Interactions of Elevated CO2 Concentration and Drought Stress on Photosynthesis in Eucalyptus Cladocalyx F. Muell

Response of net photosynthetic rate (P _N), stomatal conductance (g _s), intercellular CO₂ concentration (c _i), and photosynthetic efficiency (F_v/F_m) of photosystem 2 (PS2) was assessed in Eucalyptus cladocalyx grown for long duration at 800 (C₈₀₀) or 380 (C₃₈₀) μmol mol^-1 CO₂ concentration under sufficient water supply or under water stress. The well-watered plants at C₈₀₀ showed a 2.2 fold enhancement of P _N without any change in g _s. Under both C₈₀₀ and C₃₈₀, water stress decreased P _N and g _s significantly without any substantial reduction of c _i, suggesting that both stomatal and non-stomatal factors regulated P _N. However, the photosynthetic efficiency of PS2 was not altered. This revised version was published online in June 2006 with corrections to the Cover Date.     

不同CO2浓度升高和氮肥水平对水稻叶绿素荧光特性的影响

为研究不同CO₂浓度升高和氮肥水平对水稻叶绿素荧光特性的影响,利用由开顶式气室（OTC）组成的CO₂浓度自动调控平台开展田间试验。以粳稻9108为试验材料,CO₂浓度设置CK（对照,环境大气CO₂浓度）、C₁（CO₂浓度比CK增加160 μmol/mol）和C₂（CO₂浓度比CK增加200 μmol/mol）3个水平;氮肥设置低氮（N₁：10 g/m²）、中氮（N₂：20 g/m²）和高氮（N₃：30 g/m²）3个水平。结果表明,在低氮条件下,与CK相比,C₁处理使拔节期的F_o上升4.8%（P=0.031）;C₂处理使拔节期的F_o上升6.3%（P=0.015）,F_v/F_m下降4.8%（P=0.003）,使孕穗期的F_o上升12.7%（P=0.039）,F_v/F_o下降18.2%（P=0.039）。在高氮条件下,与CK相比,C₂处理使灌浆期的F_m、F_v和F_v/F_m分别下降3.6%（P=0.039）、4.9%（P=0.013）和1.3%（P=0.039）。在中氮条件下,与CK相比,C₁和C₂处理的影响不明显。在整个生育期内,CO₂浓度升高与施氮处理交互作用对水稻叶绿素荧光特性的影响未到达显著水平。研究表明,大气CO₂浓度升高使水稻叶片光系统Ⅱ受损,抑制其电子传递能力、电子受体Q_A氧化还原情况、最大光化学效率和潜在活性,通过适量施氮可以有效地缓解其负面效应。     

What is the usual internal carbon dioxide concentration in C<Subscript>4</Subscript> species under midday field conditions?

The carbon dioxide concentrating system in C₄ photosynthesis allows high net photosynthetic rates (P _N) at low internal carbon dioxide concentrations (C _i), permitting higher P _N relative to stomatal conductance (g _s) than in C₃ plants. This relation would be reflected in the ratio of C _i to external ambient (C _a) carbon dioxide concentration, which is often given as 0.3 or 0.4 for C₄ plants. For a C _a of 360 μmol mol⁻¹ that would mean a C _i about 110–140 μmol mol⁻¹. Our field observations made near midday on three weedy C₄ species, Amaranthus retroflexus, Echinochloa crus-galli, and Setaria faberi, and the C₄ crop Sorghum bicolor indicated mean values of C _i of 183–212 μ mol mol⁻¹ at C _a = 360 μmol mol⁻¹. Measurements in two other C₄ crop species grown with three levels of N fertilizer indicated that while midday values of C _i at high photon flux were higher at limiting N, even at high nitrogen C _i averaged 212 and 196 μmol mol⁻¹ for Amaranthus hypochondriacus and Zea mays, respectively. In these two crops midday C _i decreased with increasing leaf to air water vapor pressure difference. Averaged over all measurement days, the mean C _i across all C₄ species was 198 μmol mol⁻¹, for a C _i/C _a ratio of 0.55. Prior measurements on four herbaceous C₃ species using the same instrument indicated an average C _i/C _a ratio of 0.69. Hence midday C _i values in C ₄ species under field conditions may often be considerably higher and more similar to those of C₃ species than expected from measurements made on plants in controlled environments. Reducing g _s in C₄ crops at low water vapor pressure differences could potentially improve their water use efficiency without decreasing P _N.     

Compensatory effects of elevated CO<Subscript>2</Subscript> concentration on the inhibitory effects of high temperature and irradiance on photosynthetic gas exchange in carrots

We determined the interactive effects of irradiance, elevated CO₂ concentration (EC), and temperature in carrot (Daucus carota var. sativus). Plants of the cv. Red Core Chantenay (RCC) were grown in a controlled environmental plant growth room and exposed to 3 levels of photosynthetically active radiation (PAR) (400, 800, 1 200 μmol m⁻² s⁻¹), 3 leaf chamber temperatures (15, 20, 30 °C), and 2 external CO₂ concentrations (C _a), AC and EC (350 and 750 μmol mol⁻¹, respectively). Rates of net photosynthesis (P _N) and transpiration (E) and stomatal conductance (g _s ) were measured, along with water use efficiency (WUE) and ratio of internal and external CO₂ concentrations (C _i/C _a). P _N revealed an interactive effect between PAR and C _a. As PAR increased so did P _N under both C _a regimes. The g _s showed no interactive effects between the three parameters but had singular effects of temperature and PAR. E was strongly influenced by the combination of PAR and temperature. WUE was interactively affected by all three parameters. Maximum WUE occurred at 15 °C and 1 200 μmol m⁻² s^{− 1} PAR under EC. The C _i /C _a was influenced independently by temperature and C _a. Hence photosynthetic responses are interactively affected by changes in irradiance, external CO₂ concentration, and temperature. EC significantly compensates the inhibitory effects of high temperature and irradiance on P _N and WUE.     

Photosynthetic response of <Emphasis Type="Italic">Quercus ilex</Emphasis> L. plants grown on compost and exposed to increasing photon flux densities and elevated CO<Subscript>2</Subscript>

Quercus ilex plants grown on two different substrates, sand soil (C) and compost (CG), were exposed to photosynthetic photon flux densities (PPFD) at 390 and 800 μmol(CO₂) mol⁻¹ (C₃₉₀ and C₈₀₀). At C₈₀₀ both C and CG plants showed a significant increase of net photosynthetic rate (P _N) and electron transport rate (ETR) in response to PPFD increase as compared to C₃₉₀. In addition, at C₈₀₀ lower non-photochemical quenching (NPQ) values were observed. The differences between C₃₉₀ and C₈₀₀ were related to PPFD. The higher P _N and ETR and the lower dissipative processes found in CG plants at both CO₂ concentrations as compared to C plants suggest that substrate influences significantly photosynthetic response of Q. ilex plants. Moreover, short-term exposures at elevated CO₂ decreased nitrate photo-assimilation in leaves independently from substrate of growth.     

吡啶酮类衍生物对5-脂氧合酶的抑制作用

合成了一系列3-羟基-4(1H)-吡啶酮类衍生物,并研究了它们对5-脂氧合酶的抑制作用. 发现6-取代-3-羟基-4(1H)-吡啶酮化合物(2a～2e)对5-脂氧合酶具有显著抑制作用, 特别是6-苯硫基-1-苯基-2-甲基-3-羟基-4(1H)-吡啶酮(2a)的抑制效果最好(IC₅₀=2.52 μmol/L). 6-位没有取代基的羟基吡啶酮类化合物对5-脂氧合酶却没有抑制作用. 讨论了6-取代-3-羟基-4(1H)-吡啶酮类化合物对5-脂氧合酶的抑制作用机制.     

Differential inhibition of photosynthesis under drought stress in <Emphasis Type="Italic">Flaveria</Emphasis> species with different degrees of development of the C<Subscript>4</Subscript> syndrome

The effect of drought stress (DS) on photosynthesis and photosynthesis-related enzyme activities was investigated in F. pringlei (C₃), F. floridana (C₃–C₄), F. brownii (C₄-like), and F. trinervia (C₄) species. Stomatal closure was observed in all species, probably being the main cause for the decline in photosynthesis in the C₃ species under ambient conditions. In vitro ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBPCO) and stromal fructose 1,6-bisphosphatase (sFBP) activities were sufficient to interpret the net photosynthetic rates (P _N), but, from the decreases in P _N values under high CO₂ (C _a = 700 μmol mol^{− 1}) it is concluded that a decrease in the in vivo rate of the RuBPCO reaction may be an additional limiting factor under DS in the C₃ species. The observed decline in the photosynthesis capacity of the C₃–C₄ species is suggested to be associated both to in vivo decreases of RuBPCO activity and of the RuBP regeneration rate. The decline of the maximum P _N observed in the C₄-like species under DS was probably attributed to a decrease in maximum RuBPCO activity and/or to decrease of enzyme substrate (RuBP or PEP) regeneration rates. In the C₄ species, the decline of both in vivo photosynthesis and photosynthetic capacity could be due to in vivo inhibition of the phosphoenolpyruvate carboxylase (PEPC) by a twofold increase of the malate concentration observed in mesophyll cell extracts from DS plants.     

蝎毒素BmkTXKβ对家兔心房肌细胞瞬间外向钾电流的抑制作用

为研究蝎毒素BmkTXKβ对家兔心房肌细胞瞬间外向钾电流(I_to)的影响,采用全细胞膜片钳技术记录应用BmkTXKβ前后的I_to电流. 结果显示BmkTXKβ（1 μmol/L）使心房肌细胞I_to（刺激电压为+50 mV）从（13.63±0.87）pA/pF减少到（7.98±0.78）pA/pF,抑制率为41.4% (n=16, P＜0.001).冲洗后, I_to部分恢复至(11.18±0.82)pA/pF (n=6, P＜0.01,与给药后比较).在0.01～100 μmol/L范围内BmkTXKβ呈浓度依赖性地抑制I_to,IC₅₀的均值为0.95 μmol/L (n=10, P＜0.01),但无频率依赖性(n=6,P＞0.05). 1 μmol/L的BmkTXKβ可使I_to通道的失活动力学曲线明显左移,V_1/2分别为（－23.6±2.7） mV和（－35.3±3.6） mV（n=8,P＜0.05）,曲线斜率基本不变.同时可使I_to通道的恢复过程明显减慢,恢复曲线右移,τ值从（51.2±8.5） ms延长至（93.5±13.4） ms（n=9,P＜0.01）,但不影响其激活过程.据此推断BmkTXKβ对家兔心房肌细胞I_to具有显著的抑制作用,主要作用于失活过程,延长该通道的恢复时间.     

典型温带雨养泥炭沼泽湿地地下部二氧化碳和甲烷浓度变化规律及其影响因素

为研究北方泥炭沼泽湿地二氧化碳（CO₂）和甲烷（CH₄）浓度随深度的变化规律及其影响因素,选取欧洲北部典型雨养泥炭地贝尔山湿地（BBM）和舒特兹山湿地（SBM）两个采样点,通过原位采集泥炭剖面温室气体、孔隙水以及土壤样品,结合傅里叶变换红外光谱（FTIR）技术、碳氮同位素技术,探讨泥炭土壤的分解程度及温室气体浓度变化的关系。研究结果表明：（1）BBM采样点地下部的CO₂浓度变化规律总体呈现随深度波动减少趋势,值多在3000 μmol/L附近波动,最大值为4210.74 μmol/L（120 cm）,SBM采样点的CO₂浓度随深度先增后减,60 cm以上在1800 μmol/L附近波动,60 cm以下在3000 μmol/L附近波动,最大值为4191.94 μmol/L（90 cm）;BBM和SBM地下部CH₄浓度都随深度增大,并且在60cm以下浓度增加较快,BBM最大值为735.90 μmol/L（260 cm）,SBM最大值为543.51 μmol/L（170 cm）。（2）BBM和SBM的δ¹³C_CH4的值均较小,表明大部分的¹²CH₄仍被储存在泥炭土壤中,而两个采样点的δ¹³C_CO2和分馏系数α_c均随深度增加,表明泥炭土中产甲烷方式为浅层以乙酸产甲烷为主,深层以H₂还原CO₂为主。（3）C/N、碳氮同位素比值、FTIR均显示SBM和BBM的有机质分解程度较低,因为两个采样点的低可溶性有机碳浓度和低pH值不利于分解,表明该地储存着大量有机碳。通过探讨北温带典型泥炭地温室气体的浓度变化规律及其影响因素,结果可为全球泥炭湿地碳排放提供理论支撑。     

Intrinsic changes in photosynthetic parameters of carrot leaves under increasing CO<Subscript>2</Subscript> concentrations and soil moisture regimes

A controlled growth chamber experiment was conducted to investigate the short-term water use and photosynthetic responses of 30-d-old carrot seedlings to the combined effects of CO₂ concentration (50–1 050 μmol mol⁻¹) and moisture deficits (−5, −30, −55, and −70 kPa). The photosynthetic response data was fitted to a non-rectangular hyperbola model. The estimated parameters were compared for effects of moisture deficit and elevated CO₂ concentration (EC). The carboxylation efficiency (α) increased in response to mild moisture stress (−30 kPa) under EC when compared to the unstressed control. However, moderate (−55 kPa) and extreme (−70 kPa) moisture deficits reduced α under EC. Maximum net photosynthetic rate (P _Nmax) did not differ between mild water deficit and unstressed controls under EC. Moderate and extreme moisture deficits reduced P _Nmax by nearly 85 % compared to controls. Dark respiration rate (R _D) showed no consistent response to moisture deficit. The CO₂ compensation concentration (Γ) was 324 μmol mol⁻¹ for −75 kPa and ranged 63–93 μmol mol⁻¹ for other moisture regimes. Interaction between moisture deficit and EC was noticed for P _N, ratio of intercellular and ambient CO₂ concentration (C _i/C _a), stomatal conductance (g _s ), and transpiration rate (E). P _N was maximum and C _i/C _a was minimum at −30 kPa moisture deficit and at C _a of 350 μmol mol⁻¹. The g _s and E showed an inverse relationship at all moisture deficit regimes and EC. Water use efficiency (WUE) increased with moisture deficit up to −55 kPa and declined thereafter. EC showed a positive influence towards sustaining P _N and increasing WUE only under mild moisture stress, and no beneficial effects of EC were noticed at moderate or extreme moisture deficits.     

Entwicklungsgeschichte und Ultrastruktur von Pollenkitt und Exine bei nahe verwandten entomophilen und anemophilen Angiospermensippen derAlismataceae,Liliaceae, Juncaceae,Cyperaceae, Poaceae undAraceae

Some closely related members of the monocotyledonous familiesAlismataceae, Liliaceae, Juncaceae, Cyperaceae, Poaceae andAraceae with variable modes of pollination (insect- and wind-pollination) were studied in relation to the ultrastructure of pollenkitt and exine (amount, consistency and distribution of pollenkitt on the surface of pollen grains). The character syndromes of pollen cementing in entomophilous, anemophilous and intermediate (ambophilous or amphiphilous) monocotyledons are the same in principal as in dicotyledons. Comparing present with former results one can summarize: 1) The pollenkitt is always produced in the same manner by the anther tapetum in all angiosperm sub-classes. 2) The variable stickiness of entomophilous and anemophilous pollen always depends on the particular distribution and consistency of the pollenkitt, but not its amount on the pollen surface. 3) The mostly dry and powdery pollen of anemophilous plants always contains a variable amount of inactive pollenkitt in its exine cavities. 4) A step-by step change of the pollen cementing syndrome can be observed from entomophily towards anemophily. 5) From the omnipresence of pollenkitt in all wind-pollinated angiosperms studied one can conclude that the ancestors of anemophilous angiosperms probably have been zoophilous (i.e. entomophilous) throughout.

     

Identification and Characterization of the First Equine Parainfluenza Virus 5

正Dear Editor,Parainfluenza virus 5 (PIV5), known as canine parainfluenza virus in the veterinary field, is a negative-sense,nonsegmented, single-stranded RNA virus belonging to the Paramyxoviridae family (Chen 2018). The virus was first reported in primary monkey kidney cells in 1954 (Hsiung1972), then it has been frequently discovered in various     

Pathogenic Characterization and Full Length Genome Sequence of a Reassortant Infectious Bursal Disease Virus Newly Isolated in Pakistan

<正>Dear Editor,Infectious bursal disease (IBD) is one of the most important diseases of the poultry. The IBD virus (IBDV), a nonenveloped virus belonging to the Birnaviridae family with a genome consisting of two segments of double-stranded RNA (segments A and B), targets B lymphocytes of bursa of Fabricious leading to immunosuppression. In Pakistan,poultry farming is the second biggest industry and IBD is the second biggest disease threating the poultry sector.However, there is limited genome information of IBDV     

Similar aerosol emission rates and viral loads in upper respiratory tracts for COVID-19 patients with Delta and Omicron variant infection

Highlights
1 Aerosol emission rates of Delta or Omicron patients were similar.
2 Viral loads in upper respiratory tract of Alpha, Delta and Omicron patients were similar.
3 Viral loads in upper respiratory tract of vaccinated or unvaccinated Delta patients had no difference.     

Recombinant human interferon-α1b inhibits SARS-CoV-2 better than interferon-α2b in vitro

Highlights
1) A comprehensive evaluation method for anti-SARS-CoV-2 drugs was established based on RT-qPCR, TCID₅₀ method, and immunofluorescence.
2) A significant antiviral effect of rHuIFN-α1b was shown with EC₅₀=0.12 IU/mL in Vero cells and EC₅₀=0.52 IU/mL in Calu-3 cells, which was better than rHuIFN-α2b (EC₅₀=0.25 IU/mL in Vero cells and EC₅₀=2.48 IU/mL in Calu-3 cells).
3) rHuIFN-α1b has a good potential in the application of anti-COVID-19 therapy.     

Continued antigenic variation of highly pathogenic avian influenza A (H7N9) virus in laying hens in China, 2020–2021

Highlights
1. 13 strains of H7N9 viruses from laying hens in 2020 and 2021 were identified.
2. H7N9 viruses in China comprised at least 11 genotypes.
3. H7N9 viruses are high pathogenic in chickens, not in ducks.
4. The most H7N9 viruses cross-reacted poorly with H7-Re3 antiserum.
5. The H7-Re3 vaccine was unable to prevent H7N9 infection.