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1.
Y. Kitaya L. Xiao A. Masuda T. Ozawa M. Tsuda K. Omasa 《Journal of applied phycology》2008,20(5):737-742
Symbiotic dinoflagellates of the species Amphidinium are expected to be pharmaceutically useful microalgae because they produce antitumor macrolides. A microalgae production
system with a large number of cells at a high density has been developed for the efficient production of macrolide compounds.
In the present study, the effects of culture conditions on the cellular growth rate of dinoflagellates were investigated to
determine the optimum culture conditions for obtaining high yields of microalgae. Amphidinium species was cultured under conditions with six temperature levels (21–35°C), six levels of photosynthetic photon flux density
(15–70 μmol photons m−2 s−1), three levels of CO2 concentration (0.02–0.1%), and three levels of O2 concentration (0.2–21%). The number of cells cultured in a certain volume of solution was monitored microscopically and the
cellular growth rate was expressed as the specific growth rate. The maximum specific growth rate was 0.022 h−1 at a temperature of 26°C and O2 concentration of 5%, and the specific growth rate was saturated at a CO2 concentration of 0.05%, a photosynthetic photon flux density of 35 μmol photons m−2 s−1 and a photoperiod of 12 h day−1 upon increasing each environmental parameter. The results demonstrate that Amphidinium species can multiply efficiently under conditions of relatively low light intensity and low O2 concentration. 相似文献
2.
The objective of this study was to improve the biological water–gas shift reaction for producing hydrogen (H2) by conversion of carbon monoxide (CO) using an anaerobic thermophilic pure strain, Carboxydothermus hydrogenoformans. Specific hydrogen production rates and yields were investigated at initial biomass densities varying from 5 to 20 mg volatile
suspended solid (VSS) L−1. Results showed that the gas–liquid mass transfer limits the CO conversion rate at high biomass concentrations. At 100-rpm
agitation and at CO partial pressure of 1 atm, the optimal substrate/biomass ratio must exceed 5 mol CO g−1 biomass VSS in order to avoid gas–liquid substrate transfer limitation. An average H2 yield of 94 ± 3% and a specific hydrogen production rate of ca. 3 mol g−1 VSS day−1 were obtained at initial biomass densities between 5 and 8 mg VSS−1. In addition, CO bioconversion kinetics was assessed at CO partial pressure from 0.16 to 2 atm, corresponding to a dissolved
CO concentration at 70°C from 0.09 to 1.1 mM. Specific bioactivity was maximal at 3.5 mol CO g−1 VSS day−1 for a dissolved CO concentration of 0.55 mM in the culture. This optimal concentration is higher than with most other hydrogenogenic
carboxydotrophic species. 相似文献
3.
The impact of altitudinal gradients on the performance of alder–cardamom agroforestry systems was analyzed on nitrogenase
activity, N2-fixation efficiency, and stand energetics and efficiencies in the eastern Himalayas. Acetylene reduction (AR activity) measurements
showed that nitrogenase activity considerably increased with advancing altitudes from 500 to 800 m to a peak at 900–1,200 m.
AR activity was fairly high, between 1,300 and 1,700 m, and sharply decreased in the stands between 1,800 and 2,100 m. AR
activity increased in the growing season and peaked in the rainy season. This significantly coincided with cardamom flowering
during the onset of growing season to full fruiting stage at peak activity period. AR activity was dependent on soil temperature
and moisture and showed a positive relationship. Nodule moisture was also a limiting factor for AR activity and showed a positive
correlation. Diurnal changes showed a marked variation with highest AR activity between 8 and 12 h. The performance of commercial
cardamom crop is dependent on the associated shade trees. Yield potential significantly coincided with the rate of N2-fixation both at age chronosequence and altitudinal gradients. The management comprises growing large number of alder until
10 years and thinning, and gap filling of cardamom up to 20 years. Such maintenance caused non-equilibrium conditions that
favored systems efficiency and excellent production until 20 years. System efficiency sharply declined at low rates of N2-fixation, AR activity, root nodule production, and agronomic yield due to the influence of stand age and altitudinal gradients.
Agroforestry stands at 900–1,700 m were more energy cost-effective due to the lower energy required for per-kg N-fixation
with high N supply (115–155 kg ha−1) confirming functionally efficient than those stands at extreme higher and lower altitudinal ranges. Therefore, replantation
of alder and cardamom and phase wise agroforestry rotation after 20 years could be an ecologically and economically sustainable
management practice. 相似文献
4.
Hong-Ling Cui Ji-Jun Zhao Feng Zhao Xiang-Rong Chen Qing-Ming Zhang 《Molecular simulation》2013,39(9):670-681
Using first-principles density functional theory and classical molecular dynamics (MD), the structural, electronic and mechanical properties of the energetic material β-HMX have been studied. The crystal structure optimised by the local density approximation calculations compares reasonably with the experimental data. Electronic band structure and density of states indicate that β-HMX is an insulator with a band gap of 3.059 eV. The pressure effect on the crystal structure and physical properties has been investigated in the range of 0–40 GPa. The crystal structure and electronic properties change slightly as the pressure increases from 0 to 2.5 GPa; when the pressure is above 2.5 GPa, further increment of the pressure results in significant changes in crystal structure. There is a larger compression along the b-axis than along the a- and c-axes. Isothermal–isobaric MD simulations on β-HMX were performed in the temperature range of 5–400 K. Phase transition at 360 K, corresponding to a volume interrupt, was found. The computed thermal expansion coefficients show anisotropic behaviour with a slightly larger expansion along the b- and c-axes than along the a-axis. In the temperature range of 5–360 K, β-HMX possesses good plasticity and its stiffness decreases with increasing the temperature. 相似文献
5.
In2O3 nanoparticle-assembled nanorods with distinct surface morphologies have been newly synthesized by a dehydration process of
self-assembled In(OH)3 nanorods obtained from a liquid-based route. The reaction mechanism and the structural transformation between these two one-dimensional
nanorods, In2O3 and In(OH)3, were precisely characterized by means of various qualitative and quantitative analyses with X-ray scattering simulations.
The broad absorption band in the UV–visible spectrum evidently originates from the nanoparticle-assembling effect within the
In2O3 nanorods. An intensive photoluminescence emission at 440 nm observed under an excitation wavelength of 325 nm is attributed
to the existence of oxygen vacancies within the In2O3 nanorods. 相似文献
6.
Christian Brümmer Nicolas Brüggemann Klaus Butterbach-Bahl Ulrike Falk Jörg Szarzynski Konrad Vielhauer Reiner Wassmann Hans Papen 《Ecosystems》2008,11(4):582-600
In a combined field and laboratory study in the southwest of Burkina Faso, we quantified soil-atmosphere N2O and NO exchange. N2O emissions were measured during two field campaigns throughout the growing seasons 2005 and 2006 at five different experimental
sites, that is, a natural savanna site and four agricultural sites planted with sorghum (n = 2), cotton and peanut. The agricultural fields were not irrigated and not fertilized. Although N2O exchange mostly fluctuated between −2 and 8 μg N2O–N m−2 h−1, peak N2O emissions of 10–35 μg N2O–N m−2 h−1 during the second half of June 2005, and up to 150 μg N2O–N m−2 h−1 at the onset of the rainy season 2006, were observed at the native savanna site, whereas the effect of the first rain event
on N2O emissions at the crop sites was low or even not detectable. Additionally, a fertilizer experiment was conducted at a sorghum
field that was divided into three plots receiving different amounts of N fertilizer (plot A: 140 kg N ha−1; plot B: 52.5 kg N ha−1; plot C: control). During the first 3 weeks after fertilization, only a minor increase in N2O emissions at the two fertilized plots was detected. After 24 days, however, N2O emission rates increased exponentially at plot A up to a mean of 80 μg N2O–N m−2 h−1, whereas daily mean values at plot B reached only 19 μg N2O–N m−2 h−1, whereas N2O flux rates at plot C remained unchanged. The calculated annual N2O emission of the nature reserve site amounted to 0.52 kg N2O–N ha−1 a−1 in 2005 and to 0.67 kg N2O–N ha−1 a−1 in 2006, whereas the calculated average annual N2O release of the crop sites was only 0.19 kg N2O–N ha−1 a−1 and 0.20 kg N2O–N ha−1 a−1 in 2005 and 2006, respectively. In a laboratory study, potential N2O and NO formation under different soil moisture regimes were determined. Single wetting of dry soil to medium soil water
content with subsequent drying caused the highest increase in N2O and NO emissions with maximum fluxes occurring 1 day after wetting. The stimulating effect lasted for 3–4 days. A weaker
stimulation of N2O and NO fluxes was detected during daily wetting of soil to medium water content, whereas no significant stimulating effect
of single or daily wetting to high soil water content (>67% WHCmax) was observed. This study demonstrates that the impact of land-use change in West African savanna on N trace gas emissions
is smaller—with the caveat that there could have been potentially higher N2O and NO emissions during the initial conversion—than the effect of timing and distribution of rainfall and of the likely
increase in nitrogen fertilization in the future. 相似文献
7.
A series of N4X (X = O, S, Se) compounds have been examined with ab initio and density functional theory (DFT) methods. To our knowledge,
these compounds, except for the C2v ring and the C3v towerlike isomers of N4O, are first reported here. The ring structures are the most energetically favored for N4X (X = O and S) systems. For N4Se, the cagelike structure is the most energetically favored. Several decomposition and isomerization pathways for the N4X species have been investigated. The dissociation of C2v ring N4O and N4S structures via ring breaking and the barrier height are only 1.1 and −0.2 kcal mol−1 at the CCSD(T)/6-311+G*//MP2/6-311+G* level of theory. The dissociation of the cagelike N4X species is at a cost of 12.1–16.2 kcal mol−1. As for the towerlike and triangle bipyramidal isomers, their decomposition or isomerization barrier heights are all lower
than 10.0 kcal mol−1. Although the CS cagelike N4S isomer has a moderate isomerization barrier (18.3–29.1 kcal mol−1), the low dissociation barrier (−1.0 kcal mol−1) indicates that it will disappear when going to the higher CCSD(T) level.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
8.
A horizontal biotrickling filter (HBTF) was used to inoculate autotrophic sulfide-oxidizing and ammonia-oxidizing microbial
consortiums over H2S-exhausted carbon for co-treating H2S and NH3 waste gas in a long-term operation. In this study, several aspects (i.e., pH change, shock loading and starvation) of the
dynamic behavior of the HBTF were investigated. The metabolic products of N and S bearing species in recycling liquid and
biological activities of the biofilm were analyzed to explain the observed phenomena and further explore the fundamentals
behind. In the pH range of 4–8.5, although the removal efficiencies of H2S and NH3 remained 96–98% and 100%, respectively, the metabolic products demonstrated different removal mechanisms and pathways. NH4-N and NO2/NO3-N were dominated at pH ≤6 and ≥7, respectively, indicating the differentiated contributions from physical/chemical adsorption
and bio-oxidation. Moreover, the HBTF demonstrated a good dynamic stability to withstand shock loadings by recovering immediately
to the original. During shock loading, only 15.4% and 17.9% of captured H2S and NH3 was biodegraded, respectively. After 2, 11, and 48 days of starvation, the HBTF system reached a full performance within
reasonable re-startup times (2–80 h), possibly due to the consumption of reduced S and N species in biomass or activated carbon
thus converted into SO4-S and NO3-N during starvation period. The results helped to understand the fundamental knowledge by revealing the effects of pH and
transient loadings linked with individual removal mechanism for H2S and NH3 co-treatment in different conditions. 相似文献
9.
Zoccarato F Miotto C Cavallini L Alexandre A 《Journal of bioenergetics and biomembranes》2011,43(4):359-366
In brain mitochondria succinate activates H2O2 release, concentration dependently (starting at 15 μM), and in the presence of NAD dependent substrates (glutamate, pyruvate,
β-hydroxybutyrate). We report that TCA cycle metabolites (citrate, isocitrate, α-ketoglutarate, fumarate, malate) individually
and quickly inhibit H2O2 release. When they are present together at physiological concentration (0.2, 0.01, 0.15, 0.12, 0.2 mM respectively) they
decrease H2O2 production by over 60% at 0.1–0.2 mM succinate. The degree of inhibition depends on the concentration of each metabolite.
Acetoacetate is a strong inhibitor of H2O2 release, starting at 10 μM and acting quickly. It potentiates the inhibition induced by TCA cycle metabolites. The action
of acetoacetate is partially removed by β-hydroxybutyrate. Removal is minimal at 0.1 mM acetoacetate, and is higher at 0.5 mM
acetoacetate. We conclude that several inhibitors of H2O2 release act jointly and concentration dependently to rapidly set the required level of H2O2 generation at each succinate concentration. 相似文献
10.
Min Zhao Christopher J. Destache Sunny E. Ohia Catherine A. Opere 《Neurochemical research》2009,34(12):2170-2180
The role of enzymes and receptors of the prostanoid pathway in the inhibitory effect of 8-isoprostaglandin E2 (8-isoPGE2) on endogenous amino acid neurotransmitter levels was examined, ex vivo. Freshly isolated bovine eyeballs were injected intravitreally
with IsoPs, incubated in Krebs buffer for 30 min and retina prepared for HPLC-ECD detection of amino acids. 8-isoPGE2 attenuated retinal glutamate and its metabolite, glutamine and glycine in a concentration-dependent manner. The non-selective
cyclooxygenase (COX)-inhibitor, flurbiprofen, COX-2 selective inhibitor, NS-398 and thromboxane (Tx) synthase inhibitor, furegrelate
had no effect on both basal amino acid levels and the inhibitory effects of 8-isoPGE2 (1–100 μM) on the retinal amino acids. Whereas the TP-receptor antagonist SQ-29548(10 μM) exhibited no effect, SC-19220(EP1; 30 μM), AH-6809(EP1–3; 30 μM) and AH-23848(EP4; 30 μM) reversed the inhibitory effects of 8-isoPGE2 (0.01–100 μM) on glutamate, glutamine and glycine levels. We conclude that prostanoid EP-receptors regulate the inhibitory
effect of 8-isoPGE2 on basal levels of endogenous amino acids in bovine retina, ex vivo. 相似文献
11.
Niels Thomas Eriksen Frederik Kier Riisgård William Stuart Gunther Jens Jørgen Lønsmann Iversen 《Journal of applied phycology》2007,19(2):161-174
Growth of the green algae Chlamydomonas reinhardtii and Chlorella sp. in batch cultures was investigated in a novel gas-tight photobioreactor, in which CO2, H2, and N2 were titrated into the gas phase to control medium pH, dissolved oxygen partial pressure, and headspace pressure, respectively.
The exit gas from the reactor was circulated through a loop of tubing and re-introduced into the culture. CO2 uptake was estimated from the addition of CO2 as acidic titrant and O2 evolution was estimated from titration by H2, which was used to reduce O2 over a Pd catalyst. The photosynthetic quotient, PQ, was estimated as the ratio between O2 evolution and CO2 up-take rates. NH4
+, NO2
−, or NO3
− was the final cell density limiting nutrient. Cultures of both algae were, in general, characterised by a nitrogen sufficient
growth phase followed by a nitrogen depleted phase in which starch was the major product. The estimated PQ values were dependent on the level of oxidation of the nitrogen source. The PQ was 1 with NH4
+ as the nitrogen source and 1.3 when NO3
− was the nitrogen source. In cultures grown on all nitrogen sources, the PQ value approached 1 when the nitrogen source was depleted and starch synthesis became dominant, to further increase towards
1.3 over a period of 3–4 days. This latter increase in PQ, which was indicative of production of reduced compounds like lipids, correlated with a simultaneous increase in the degree
of reduction of the biomass. When using the titrations of CO2 and H2 into the reactor headspace to estimate the up-take of CO2, the production of O2, and the PQ, the rate of biomass production could be followed, the stoichiometrical composition of the produced algal biomass could be
estimated, and different growth phases could be identified. 相似文献
12.
Fanyan Meng Chuanlai Shen Fengqin Miao Yong He Yuqing Shen Wei Xie Jianqiong Zhang 《Biotechnology letters》2010,32(12):1803-1808
The heavy chain protein of HLA-peptide complexes (HLA/HBc18–27 and HLA/CEA694–702) immobilized onto an ion exchange chromatography column and then the dilution-refolded HBc18–27-fused or CEA694–702-fused β2m protein was able to pass through the column. Using this method, HLA/peptide complexes were prepared within 30 h
with a refolding yield of at least 20% (w/w) and purity of over 80% (w/w). This strategy refolds, concentrates, and purifies
HLA/peptide complexes in a single integrated step and offers a potential tool to refold multiple-subunit proteins other than
the major histocompatibility complex (MHC)/peptide complexes. 相似文献
13.
A survey was carried out to detect the presence of aflatoxin B1 in 60 duplicated samples (120 samples) of peanuts butter purchased from the local markets and other traditionally prepared
and distributed by the street sellers in Khartoum state, Sudan. AflaTest-P affinity column was used to extract the toxin from
the samples, and the concentration was measured by calibrated Vicam fluorometer. Aflatoxin B1 was detected at variable levels in 100% of the screened samples. Traditionally prepared samples showed the highest incidence
of aflatoxin B1 which is above the internationally regulated tolerance levels (5–20 ppb). The means and the ranges of the aflatoxin B1 recovered were as follows: 63.9 ppb (29–128 ppb), 54.5 ppb (21–131 ppb) and 101 ppb (17–170 ppb) for samples collected from
Khartoum, Khartoum North and Omdurman areas, respectively. Samples from retail stores presented relatively low aflatoxin B1 incidences 14.5 ppb (1–57 ppb), but only 30% of the samples revealed aflatoxin level below 10 ppb. Laboratory segregated
and carefully prepared butter from good grade nuts showed the lowest levels of this toxin (3.3 ppb; 2–6 ppb). The results
showed that peanuts butter prepared by the street sellers and distributed by the retail stores are evidently hazardous to
human health. There is therefore urgent need for strong form of quality control measures and public awareness. The use of
excellent grade peanuts and care during processing and storage are priority. 相似文献
14.
Gonzalo Sánchez Natalia Colettis Pablo Vázquez Carlos Cerveñansky Alejandra Aguirre Jorge A. Quillfeldt Diana Jerusalinsky Edgar Kornisiuk 《Neurochemical research》2009,34(8):1363-1371
The five muscarinic acetylcholine receptors (M1–M5) are differentially expressed in the brain. M2 and M4 are coupled to inhibition of stimulated adenylyl cyclase, while M1, M3 and M5 are mainly coupled to the phosphoinositide pathway. We studied the muscarinic receptor regulation of adenylyl cyclase activity
in the rat hippocampus, compared to the striatum and amygdala. Basal and forskolin-stimulated adenylyl cyclase activity was
higher in the striatum but the muscarinic inhibition was much lower. Highly selective muscarinic toxins MT1 and MT2—affinity
order M1 ≥ M4 >> others—and MT3—highly selective M4 antagonist—did not show significant effects on basal or forskolin-stimulated cyclic AMP production but, like scopolamine,
counteracted oxotremorine inhibition. Since MTs have negligible affinity for M2, M4 would be the main subtype responsible for muscarinic inhibition of forskolin-stimulated enzyme. Dopamine stimulated a small
fraction of the enzyme (3.1% in striatum, 1.3% in the hippocampus). Since MT3 fully blocked muscarinic inhibition of dopamine-stimulated
enzyme, M4 receptor would be responsible for this regulation.
Diana Jerusalinsky and Edgar Kornisiuk contributed equally to this paper. 相似文献
15.
Methods to determine zearalenone (ZEA), deoxynivalenol (DON), aflatoxins (AF) and their metabolites in pig urine were developed
as biomarkers for pig exposure to the mycotoxins in feed. Urine samples were incubated with β-glucuronidase to cleave conjugates,
extracted and cleaned-up with solid phase and immunoaffinity columns, followed by HPLC with UV and fluorescence detection.
Good recoveries (83–130%), low variation (2–10%), and low detection limits (0.3–9.9 ng/ml) were obtained. The results of controlled
AFB1 feeding trials found no difference in urine concentrations of AFB1 or AFM1 from pigs fed three different levels (127, 227, 327 μg/kg) of AFB1 in diets. The excretion of AFB1 and AFM1 in urine was on average 30% of the oral dose and the ratio AFB1 to AFM1 was around 23%. The analysis of 15 Vietnamese pig urine samples indicate a relatively high exposure of ZEA, DON and AF, which
were found as toxin or metabolites in 47, 73, and 80% of the urine samples, respectively. 相似文献
16.
Parkinson’s disease (PD) is a progressive neurodegenerative disorder with a prevalence of 1–2% in people over the age of 50.
Mitochondrial dysfunction occurred in PD patients showing a 15–30% loss of activity in complex I. Asiatic acid (AA), a triterpenoid,
is an antioxidant and used for depression treatment, but the effect of AA against PD-like damage has never been reported.
In the present study, we investigated the protective effects of AA against H2O2 or rotenone-induced cellular injury and mitochondrial dysfunction in SH-SY5Y cells. Mitochondrial membrane potential (MMP)
and the expression of voltage-dependent anion channel (VDAC) were detected with or without AA pretreatment following cellular
injury to address the possible mechanisms of AA neuroprotection. The results showed that pre-treatment of AA (0.01–100 nM)
protected cells against the toxicity induced by rotenone or H2O2. In addition, MMP dissipation occurred following the exposure of rotenone, which could be prevented by AA treatment. More
interestingly, pre-administration of AA inhibited the elevation of VDAC mRNA and protein levels induced by rotenone(100 nM)
or H2O2 (300 μM).These data indicate that AA could protect neuronal cells against mitochondrial dysfunctional injury and suggest
that AA might be developed as an agent for PD prevention or therapy.
Special issue article in honor of Dr. Akitane Mori. 相似文献
17.
Alptekin S 《Journal of molecular modeling》2012,18(3):1167-1172
A constant pressure ab initio MD technique and density functional theory with a generalized gradient approximation (GGA) was
used to study the pressure-induced phase transition in wurtzite ZnTe. A first-order phase transition from the wurtzite structure
to a Cmcm structure was successfully observed in a constant-pressure molecular dynamics simulation. This phase transformation was also
analyzed using enthalpy calculations. We also investigated the stability of wurtzite (WZ) and zinc-blende (ZB) phases from
energy–volume calculations, and found that both structures show quite similar equations of state and transform into a Cmcm structure at 16 GPa using enthalpy calculations, in agreement with experimental observations. The transition phase, lattice
parameters and bulk properties we obtained are comparable with experimental and theoretical data. 相似文献
18.
Sarra El Ichi Anna Miodek Hélène Sauriat-Dorizon Jean-Pierre Mahy Céline Henry Mohamed Nejib Marzouki Hafsa Korri-Youssoufi 《Journal of biological inorganic chemistry》2011,16(1):157-172
Structural characterization and study of the activity of new POX1B protein from garlic which has a high peroxidase activity and can be used as a biosensor for the detection of hydrogen peroxide
and phenolic compounds were performed and compared with the findings for other heme peroxidases. The structure–function relationship
was investigated by analysis of the spectroscopic properties and correlated to the structure determined by a new generation
of high-performance hybrid mass spectrometers. The reactivity of the enzyme was analyzed by studies of the redox activity
toward various ligands and the reactivity with various substrates. We demonstrated that, in the case of garlic peroxidase,
the heme group is pentacoordinated, and has an histidine as a proximal ligand. POX1B exhibited a high affinity for hydrogen peroxide as well as various reducing cosubstrates. In addition, high enzyme specificity
was demonstrated. The k
cat and K
M values were 411 and 400 mM−1 s−1 for 3,3′,5,5′-tetramethylbenzidine and 2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid), respectively. Furthermore, the
reduction of nitro compounds in the presence of POX1B was demonstrated by iron(II) nitrosoalkane complex assay. In addition, POX1B showed a great potential for application for drug metabolism since its ability to react with 1-nitrohexane in the presence
of sodium dithionite was demonstrated by the appearance of a characteristic Soret band at 411 nm. The high catalytic efficiency
obtained in the case of the new garlic peroxidase (POX1B) is suitable for the monitoring of different analytes and biocatalysis. 相似文献
19.
Oxygen tensions and osmotic potentials are important physiological factors of plant growth and development. To optimize these
variables for cotton (Gossypium hirsutum L.) embryo culture, we quantified dissolved O2 (dO2) tensions, osmotic potentials, and pH at several locations in cotton ovules during embryony. Clark O2 microelectrodes were micromanipulated into intact ovules at an angle lateral to the developing embryo, and dO2 tensions were determined in integuments, nucelli and embryos. Ovular osmotic potentials and pH were determined from extracted
ovule sap using vapor pressure osmometers and pH microelectrodes. Dissolved O2 tensions near or in embryos decreased from 104 mmol m−3 at 5 days post-anthesis (DPA) to 83 mmol m−3 at 18 DPA. Osmotic potentials of ovule sap decreased from −0.70 megapascals (MPa) at 2 DPA to −1.12 MPa at 8 DPA but then
increased to −0.84 MPa by 17 DPA. Ovule sap pH at 5–17 DPA varied inconsistently and ranged from 5.4 to 6.5. Based on these
results, a factorial experiment with two osmotic and three O2 treatments was designed. Immature embryos of cotton cultivar HS-26 were randomly assigned to the treatment combinations and
cultured for 33 days. Oxygen treatments did not affect embryo growth, and there were no differences among treatments with
regard to percentage of embryos that progressed to a more advanced stage of embryo development. However, cotyledons of embryos
grown without osmotic adjustment were abnormally large, and embryos exposed to these treatments were abnormally brown. Browning
was less severe for embryos exposed to low O2 tensions. Growth and pigmentation were most normal for embryos simultaneously exposed to O2 tensions and osmotic potentials that best simulated the observed in ovulo conditions. 相似文献
20.
Pilar Pérez Aitor Alonso Gloria Zita Rosa Morcuende Rafael Martínez-Carrasco 《Plant Growth Regulation》2011,65(3):439-447
Increases in growth temperature have been observed to affect photosynthesis differently under long-term exposure to ambient-
and twice ambient-air CO2 concentrations. This study investigates the causes of this interaction in wheat (Triticum aestivum L.) grown in the field over two consecutive years under temperature gradient chambers in ambient (370 μmol mol−1) or elevated (700 μmol mol−1) atmospheric CO2 concentrations and at ambient or ambient +4°C temperatures, with either a low or a high nitrogen supply. The photosynthesis-internal
CO2 response curves and the activity, activation state, kcat and amount of Ribulose-1, 5-bisphosphate carboxylase/oxygenase (Rubisco) were measured, as well as the soluble protein concentration
in flag leaves at ear emergence and 8–15 days after anthesis. A high nitrogen supply increased Vcmax, the Rubisco amount and activity and soluble protein contents, but did not significantly change the Rubisco kcat. Both elevated CO2 and above ambient temperatures had negative effects on Vcmax and Rubisco activity, but at elevated CO2, an increase in temperature did not decrease Vcmax or Rubisco activity in relation to ambient temperature. The amounts of Rubisco and soluble protein decreased with elevated
CO2 and temperature. The negative impact of elevated CO2 on Rubisco properties was somewhat counteracted at elevated temperatures by an increase in kcat. This effect can diminish the detrimental effects on photosynthesis of combined increases of CO2 and temperature. 相似文献