光对柑桔组培无性系芽梢的生根效应

 以建水无籽蜜桔(Citrus reticulate)4个幼胚繁殖的芽梢为材料.实验结果表明: (1)芽梢接种后经4天暗培养再置于白光下继续培养的比未经暗处理的能提高生根率3.8%,提高生根势63.9%.若延长培养时间,则有明显的抑制作用. (2)3000Lux的白色光强有益于生根. (3)光谱中650nm的单色红光(光强300～430Lux)比白色光能提高生根率25.3%～39.7%,提高生根势47.3%～51.4%,且能加速生根进程和根系生长.红光主要作用时间在接种后的第4天以后.550 nm的单色黄光(光强443～1800 Lux)与白光相比,效果不太明显.410 nm的单色蓝光在低光强(460 Lux)时具有一定正效应.当光强增至600 Lux时,往往具有负效应.     

不同光照强度对石栎幼苗叶绿素含量及叶绿素荧光参数的影响

以亚热带常绿阔叶林中的常见种石栎(Lithocarpus glaber)为研究材料,测定了不同光强条件(100%、75%和50%自然光强)下幼苗叶绿素荧光参数及叶绿素含量,探讨了石栎生长对光强的适应性。结果表明,随着光照强度的减弱,石栎叶片的叶绿素含量上升,3种光强条件下叶片光系统Ⅱ的实际光化学效率(ΦPSII)、最大光能转化效率(Fv/Fm)和潜在活性(Fv/Fo)的季节变化规律相似,高光强下的ΦPSII、Fv/Fm和Fv/Fo值相对较小,说明石栎幼苗能适应较大的光强幅度,同时对低、弱光强有一定的抗逆性。     

不同光强对结果期草莓光合特性的影响

[目的]探索草莓光合特性的生理机制,为草莓的育苗和露地栽培提供理论指导。[方法]以草莓品种达赛莱克特为材料,在-1.28、-3.58-、5.56 MPa 3个叶片水势下研究不同光照强度对结果期草莓光合作用的影响。[结果]光照强度对结果期草莓的光合速率具有显著影响,光合速率在光照强度1200~1500μmol/(m2.s)之间出现峰值。叶片水势越高,光照强度对光合速率的影响越明显。随着光照强度的增加,叶片气孔导度下降,水势较低的叶片气孔导度下降的趋势更明显。不同水势叶片的胞间二氧化碳浓度和气孔限制值在光照强度增加过程中表现出不同的变化趋势。[结论]叶片水势较高时造成光合速率下降的因素是非气孔因素,叶片水势较低时气孔因素是造成光合速率下降的主要因素。     

Optimal Light Intensity and Nitrogen-to- Phosphorus Ratio for Growth of Nitzschia capitellata Hust,

[目的]为进一步探索小头端菱形藻（Nitzschia capitellata Hust.）作为优质饵料、生物能源的潜能,在室内条件下对小头端菱形藻生长的最适光照强度、氮磷比等培养条件进行研究。[方法]设定不同光照度梯度,在相同营养、温度（25±1）℃以及光周期（12 h/12 d）下进行培养,筛选得出最适光照强度,其次将氮磷比设置为5∶1、6∶1、7∶1和8∶1,置于相同条件进行培养。[结果]在3000 lx的光照度下,小头端菱形藻的藻比增殖率和现存量最高,分别为0.51 d-1和7.97×104 cells/ml。在氮磷比为6∶1条件下,小头端菱形藻生长最佳。[结论]小头端菱形藻的最适光照度为3000 lx,最适氮磷比为6∶1。     

Phytochrome-mediated bioelectric potentials in mung bean seedlings

Excised root tips from dark-grown mung bean seedlings (Phaseolus aureus) that adhere to a negatively charged glass surface when irradiated with red light and release when irradiated by far-red light develop a positive bioelectric potential (about 1.0 millivolt) at the tip in red light and a negative bioelectric potential in far-red light. The sign of the bioelectric potential was repeatedly photo-reversible, and the adhesion and release kinetics were similar to those of the development of the bioelectric potentials. Photoconversion of the phytochrome holochrome perhaps changes permeability characteristics of the cell membrane, resulting in an induced localized electrochemical gradient manifested as a bioelectric potential. This supports the view that phytochrome in situ is membrane bound.     

Light modulates voltage-dependent potassium channels in limulus ventral photoreceptors

Voltage-dependent outward current measured in the dark is reduced after illumination. This reduction can be blocked by tetraethylammonium and is associated with a decrease in total membrane conductance. The voltage dependence of the current reduced by light is the same as that of the delayed rectifier. These results indicate that light modulates the delayed rectifier. This modulation serves to maintain a stable voltage response to constant illumination.     

Reversal response elicited in nonbeating cilia of paramecium by membrane depolarizatin

Ciliary reversal occurs in response to electrical and chemical stimuli in specimens of Paramecium caudatum in which ciliary beat has been completely inhibited by external application of nickel ions. The mechanism underlying ciliary reversal appears, therefore, to differ from that of ciliary beat. The cessation of ciliary beat has no effect on the intracellular potential of Paramecium. However, depolarizing action potentials are associated with ciliary reversals in paramecia, treated with nickel, without ciliary beat. Thus, membrane depolarization in this species seems specifically concerned with the ciliary reversal, and not with ciliary beat.     

Slow synaptic excitation in sympathetic ganglion cells: evidence for synaptic inactivation of potassium conductance

The slow excitatory postsynaptic potential (EPSP) was investigated in frog sympathetic ganglion cells. In contrast to the increased conductance associated with other known EPSP's, during the slow EPSP resting membrane conductance was decreased. Electrical depolarization of the membrane potentiated the slow EPSP, whereas progressive hyperpolarization decreased its size and then reversed it to a hyperpolarizing potential (the opposite of the effect of membrane polarization on other EPSP's). The reversal potential of the slow EPSP was close to the potassium equilibrium potential. We propose that the slow EPSP, in contrast to classical EPSP's, is generated by an inactivation of resting potassium conductance.     

Ammonium and chloride extrusion: hyperpolarizing synaptic inhibition in spinal motoneurons

The reversal potential of postsynaptic inhibition shifts toward resting membrane potentials in cat spinal motoneurons after intravenous infusion of ammonium salts(1 to 3 millimoles per kilogram of body weight). Simultaneously, the depolarizing action of intracellularly injected chloride ions on the inhibitory membrane is enhanced and recovery therefrom is prolonged. Passive membrane properties remain unaltered. The results indicate a blocking of active extrusion of chloride which normally maintains a high ionic gradient for hyperpolarizing inhibition.     

遮光对Pb胁迫下白花泡桐叶片生理响应的影响

[目的]研究光环境变化条件下,白花泡桐叶片对Pb胁迫的生理响应。[方法]在全光照、50％、20％光照条件下,对不同Pb处理下白花泡桐叶片生理特性进行研究。[结果]Pb处理下,SOD、CAT、APX均在20％光照处有最小活性,而POD在该条件下有最大活性。在Pb处理时,白桦泡桐叶片光合色素含量在20％光照条件下达最小值。丙二醛和脯氨酸随光照强度减弱呈现先减后增的趋势,而膜透性在处理组中呈现逐渐下降的趋势。Pb处理下,超氧阴离子自由基和过氧化氢含量随光照强度减弱呈现先减少后增加的趋势。[结论]适当的遮光处理缓解了Ph胁迫对白花泡桐叶片的氧化损害。     

光照强度与GA_3浓度对云烟99种子萌发的影响

为云烟99烤烟新品种的推广应用提供参考,以云烟99种子为试验材料,采用室内培养皿发芽试验研究不同光照强度和GA_3浓度对云烟99种子萌发的影响。结果表明:适宜光照强度和GA_3浓度对云烟99烤烟种子的萌发有促进作用。在相同GA_3浓度下,除GA_3浓度为50mg/L处理的云烟99种子发芽势和发芽率随光照强度增加呈持续升高趋势外,其余GA_3浓度处理均随光照强度增加呈先升高后降低趋势,且在光照强度为3 700lx时达最大;发芽指数、烟苗长度及活力指数随光照强度增加均呈先升高后降低趋势,且多在光照强度为3 700lx时达最大;发芽时间随光照强度增加呈先降低后升高趋势,且在光照强度为3 700lx时最短。在相同光照强度下,云烟99种子的发芽率和发芽势以GA_3浓度为50mg/L和100mg/L处理最高;发芽指数、活力指数和烟苗长度以GA_3浓度为100 mg/L处理最高,发芽时间以GA_3浓度为50mg/L处理最短。不同光照强度对云烟99种子的发芽指数、发芽时间、苗长和活力指数的影响达极显著水平(P0.01),对发芽势的影响达显著水平(P0.05);不同GA_3浓度对云烟99种子发芽时间的影响达显著水平(P0.05),对发芽势、发芽率、发芽指数、苗长和活力指数的影响达极显著水平(P0.01);光照强度和GA_3浓度互作对云烟99苗长和活力指数的影响达极显著水平(P0.01)。3 700lx光照强度和100mg/L GA_3浓度组合有利于云烟99烤烟种子萌发。     

Paleomagnetic Study of a Reversal of the Earth's Magnetic Field

A detailed record of a field reversal has been obtained from the natural remanent magnetization of the Tatoosh intrusion in Mount Rainier National Park, Washington. The reversal took place at 14.7 +/- 1 million years and is interpreted to be from reverse to normal. A decrease in the intensity of the field of about an order of magnitude occurs immediately before the reversal, while its orientation remains substantially unchanged. The onset of the reversal is marked by abrupt swinging of the virtual geomagnetic pole along an arc of a great circle. During the reversal the pole traces a path across the Pacific. In the last stage of the process recorded in the sections, the succession of virtual geomagnetic poles is very similar to those generated by secular variation in the recent past. Although the cooling rate of the intrusion is not sufficiently well known to permit a useful calculation of the duration of the reversal process, an estimate based on the length of the supposed secular variation cycles gives 1 to 4 x 103 years for the reversal of field direction and approximately 1 x 104 years for the time scale of the intensity changes.     

营养液膜水培樱桃番茄对弱光的逆境适应性

在华东型连栋塑料大棚内对一部分水培番茄和土培番茄设置遮阳网进行遮阳处理,观察结果期在弱光条件下某些生理指标的变化,结果表明,弱光大幅度降低了土培番茄的根系活力、清晨叶水势和光合速率,水培番茄在遮阳条件下这些生理指标虽有降低,但程度较土培番茄为低。因此,水培樱桃番茄在保护地栽培中对弱光环境的适应性要优于土培番茄。     

光照强度对工厂化棉苗形态和生理特性的影响

为了探索光照强度对工厂化棉苗形态和生理特性的影响,采用不同的光照强度,测定不同出苗天数工厂化棉苗的单株鲜重、根鲜重、有效根数、根叶比、叶片数、叶片厚度、叶重、叶片水势、叶绿素含量等指标。结果表明:随着光照强度的增加,不同出苗天数棉苗各项指标都增加,可见,高光照对工厂化棉苗的生长发育有一定的促进作用。同时,随着光照强度的增加,棉花返苗期缩短。综合来看,出苗20d的棉苗最适合移栽。     

Electrically controlled nonlinear generation of light with plasmonics

Plasmonics provides a route to develop ultracompact optical devices on a chip by using extreme light concentration and the ability to perform simultaneous electrical and optical functions. These properties also make plasmonics an ideal candidate for dynamically controlling nonlinear optical interactions at the nanoscale. We demonstrate electrically tunable harmonic generation of light from a plasmonic nanocavity filled with a nonlinear medium. The metals that define the cavity also serve as electrodes that can generate high direct current electric fields across the nonlinear material. A fundamental wave at 1.56 micrometers was frequency doubled and modulated in intensity by applying a moderate external voltage to the electrodes, yielding a voltage-dependent nonlinear generation with a normalized magnitude of ~7% per volt.     

Synaptic current at the squid giant synapse

Transmission in the giant synapse of squid was studied by measuring synaptic currents in the voltage-clamped postsynaptic giant axon. These currents varied linearly with the axon's membrane potential, and showed an intercept on the voltage axis at, or near, the sodium equilibrium potential. The intercept shifted in seawater containing less sodium by even more than the shift in the sodium equilibrium potential. It is concluded that the transmitter at this synapse causes a significant change in the sodium conductance only.     

光强对黄檗幼苗生长及抗氧化酶活性的影响

通过遮阴,使黄檗(Phellodendron amurense)幼苗生长在相对光强分别为100％、75％、50％和25％的环境下处理100 d,探讨光照强度对黄檗幼苗生长和抗氧化能力的影响。结果表明,黄檗幼苗在75％的光强下生长最好。随着光强进一步减弱,幼苗的鲜质量减少、根冠比增大、叶绿素含量增加而叶绿素a/b减小。随着环境光强的增加,黄檗幼苗的丙二醛(MDA)含量增加,超氧化物歧化酶(SOD)、过氧化物酶(POD)和过氧化氢酶(CAT)的活性增强(相对光强75％的幼苗偶有例外)。强光虽然加剧了膜脂过氧化作用,但幼苗的抗氧化能力也有一定程度的提高。强光不利于黄檗幼苗期的生长发育。对于人工栽培的黄檗,在幼苗期应适当遮阴(试验的相对光强为75％),则更有利于其生长。     

Visible Light from Semiconductors: Luminescence from p-n junctions and potential uses of solid state light sources are discussed

Electroluminescence from semiconductor diode light sources can occur as a result of the application of a direct current at a low voltage to a suitably doped crystal containing a p-n junction. In recent years, it has become apparent that in some materials the efficiency of conversion of electric energy to visible light can be appreciably high. Since light-emitting diodes are compatible with the present electronic circuitry, they have many potential applications.     

Autonomic regulation of a chloride current in heart

In isolated heart cells, beta-adrenergic receptor stimulation induced a background current that was suppressed by simultaneous muscarinic receptor stimulation. Direct activation of adenylate cyclase with forskolin also elicited this current, suggesting regulation by adenosine 3',5'-monophosphate (cAMP). This current could be recorded when sodium, calcium, and potassium currents were eliminated by channel antagonists or by ion substitution. Alteration of the chloride equilibrium potential produced changes in the reversal potential expected for a chloride current. Activation of this chloride current modulated action potential duration and altered the resting membrane potential in a chloride gradient-dependent manner.     

一种光伏发电DC-DC变换器

在光伏发电系统中为了控制蓄电池的充放电的稳定性,保护系统的安全性,设计了一种以非隔离型的Buck/Boost拓扑结构为主电路的DC-DC变换器、设计了电路的参数,提出了基于电压、电流双闭环的控制算法,采用微处理器TMS320F28335为控制核心,开发了控制系统.实验结果表明：该DC-DC变换器具有输入电压范围广、输出电压精度高以及良好的动态、稳态特性.