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51.
长期在高浓度CO2环境下生长的植物往往会发生光合适应或下调,即在相同CO2浓度下的光合速率明显低于普通空气中生长的对照。虽然关于这种现象已经有许多研究报告和综述文章,但是它的机理还不很清楚。本文结合作者所在研究组的工作,概述了关于植物光合适应机理研究的新进展,提出除了呼吸作用增强和光合产物超常积累的可能作用以外,二磷酸核酮糖(RuBP)羧化限制和RuBP再生限制可能是导致植物光合适应的主要因素。 相似文献
52.
In comparison with its wild type (WT), the transgenic (TG) rice with silenced OsBP-73 gene had significantly lower plant height, grain number per panicle, and leaf net photosynthetic rate (P
N). Also, the TG rice showed significantly lower chlorophyll (Chl), ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBPCO),
RuBPCO activase, and RuBP contents, photosystem 2 (PS2) photochemical efficiency (Fv/Fm and ΔF/Fm′), apparent quantum yield of carbon assimilation (Φc), carboxylation efficiency (CE), photosynthetic electron transport and photophosphorylation rates as well as sucrose phosphate
synthase activity, but higher intercellular CO2 concentration, sucrose, fructose, and glycerate 3-phosphate contents, and non-photochemical quenching of Chl fluorescence
(NPQ). Thus the decreased P
N in the TG rice leaves is related to both RuBP carboxylation and RuBP regeneration limitations, and the latter is a predominant
limitation to photosynthesis. 相似文献
53.
Li Q Jiang Q Schurgers LJ Uitto J 《Biochemical and biophysical research communications》2007,364(2):208-213
Pseudoxanthoma elasticum (PXE), a heritable multi-system disorder manifesting with ectopic mineralization of soft connective tissues, is caused by mutations in the ABCC6/MRP6 gene/protein system, but the mechanisms how the ABCC6 mutations lead to aberrant mineralization are currently unknown. In this study, we utilized a transgenic mouse model, Abcc6−/−, to examine the mineralization processes. We focused on matrix gla protein (MGP) which has been shown to be critical, when activated by γ-carboxylation of glutamyl residues, for prevention of unwanted mineralization. The concentration of MGP in the serum of Abcc6−/− mice was significantly reduced when compared to wild-type controls (p < 0.004). More importantly, MGP isolated from the liver of Abcc6−/− mice was largely under-carboxylated and therefore possesses no activity. Finally, examination of the Abcc6−/− mice revealed association of total and under-carboxylated forms of MGP with ectopic mineralization while the γ-carboxylated form was essentially absent. These results suggest that MGP in Abcc6−/− mice is largely in inactive form and is unable to prevent the unwanted mineralization of connective tissues in PXE. 相似文献
54.
The relationship of leaf photosynthetic traits – Vcmax and Jmax – to leaf nitrogen,leaf phosphorus,and specific leaf area: a meta‐analysis and modeling study
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Anthony P. Walker Andrew P. Beckerman Lianhong Gu Jens Kattge Lucas A. Cernusak Tomas F. Domingues Joanna C. Scales Georg Wohlfahrt Stan D. Wullschleger F. Ian Woodward 《Ecology and evolution》2014,4(16):3218-3235
Great uncertainty exists in the global exchange of carbon between the atmosphere and the terrestrial biosphere. An important source of this uncertainty lies in the dependency of photosynthesis on the maximum rate of carboxylation (Vcmax) and the maximum rate of electron transport (Jmax). Understanding and making accurate prediction of C fluxes thus requires accurate characterization of these rates and their relationship with plant nutrient status over large geographic scales. Plant nutrient status is indicated by the traits: leaf nitrogen (N), leaf phosphorus (P), and specific leaf area (SLA). Correlations between Vcmax and Jmax and leaf nitrogen (N) are typically derived from local to global scales, while correlations with leaf phosphorus (P) and specific leaf area (SLA) have typically been derived at a local scale. Thus, there is no global-scale relationship between Vcmax and Jmax and P or SLA limiting the ability of global-scale carbon flux models do not account for P or SLA. We gathered published data from 24 studies to reveal global relationships of Vcmax and Jmax with leaf N, P, and SLA. Vcmax was strongly related to leaf N, and increasing leaf P substantially increased the sensitivity of Vcmax to leaf N. Jmax was strongly related to Vcmax, and neither leaf N, P, or SLA had a substantial impact on the relationship. Although more data are needed to expand the applicability of the relationship, we show leaf P is a globally important determinant of photosynthetic rates. In a model of photosynthesis, we showed that at high leaf N (3 gm−2), increasing leaf P from 0.05 to 0.22 gm−2 nearly doubled assimilation rates. Finally, we show that plants may employ a conservative strategy of Jmax to Vcmax coordination that restricts photoinhibition when carboxylation is limiting at the expense of maximizing photosynthetic rates when light is limiting. 相似文献
55.
Sebastian Carballal Victor Vitvitsky Roshan Kumar David A. Hanna Marouane Libiad Aditi Gupta Jace W. Jones Ruma Banerjee 《The Journal of biological chemistry》2021,297(2)
Mammalian cells synthesize H2S from sulfur-containing amino acids and are also exposed to exogenous sources of this signaling molecule, notably from gut microbes. As an inhibitor of complex IV in the electron transport chain, H2S can have a profound impact on metabolism, suggesting the hypothesis that metabolic reprogramming is a primary mechanism by which H2S signals. In this study, we report that H2S increases lipogenesis in many cell types, using carbon derived from glutamine rather than from glucose. H2S-stimulated lipid synthesis is sensitive to the mitochondrial NAD(P)H pools and is enabled by reductive carboxylation of α-ketoglutarate. Lipidomics analysis revealed that H2S elicits time-dependent changes across several lipid classes, e.g., upregulating triglycerides while downregulating phosphatidylcholine. Direct analysis of triglyceride concentration revealed that H2S induces a net increase in the size of this lipid pool. These results provide a mechanistic framework for understanding the effects of H2S on increasing lipid droplets in adipocytes and population studies that have pointed to a positive correlation between cysteine (a substrate for H2S synthesis) and fat mass. 相似文献
56.
Photosynthetic CO2 fixation is the ultimate source of organic carbon on earth and thus is essential for crop production and carbon sequestration. Ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) catalyzes the first step of photosynthetic CO2 fixation. However, the extreme low carboxylation efficiency of Rubisco makes it the most attractive target for improving photosynthetic efficiency. Extensive studies have focused on re-engineering a more efficient enzyme, but the effort has been impeded by the limited understanding of its structure-function relationships and the lack of an efficient selection system towards its activity. To address the unsuccessful molecular engineering of Rubisco, we developed an Escherichia coli-based activity-directed selection system which links the growth of host cell solely to the Rubisco activity therein. A Synechococcus sp. PCC7002 Rubisco mutant with E49V and D82G substitutions in the small subunit was selected from a total of 15,000 mutants by one round of evolution. This mutant showed an 85% increase in specific carboxylation activity and a 45% improvement in catalytic efficiency towards CO2. The small-subunit E49V mutation was speculated to influence holoenzyme catalysis through interaction with the large-subunit Q225. This interaction is conserved among various Rubisco from higher plants and Chlamydomonas reinhardtii. Knowledge of these might provide clues for engineering Rubisco from higher plants, with the potential of increasing the crop yield. 相似文献
57.
Responses of photosynthetic parameters of Quercus mongolica to soil moisture stresses 总被引:1,自引:0,他引:1
The effect of drought on plant photosynthetic parameters has not been quantitatively described in the models of plant photosynthetic mechanism, so the seedlings of Quercus mongolica from Northeast China were used to study the responses of the photosynthetic parameters to soil water stresses. The results showed that the relationship between the maximum net leaf photosynthetic rate (Pmax) of Quercus mongolica and soil moisture could be expressed as a quadratic curve (P < 0.01), and Pmax reached the maximum when soil volume moisture was close to 35.45% of the field water holding capacity. The maximum rate of carboxylation (Vcmax), the maximum potential rate of electron transport (Jmax) and triose phosphate utilization (TPU) rate of Quercus mongolica also had quadratic relationships with soil water content (P < 0.01). Namely, Vcmax, Jmax and TPU had similar response curves to soil water, but had different optimal soil water contents. Based on the temperature and responses of plant photosynthetic parameters to water, this function provides researchers with the parameters and methodology for understanding and simulating the responses of plant photosynthetic parameters to drought stress. 相似文献
58.
To understand the ecophysiological adaptation of Lilium “Oriental Hybrids”, which are grown for their commercial bulbs, the
gas exchange, leaf N and chlorophyll content of the three varieties were investigated in the central areas of the Yunnan Province.
Among the three varieties, light-saturated photosynthetic rate at ambient CO2 (Amax) of Tiber was the highest, while that of Siberia was the lowest. The difference in the Amax was related to the carboxylation efficiency (CE), leaf mass per unit area and leaf N content per mass, which indicated that
their photosynthetic capacity was influenced by the activity and/or the quantity of Rubisco. The three varieties had lower
photosynthetic saturation points and photosynthetic compensation points, but the photosynthetic rates were not decreased up
to 2000 μmol·m−2·s−1 of the light intensity. This indicates that the three varieties had broad adaptability to light intensity. There were significant
differences in the photosynthetic optimum temperature among the three varieties. Siberia had the highest photosynthetic optimum
temperature (25.5°C–34.9°C), and is likely to grow well in warm areas. Sorbonne had the lowest photosynthetic optimum temperature
(19.3°C–25.6°C), and its growth is favored in cool areas. Tiber can maintain a high photosynthetic rate within a wide range
of temperature. Therefore, Tiber is the most suitable variety for the climate in the central areas of the Yunnan Province,
China.
__________
Translated from Acta Botanica Yunnanica, 2007, 29(1): 1–6 [译自:云南植物研究] 相似文献
59.
Maseyk KS Lin T Rotenberg E Grünzweig JM Schwartz A Yakir D 《The New phytologist》2008,178(3):603-616
This study explored possible advantages conferred by the phase shift between leaf phenology and photosynthesis seasonality in a semi-arid Pinus halepensis forest system, not seen in temperate sites. Leaf-scale measurements of gas exchange, nitrogen and phenology were used on daily, seasonal and annual time-scales. Peak photosynthesis was in late winter, when high soil moisture, mild temperatures and low leaf vapour pressure deficit (D(L)) allowed high rates associated with high water- and nitrogen-use efficiencies. Self-sustained new needle growth through the dry and hot summer maximized photosynthesis in the following wet season, without straining carbon storage. Low rates of water loss were associated with increasing sensitivity of stomatal conductance (g(s)) to soil moisture below a relative extractable water (REW) of 0.4, and decreased g(s )sensitivity to D(L) below REW of approx. 0.2. This response was captured by the modified Ball-Berry (Leuning) model. While most physiological parameters and responses measured were typical of temperate pines, the photosynthesis-phenological phasing contributed to high productivity under warm-dry conditions. This contrasts with reported effects of short-term periodical droughts and could lead to different predictions of the effect of warming and drying climate on pine forest productivity. 相似文献
60.