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71.
植物对重金属锌耐性机理的研究进展 总被引:3,自引:1,他引:3
Zn是植物必需的营养元素,同时也是一种常见的有毒重金属元素.由于长期的环境选择和适应进化,植物相应对Zn~(2+)产生了耐性,可减轻或避免Zn~(2+)的毒害.植物对锌耐性机制有:菌根和细胞膜对Zn~(2+)吸收的阻止和控制,其中控制Zn~(2+)的细胞膜跨膜转运器主要有(ZIP)类、阳离子扩散促进器(CDF)类和B-type ATPase (HMA)类;金属硫蛋白(MTs)、植物螯合素(PCs)和有机酸等Zn~(2+)螯合物质的体内螯合解毒;体内区室化分隔以及通过抗氧化系统和渗透调节物质的代谢调节等.本文从生理和分子水平上综述了植物对Zn~(2+)耐性机理的研究进展,并在此基础上提出目前存在的问题和今后研究的重点领域,为该领域的相关研究提供资料和借鉴. 相似文献
72.
D. A. PELTZER R. B. ALLEN G. M. LOVETT D. WHITEHEAD D. A. WARDLE 《Global Change Biology》2010,16(2):732-746
There has been a rapidly developing literature on the effects of some of the major drivers of global change on carbon (C) sequestration, particularly carbon dioxide (CO2) enrichment, land use change, nitrogen (N) deposition and climate change. However, remarkably little attention has been given to one major global change driver, namely biological invasions. This is despite growing evidence that invasive species can dramatically alter a range of aboveground and belowground ecosystem processes, including those that affect C sequestration. In this review, we assess the evidence for the impacts of biological invaders on forest C stocks and C sequestration by biological invaders. We first present case studies that highlight a range of invader impacts on C sequestration in forest ecosystems, and draw on examples that involve invasive primary producers, decomposers, herbivores, plant pathogens, mutualists and predators. We then develop a conceptual framework for assessing the effects of invasive species on C sequestration impacts more generally, by identifying the features of biological invaders and invaded ecosystems that are thought to most strongly regulate C in forests. Finally we assess the implications of managing invasive species on C sequestration. An important principle that emerges from this review is that the direct effects of invaders on forest C are often smaller and shorter‐term than their indirect effects caused by altered nutrient availability, primary productivity or species composition, all of which regulate long‐term C pools and fluxes. This review provides a conceptual basis for improving our general understanding of biological invaders on ecosystem C, but also points to a paucity of primary data that are needed to determine the quantitative effects of invaders on ecosystem processes that drive C sequestration. 相似文献
73.
ANDERS MALMER DANIEL MURDIYARSO L. A. BRUIJNZEEL ULRIK ILSTEDT 《Global Change Biology》2010,16(2):599-604
Tree planting in the tropics is conducted for a number of reasons including carbon sequestration, but often competes with increasingly scarce water resources. The basics of forest and water relations are frequently said to be well understood but there is a pressing need to better understand and predict the hydrological effects of land‐use and climate change in the complex and dynamic landscapes of the tropics. This will remain elusive without the empirical data required to feed hydrological process models. It is argued that the current state of knowledge is confused by too broad a use of the terms ‘forest’ and ‘(af)forestation’, as well as by a bias towards using data generated mostly outside the tropics and for nondegraded soil conditions. Definitions of forest, afforestation and reforestation as used in the climate change community and their application by land and water managers need to be reconciled. 相似文献
74.
Chelation by histidine inhibits the vacuolar sequestration of nickel in roots of the hyperaccumulator Thlaspi caerulescens 总被引:2,自引:0,他引:2
75.
Taro Masuda Fumiyuki Goto Bunzo Mikami 《Biochemical and biophysical research communications》2010,400(1):94-99
Ferritins are ubiquitous iron storage proteins. Recently, we identified a novel metal-binding site, transit site, in the crystal structure of phytoferritin. To elucidate the function of the transit site in ferritin from other species, we prepared transit-site-deficient mutants of human H ferritin, E140A and E140Q, and their iron oxidation kinetics was analyzed. The initial velocities of iron oxidization were reduced in the variants, especially in E140Q. The crystal structure of E140Q showed that the side chain of the mutated Gln140 was fixed by a hydrogen bond, whereas that of native Glu140 was flexible. These results suggest that the conserved transit site also has a function to assist with the metal ion sequestration to the ferroxidase site in ferritins from vertebrates. 相似文献
76.
MARCELO VALADARES GALDOS CARLOS CLEMENTE CERRI RATTAN LAL† MARTIAL BERNOUX‡ BRIGITTE FEIGL CARLOS EDUARDO P. CERRI§ 《Global Change Biology Bioenergy》2010,2(1):37-44
Biofuels are both a promising solution to global warming mitigation and a potential contributor to the problem. Several life cycle assessments of bioethanol have been conducted to address these questions. We performed a synthesis of the available data on Brazilian ethanol production focusing on greenhouse gas (GHG) emissions and carbon (C) sinks in the agricultural and industrial phases. Emissions of carbon dioxide (CO2) from fossil fuels, methane (CH4) and nitrous oxide (N2O) from sources commonly included in C footprints, such as fossil fuel usage, biomass burning, nitrogen fertilizer application, liming and litter decomposition were accounted for. In addition, black carbon (BC) emissions from burning biomass and soil C sequestration were included in the balance. Most of the annual emissions per hectare are in the agricultural phase, both in the burned system (2209 out of a total of 2398 kg Ceq), and in the unburned system (559 out of 748 kg Ceq). Although nitrogen fertilizer emissions are large, 111 kg Ceq ha?1 yr?1, the largest single source of emissions is biomass burning in the manual harvest system, with a large amount of both GHG (196 kg Ceq ha?1 yr?1). and BC (1536 kg Ceq ha?1 yr?1). Besides avoiding emissions from biomass burning, harvesting sugarcane mechanically without burning tends to increase soil C stocks, providing a C sink of 1500 kg C ha?1 yr?1 in the 30 cm layer. The data show a C output: input ratio of 1.4 for ethanol produced under the conventionally burned and manual harvest compared with 6.5 for the mechanized harvest without burning, signifying the importance of conservation agricultural systems in bioethanol feedstock production. 相似文献
77.
Angiogenesis, i.e., new blood vessel formation, is required in normal and pathological states. A dysfunction in the microvascular
endothelium occurs in diabetes, leading to decreased blood flow and limb amputation. In cancer, angiogenesis is increased
to allow for growth, invasion, and metastasis of tumor cells. Better understanding of the molecular events that cause or are
associated with either of these diseases is needed to develop therapies. The tumor and angiogenic cells micro-environment
is acidic and not permissive for growth. We have shown that to survive this environment, highly metastatic and angiogenic
cells employ vacuolar H+-ATPase at their plasma membranes (pmV-ATPases) to maintain an alkaline pHcyt. However, in lowly metastatic and in microvascular endothelial cells from diabetic model, the density of pmV-ATPase and the
cell invasiveness are decreased. Therefore, the overexpression of the pmV-ATPase is important for cell invasion, and essential
for tumor progression, angiogenesis and metastasis. Both, cancer and diabetes are heterogenous diseases that involve many
different proteins and signaling pathways. Changes in pHcyt have been associated with the regulation of a myriad of proteins, signaling molecules and pathways affecting many if not
all cellular functions. Since changes in pHcyt are pleiotropic, we hypothesize that alteration in a single protein, pmV-ATPase, that can regulate pHcyt may explain the dysfunction of many proteins and cellular pathways in diabetes and cancer. Our long term goal is to determine
the molecular mechanisms by which pmV-ATPase expression regulates tumor angiogenesis and metastasis. Such knowledge would
be useful to identify targets for cancer therapy. 相似文献
78.
Daniel Obrist 《Biogeochemistry》2007,85(2):119-123
Plants accumulate significant amounts of atmospheric mercury (Hg) in aboveground biomass, likely sequestering over 1,000 Mg
of atmospheric Hg every year. This large mercury uptake could be strong enough to affect tropospheric Hg levels and might
be partially responsible for seasonal variations in atmospheric Hg observed at Mace Head, Ireland. The fluctuations of Hg
concentrations coincide temporally with the annual oscillation of carbon dioxide (CO2) in the Northern Hemisphere, which is a result of seasonal growth of vegetation. Therefore, declining Hg concentrations in
spring and summer may be attributed in part to plant uptake of atmospheric Hg. Further, the increase of Hg concentrations
during non-active vegetation periods might partially be due to plant-derived Hg emitting back to the atmosphere during carbon
mineralization. The implications of these propositions are that past and future changes in biomass productivity and organic
carbon pools may have had—and may continue to have—significant effects on atmospheric Hg levels. Specifically, large losses
in soil and biomass carbon pools in the last 150 years could have contributed significantly to observed increases in atmospheric
Hg pollution. The roles of vegetation and terrestrial carbon pools should receive detailed consideration on how they might
attenuate or exacerbate atmospheric Hg pollution. 相似文献
79.
Soil carbon saturation: concept,evidence and evaluation 总被引:20,自引:0,他引:20
Catherine E. Stewart Keith Paustian Richard T. Conant Alain F. Plante Johan Six 《Biogeochemistry》2007,86(1):19-31
Current estimates of soil C storage potential are based on models or factors that assume linearity between C input levels
and C stocks at steady-state, implying that SOC stocks could increase without limit as C input levels increase. However, some
soils show little or no increase in steady-state SOC stock with increasing C input levels suggesting that SOC can become saturated with respect to C input. We used long-term field experiment data to assess alternative hypotheses of soil carbon storage
by three simple models: a linear model (no saturation), a one-pool whole-soil C saturation model, and a two-pool mixed model
with C saturation of a single C pool, but not the whole soil. The one-pool C saturation model best fit the combined data from
14 sites, four individual sites were best-fit with the linear model, and no sites were best fit by the mixed model. These
results indicate that existing agricultural field experiments generally have too small a range in C input levels to show saturation
behavior, and verify the accepted linear relationship between soil C and C input used to model SOM dynamics. However, all
sites combined and the site with the widest range in C input levels were best fit with the C-saturation model. Nevertheless,
the same site produced distinct effective stabilization capacity curves rather than an absolute C saturation level. We conclude
that the saturation of soil C does occur and therefore the greatest efficiency in soil C sequestration will be in soils further
from C saturation.
相似文献
Catherine E. StewartEmail: |
80.
Pine plantations of the southeastern USA are regional carbon (C) sinks. In spite of large increases in woody biomass due to
advanced growing systems, studies have shown little or even negative effects on the C content of the extremely sandy soils
of this region. Hence, it is important to understand the mechanisms that determine the impact of intensive forest management
on soil organic carbon (SOC) sequestration. This study was conducted to examine the C profile in a 4-year-old loblolly pine
(Pinus taeda L.) plantation managed under two levels of management intensity (chemical understory control and fertilizer inputs). Soil
organic C and nitrogen (N) pools were evaluated using two size fractionation methods, dry and wet sieving (2000–250 μm, 250–150 μm,
150–53 μm and <53 μm). Dry sieving was preferred over wet sieving for soil size fractionation, as it preserved more structure
and water-soluble SOC components such as esters and amides and did not affect the N distribution. Diffuse Reflectance Infrared
Fourier Transform Spectroscopy (DRIFTS) spectra were used to examine the chemical composition of the size fractions, which
showed the presence of recently added organic matter in the largest sand fraction, as well as more decomposed organic matter
in the <53 μm fraction. Intensive forest management reduced SOC in all three 2000–53 μm fractions, most likely due to reduced
root input of understory plants that were controlled using herbicides. The 2000–250 μm fractions contained nearly half of
the total SOC and showed a 23% decrease in C content due to the intensive management regime. Results from this study indicated
the significance and responsiveness of sand size SOC fractions in Florida Spodosols. Results also showed that reductions in
SOC due to intensive management occurred after four years and highlighted the need to understand the long-term impacts and
the mechanisms responsible.
Responsible Editor: Barbara Wick 相似文献