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951.
Responses of a C3 and a C4 perennial grass to elevated CO2 and temperature under different water regimes 总被引:1,自引:0,他引:1
H. W. HUNT †‡ E. T. ELLIOTT † J. K. DETLING †§ J. A. MORGAN ¶ D.-X. CHEN† 《Global Change Biology》1996,2(1):35-47
An experiment was carried out to determine the effects of elevated CO2, elevated temperatures, and altered water regimes in native shortgrass steppe. Intact soil cores dominated by Bouteloua gracilis, a C4 perennial grass, or Pascopyrum smithii, a C3 perennial grass, were placed in growth chambers with 350 or 700 μL L?1 atmospheric CO2, and under either normal or elevated temperatures. The normal regime mimicked field patterns of diurnal and seasonal temperatures, and the high-temperature regime was 4 °C warmer. Water was supplied at three different levels in a seasonal pattern similar to that observed in the field. Total biomass after two growing seasons was 19% greater under elevated CO2, with no significant difference between the C3 and C4 grass. The effect of elevated CO2 on biomass was greatest at the intermediate water level. The positive effect of elevated CO2 on shoot biomass was greater at normal temperatures in B. gracilis, and greater at elevated temperatures in P. smithii. Neither root-to-shoot ratio nor production of seed heads was affected by elevated CO2. Plant tissue N and soil inorganic N concentrations were lower under elevated Co2, but no more so in the C3 than the C4 plant. Elevated CO2 appeared to increase plant N limitation, but there was no strong evidence for an increase in N limitation or a decrease in the size of the CO2 effect from the first to the second growing season. Autumn samples of large roots plus crowns, the perennial organs, had 11% greater total N under elevated CO2, in spite of greater N limitation. 相似文献
952.
在体外观察了亚硒酸钠(Na_2SeO_3)作用于大鼠晶体上皮细胞(RLEcells)而引起其晶体蛋白基因转录的改变,对不同浓度的硒在体外对αA晶体蛋白基因转录的影响作了初步的研究。结果发现,随着亚硒酸钠浓度的升高,αA基因的转录下降;而当亚硒酸钠浓度升至5×10(-5)mo1/L时,αA基因的转录又呈反跳性回升。提示硒在致障过程中对晶体蛋白基因转录的影响作用不可忽视;同时αA晶体蛋白在晶体细胞内,至少应答于高浓度的硒,可能作为一种应激蛋白表达。 相似文献
953.
Mark V. Flinn Robert J. Quinlan Seamus A. Decker Mark T. Turner Barry G. England 《Human nature (Hawthorne, N.Y.)》1996,7(2):125-162
This study examines the family environments and hormone profiles of 316 individuals aged 2 months-58 years residing in a rural
village on the east coast of Dominica, a former British colony in the West Indies. Fieldwork was conducted over an eight-year
period (1988–1995). Research methods and techniques include radioimmunoassay of cortisol and testosterone from saliva samples
(N=22,340), residence histories, behavioral observations of family interactions, extensive ethnographic interview and participant
observation, psychological questionnaires, and medical examinations.
Analyses of data indicate complex, sex-specific effects of family environment on endocrine function. Male endocrine profiles
exhibit greater sensitivity to presence of father than do female endocrine profiles. Father-absent males tend to have (a) low cortisol levels during infancy, (b) high or abnormal cortisol profiles during childhood and adolescence, and (c) high cortisol and low testosterone levels during adulthood compared with those of males raised with a resident father. These
results indicate that early family environment has significant effects on endocrine response throughout male life histories.
Mark V. Flinn is an Associate Professor of Anthropology at the University of Missouri, Columbia. He studies family relationships,
endocrine stress response, and child health from a mix of evolutionary and developmental psychology perspectives.
Robert J. Quinlan is a graduate student in the Department of Anthropology at the University of Missouri, Columbia. His interests
include time allocation, family relationships, and medical anthropology. He is planning a long-term ethnographic study of
cross-cousin marriage among the E’nyepa of Venezuela.
Mark T. Turner is a graduate student in the Department of Anthropology at Northwestern University. He studies covariance of
mother and infant hormone and immune function in naturalistic settings using assays from saliva and breast milk samples and
ethnographic observations.
Seamus A. Decker is a graduate student in the Department of Anthropology at Emory University. He has studied social factors
associated with daily variations of salivary cortisol and testosterone levels among males in a Caribbean village. He is currently
investigating levels of stress in rural and urban populations in Botswana.
Barry G. England is an Associate Professor of Pathology and director of the ligand assay laboratories of the University of
Michigan Hospitals. His primary interests concern reproductive endocrinology. 相似文献
954.
Anderson Jan M. Dean Price G. Soon Chow Wah Hope Alex B. Badger Murray R. 《Photosynthesis research》1997,53(2-3):215-227
Tobacco transgenics with decreased amounts of the FeS apoprotein were generated using an antisense RNA construct targeted against the nuclear-encoded Rieske FeS protein of cytochrome bf complex [Price et al. (1995) Aust J Plant Physiol 22: 285–297]. FeS phenotypes ranging from intermediate to low were obtained which had 69% and 26% of the Rieske FeS protein of wild type. Similar reductions in the other subunits of cytochrome bf complex, cytochrome f, cytochrome b563and the 17 kDa subunit, were demonstrated in the thylakoids of intermediate and low FeS phenotypes. Confirmation that the levels of assembled cytochrome bf in leaves matched the levels of the FeS protein was demonstrated by laser flash-induced redox absorbance changes in leaves, with the extents of cytochrome f oxidation and cytochrome b563reduction being equivalent to the decreased amounts of the subunits in isolated thylakoids of the antisense plants. Despite greatly enhanced photochemical reduction of QAand the plastoquinone pool in the antisense plants, light acclimation of the FeS phenotypes to irradiance did not occur. Furthermore, the state 1–state 2 transitions were identical in wild type and antisense plants. Our results suggest that neither QAnor the plastoquinone pool acts alone in either the redox control of gene expression or the regulation of light energy distribution between the photosystems. We suggest rather that reduced plastoquinone acting at the inner Qpsite of cytochrome bf complex is involved in molecular redox signalling. 相似文献
955.
S. Egginton 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1997,167(2):129-134
The physiological responses to forced exercise were studied in yellowbelly and marbled rockcod (Notothenia coriiceps and N. rossii), and the haemoglobinless icefish (Chaenocephalus aceratus), from blood samples obtained via indwelling catheters. The maximal exertion tolerable by N. coriiceps was 3–5 min, although N. rossii was not fully exhausted by this effort, and it proved difficult to elicit sustained maximal activity in C. aceratus. Arterial O2 tension reflected the relative degree of exhaustion, showing a significant fall in the case of N. coriiceps, little change in N. rossii, and even a rise in C. aceratus as a result of hyperventilation. Such changes in the red-blooded species were not caused by altered O2 carrying capacity, as there was no change in haematocrit. In Notothenia spp. the decrease in arterial pH was better correlated with a rise in arterial CO2 tension than with blood lactate concentration, which is reflected in a modest net metabolic acid load. In contrast, the icefish
showed an attenuated hypercapnia and a more pronounced lactacidosis, but an insignificant net metabolic acid load. Disturbance
in ionoregulation following exercise was limited to an elevated [Cl−] in Notothenia, while circulating catecholamine levels remained unusually low in all specimens. The response to stress appears to reflect
lifestyle and/or endemic speciation, rather than specific adaptations to the stenothermal environment.
Accepted: 9 August 1996 相似文献
956.
E. Rhiel J. Marquardt M. Eppard E. Mrschel W. E. Krumbein 《Plant biology (Stuttgart, Germany)》1997,110(2):109-117
The main chlorophyll a/c light harvesting complex of the diatom Cyclotella cryptica was isolated by sucrose density gradient centrifugation. It consisted of two polypeptides of Mrs 18000 and 22000. Both polypeptides and fragments thereof, obtained by formic acid treatment, were blocked at their N-ter-mini. An antiserum raised against the two subunits selectively immunolabeled the thylakoid within the chloroplasts. The subunits were nuclear encoded and could be immunoprecipitated from poly (A)+ RNA as precursor proteins in the Mr range of 20000 to 24000. The existence of minor chlorophyll protein complexes and their possible function in light climate adaptation processes was investigated in cells adapted to low light and high light conditions. Low light grown cells contained more fucoxanthin and less β-carotene relative to chlorophyll a than high light adapted cells. The xanthophyll cycle pigments diatoxanthin and diadinoxanthin increased five-fold relative to chlorophyll a under high light conditions. Western-immunoblotting experiments with antisera raised against several chlorophyll a/b and chlorophyll a/c antenna complexes demonstrated that, beside the dominating chlorophyll a/c light harvesting complex, minor antenna complexes might exist, which, in part, seem to react to the light climate applied. 相似文献
957.
不同胁迫预处理提高水稻幼苗抗寒性期间膜保护系统的变化比较 总被引:39,自引:0,他引:39
通过比较盐、冷和热激三种不同胁迫预处理提高水稻(Oryza sativa L.)抗寒性过程中膜保护系统的变化,探讨植物交叉适应机理。结果表明,水稻幼苗经不同胁迫预处理均可提高幼苗的抗寒性。与未预处理苗相比,不同胁迫(冷、热、盐)预处理之间在处理后、低温伤害后及恢复2d后的3个不同时期膜酶促和非酶促保护系统及同工酶酶谱变化各有异同,既有部分共性,也有其独特性。 相似文献
958.
Everard J. Edwards David G. Benham† Louise A. Marland Alastair H. Fitter 《Global Change Biology》2004,10(2):209-227
Accurate knowledge of the response of root turnover to a changing climate is needed to predict growth and produce carbon cycle models. A soil warming system and shading were used to vary soil temperature and received radiation independently in a temperate grassland dominated by Holcus lanatus L. Minirhizotrons allowed root growth and turnover to be examined non‐destructively. In two short‐term (8 week) experiments, root responses to temperature were seasonally distinct. Root number increased when heating was applied during spring, but root death increased during autumnal heating. An experiment lasting 12 months demonstrated that any positive response to temperature was short‐lived and that over a full growing season, soil warming led to a reduction in root number and mass due to increased root death during autumn and winter. Root respiration was also insensitive to soil temperature over much of the year. In contrast, root growth was strongly affected by incident radiation. Root biomass, length, birth rate, number and turnover were all reduced by shading. Photosynthesis in H. lanatus exhibited some acclimation to shading, but assimilation rates at growth irradiance were still lower in shaded plants. The negative effects of shading and soil warming on roots were additive. Comparison of root data with environmental measurements demonstrated a number of positive relationships with photosynthetically active radiation, but not with soil temperature. This was true both across the entire data set and within a shade treatment. These results demonstrate that root growth is unlikely to be directly affected by increased soil temperatures as a result of global warming, at least in temperate areas, and that predictions of net primary productivity should not be based on a positive root growth response to temperature. 相似文献
959.
J. V. Arnekleiv H. A. Urke T. Kristensen J. H. Halleraker L. E. W. Flodmark 《Journal of fish biology》2004,64(2):541-552
Stress in wild brown trout Salmo trutta was assessed by sampling blood and measuring the concentrations of plasma cortisol and blood glucose in fish collected by electrofishing and immediately anaesthetized with metomidate. In the River Nidelva, Trondheim, Norway, the resting blood plasma cortisol concentration in the juvenile (0 + year) brown trout was 52 ± 44 nM (mean ± s .d .) in December and 2·3 nM (detection limit) in January. The corresponding blood glucose values were 1·8 ± 0·9 and 1·2 ± 0·2 mM, respectively. After electrofishing, handling and transport to the artificial stream, plasma cortisol and blood glucose levels increased significantly in both experiments. A maximum plasma cortisol level of 239 ± 120 and 71 ± 32 nM and a maximum blood glucose level of 3·9 ± 0·9 and 3·0 ± 0·9 mM were measured in the December and January stream channel experiments after transport, respectively. After introduction to the artificial stream, the blood plasma cortisol level returned to resting values within 24 h in the January stream channel experiment. The blood glucose levels remained at a higher level compared to the reference group throughout the December experiment, while it returned to resting values after 24 h in the January stream channel experiment. The major difference between the December and January experiments was the temperature within the artificial stream, 15–17° C in December and 7–9° C in January. This may have influenced the blood glucose levels. After dewatering of the artificial streambed there was a significant increase in plasma cortisol both in the December and January experiments, and after 24 h the plasma cortisol returned to the resting level in the January experiment. The blood glucose also increased during dewatering, although not significantly. 相似文献
960.