosynthetic capacity, as occurin some other species. Key words: CO2 concentration, soybean, canopy photosynthesis 相似文献
67.
68.
Right-side-out plasma membrane vesicles were isolated from wheat roots using an aqueous polymer two-phase system. The purity and orientation of the vesicles were confirmed by marker enzyme analysis. Membrane potential (Ψ)-dependent 22Na+ influx and sodium/proton (Na+/ H+) antiport-mediated efflux across the plasma membrane were studied using these vesicles. Membrane potentials were imposed on the vesicles using either K+ gradients in the presence of valinomycin or H+ gradients. The ΔΨ was quantified by the uptake of the lipophilic cation tetraphenylphosphonium. Uptake of Na+ into the vesicles was stimulated by a negative ΔΨ and had a Km for extrav-esicular Na+ of 34.8 ± 5.9 mol m3. The ΔΨ-dependent uptake of Na+ was similar in vesicles from roots of hexaploid (cv. Troy) and tetraploid (cv. Langdon) wheat differing in a K+/Na+ discrimination trait, and was also unaffected by growth in 50 mol m?3 NaCl. Inhibition of ΔΨ-dependent Na+ uptake by Ca2+ was greater in the hexaploid than in the tetraploid. Sodium/proton antiport was measured as Na+-dependent, amiloride-inhibited pH gradient formation in the vesicles. Acidification of the vesicle interior was measured by the uptake of 14C-methylamine. The Na+/H+ antiport had a Km, for intravesicular Na+ of between 13 and 19 mol m?3. In the hexaploid, Na+/H+ antiport activity was greater when roots were grown in the presence of 50 mol m?3NaCl, and was also greater than the activity in salt-grown tetraploid wheat roots. Antiport activity was not increased in a Langdon 4D chromosome substitution line which carries a trait for K+/Na+ discrimination. It is concluded that neither of the transport processes measured is responsible for the Na+/K+ discrimination trait located on the 4D chromosome of wheat. 相似文献
69.
Previous studies indicated that pituitary hormone induced oocyte maturation in preovulatory amphibian ovarian follicles is mediated by somatic elements of the follicle. In this study procedures were developed for isolating and culturing follicle cells and their ability to produce meiosis inducing substance (MIS) was assessed. Defolliculated oocytes surrounded by a single layer of follicle cells but not denuded oocytes matured in response to frog pituitary hormone (FPH) stimulation. Cultured follicle cells secreted MIS following stimulation with FPH. The amount of MIS activity produced was related to the number of follicle cells cultured and the dose of FPH utilized. Radioimmunoassay (RIA) analysis of medium from follicle cell cultures demonstrated that FPH stimulated steroid (progesterone) secretion from these cells. Addition of cAMP to follicle cell cultures enhanced FPH stimulated steroid production. The results indicate that follicle cells retain FPH responsiveness when uncoupled from the immature oocyte and exhibit both MIS and steroid secretory functions. 相似文献
70.