松嫩平原碱化草甸星星草种群分蘖株延长生殖生长的表型可塑性调节

在松嫩平原碱化草甸,采用大样本随机取样的方法,研究了不同时间到达抽穗初期、抽穗期、开花期和乳熟期的星星草种群生殖分蘖株数量性状的可塑性及其调节规律.结果表明：除在开花期存在一定的波动外,在每5 d的时间里,随着生殖生长时间的延长, 星星草种群在抽穗初期、抽穗期和乳熟期的生殖分蘖株高、分蘖株生物量、花序长和花序生物量均依次显著增加.各生育期的星星草种群生殖分蘖株高与花序生物量呈显著正相关,而与生殖分配呈显著负相关.随着生殖生长时间的延长,抽穗初期、开花期和乳熟期的星星草花序生物量随着分蘖株高增加,其幂函数的增长速率均呈增大趋势.生殖生长时间延长10 d,其抽穗初期和抽穗期的生殖分配直线下降速率分别降低了43.2%和44.31%;延长5 d,乳熟期的下降速率降低了130%.表明星星草种群分蘖株生殖生长的表型可塑性调节遵循着一定的规律.     

Floret Initiation and Development in Spring Wheat (Triticum aestivum L.)

The number and developmental stages of florets were determinedin each spikelet of the spike in the main shoots of spring wheat.Samples were taken frequently from plants grown in a phytotronand in a nitrogen application field-test. Ten stages of development,from floret initiation until anthesis, were recognized and described. Inter-spikelet variation in the total number of initiated floretswas rather small. However, the number of florets at advancedstages of development, as well as the number of grains, washighest in the central spikelets in which florets initiatedfirst. Floret initiation did not proceed beyond spike emergence,whereafter the distal florets and the spikelet apex degenerated.Grain-set was restricted to florets which had developed at leastto the stage of visible anther lobes at spike emergence. Thenumber of these florets was increased significantly by nitrogenapplication. Wheat, Triticum aestivum L., spikelet, floret, grain set, nitrogen     

Ca-activated potassium conductance in metabolically exhausted skeletal muscle fibres

Frog skeletal muscle fibres, when stimulated at low frequencies (1–5 Hz) until contractile activity ceases, show a drastic increase in potassium conductance. This results in an increased resting potential and a nearly complete disappearance of the afterpotential which follows a spike [1,2]. The origin of this phenomenon and some implications have been investigated and discussed in several publications from our laboratory. We summarize the main results in this review.     

Up-regulation of the Kv3.4 potassium channel subunit in early stages of Alzheimer's disease

Gene expression throughout the different stages of Alzheimer's disease was analysed in samples from cerebral cortex. The gene encoding the voltage-gated potassium channel Kv3.4 was already overexpressed in early stages of the disease, and in advanced stages Kv3.4 was present at high levels in neurodegenerative structures. This subunit regulates delayed-rectifier currents, which are primary determinants of spike repolarization in neurones. In unique samples from a patient with Alzheimer's disease whose amount of amyloid plaques was decreased by beta amyloid immunization, Kv3.4 was overexpressed. The channel subunit was expressed in the neuropil, in the remaining conventional plaques in the frontal cortex and in collapsed plaques in the orbitary cortex. Therefore, amyloid deposition in plaques does not seem to be responsible for the increase in Kv3.4 levels. Nevertheless, Kv3.4 up-regulation is related to amyloid pathology, given that transgenic mice with the Swedish mutation of amyloid precursor protein showed increased expression of Kv3.4. Up-regulation of voltage-gated potassium channel subunits alters potassium currents in neurones and leads to altered synaptic activity that may underlie the neurodegeneration observed in Alzheimer's disease. Thus, Kv3.4 likely represents a novel therapeutic target for the disease.     

Categories of resistance at four growth stages in three wheats resistant to the Russian wheat aphid (Homoptera: Aphididae)

Laboratory experiments were conducted to determine categories of resistance to Russian wheat aphid, Diuraphis noxia (Mordvilko), in three wheats, Triticum aestivum L, (PI 372129, PI 243781, and PI 222668) at Zadoks growth stages 10, 20, 30, and 40. 'TAM 107' was used as the susceptible standard. Antixenosis was observed in PI 222668 and PI 372129. Antibiosis was expressed as reduced nymphipositional period, daily nymph production, and fecundity at the jointing (Zadoks 30) and boot (Zadoks 40) stages in PI 243781 and at tillering (Zadoks 20) in TAM 107. Antibiosis, expressed as reduced intrinsic rate of increase, was observed in PI 222668 at tillering (Zadoks 20). Tolerance to chlorosis and leaf rolling was expressed in the three resistant wheats at all growth stages tested. Tiller production, floret formation, spike length and wet weight were affected by Russian wheat aphid feeding after Zadoks 10. Reduction in spike length did not occur in PI 372129 and PI 243781.     

表油菜素内酯喷施时期对宽幅播种小麦产量和氮素利用率的影响

为明确协同提高宽幅播种小麦产量和氮素利用率的表油菜素内酯喷施时期,研究了不同生育时期喷施表油菜素内酯对小麦产量和氮素吸收利用的影响。结果表明: 与喷施清水对照相比,喷施表油菜素内酯可通过提高小麦穗粒数或(和)千粒重提高产量,通过促进地上部氮素积累提高氮素吸收效率,进而提高氮素利用率,但不同时期喷施效果存在差异。起身期+灌浆期、拔节期+灌浆期、起身期+拔节期+灌浆期、起身期+开花期+灌浆期喷施处理在所有处理中穗粒数和千粒重增幅最大,产量增幅最高(12.8%～14.0%);同时地上部氮素积累量增幅最大,氮素吸收效率增幅最高(16.4%～18.8%),从而氮素利用率增幅最高。综合施用成本等因素,生产上可采用起身期+灌浆期或拔节期+灌浆期2次间隔喷施模式,实现宽幅播种小麦高产高效栽培。     

不同穗型冬小麦品种根系时空分布特征及其碳氮代谢的研究

在大田柱栽试验条件下,对2种穗型冬小麦品种根系的时空变化及其碳氮代谢进行了研究。结果表明,2种穗型冬小麦品种的单株根系干重、根重密度随生育时期逐渐增加,均在抽穗期达到最大值;不同土壤深度的根系活力随生育时期的变化不一致,2品种0～20 cm根系活力的变化趋势从越冬期逐渐下降,在抽穗期达到较低值后缓慢上升,并于灌浆期出现一个小的峰值;根系中可溶性糖含量、含氮量均从越冬期开始下降,在抽穗期达到最低值, 随后在开花期又出现一个峰值后缓慢下降。2种穗型冬小麦品种相比,重穗型小麦品种的根系各项指标略高于多穗型品种;在不同土层深度之间,各项指标总体趋势为随着土层深度加深逐渐下降,但是在不同生育时期,各土层之间出现有个别波动现象。     

开放式空气二氧化碳浓度增高对小麦氮素吸收利用的影响

2001—2003年,利用我国唯一的农田开放式空气CO₂浓度增高 (free-air carbon dioxide enrichment,FACE) 技术平台,研究了FACE条件下冬小麦宁麦9号不同生育期N含量、吸收、分配和N效率的响应.结果表明：与对照相比,FACE处理使不同生育时期植株含N率显著降低,降幅达4.4%～13.4%;不同生育时期吸N量显著增加(7.4%～25.4%),生育中期的增幅明显大于生育前、后期;不同生育时期茎鞘的N积累能力相对增强,叶片N积累能力相对减弱,而对麦穗N积累能力的影响因生育进程而异;FACE处理使小麦不同生育时期N物质生产效率(5.5%～10.3%)、成熟期N收获指数(16.3%)和N籽粒生产效率(9.3%)均显著或极显著增加;增施N肥,使小麦不同生育时期N含量和吸收量呈增加趋势,使N效率呈下降趋势,而对N在各器官中分配的影响较小.     

DEVELOPMENT OF THE YOUNG WHEAT SPIKE: A SEM STUDY OF CHINESE SPRING WHEAT

The number of leaves on the main culm was correlated with morphological changes in the wheat spike during development, up to the terminal spikelet stage. The developmental changes were divided into nine stages, which were compared with stages described by other investigators. Several environmental conditions were utilized to determine the consistency of morphological correlations. Although the different environments did influence the length of time required to reach the various stages, the relationship between leaf number and stage of spike development was consistent. Regardless of environmental conditions, all stages were evident. Vernalization period affected the number of spikelets. Plants vernalized 6 wk produced 17–19 spikelets, compared to 21–24 spikelets on plants vernalized 3 wk. There were three major morphological events during spike development: 1) the change from vegetative to reproductive growth, 2) lateral spikelet development, and 3) the initiation and development of the terminal spikelet.     

Thermal dependence of neural activity in the hamster hippocampal slice preparation

1. Neural activity was recorded in an in vitro hamster hippocampal slice preparation while the temperature of the Ringer's solution bathing in the slice was controlled at selected levels. 2. The amplitude of the population spike (action potentials from a group of pyramidal cells) was measured as bath temperature was lowered from 35 degrees C to temperatures where a response could not be evoked. 3. Plots of population spike amplitude versus temperature have bell-shaped curves. The population spikes increased in amplitude as temperature was lowered from 35 degrees C, reached a peak amplitude between 25 and 20 degrees C, and then decreased until a response could not be evoked when temperature was further lowered. 4. These in vitro results obtained in the slice preparation are related to in vivo hippocampal studies. Results are interpreted as consistent with the proposal reviewed here that neural activity in the hippocampus plays a role at specific stages of entrance into and arousal from hibernation.     

Interactions of Calcium with Sodium and Potassium in Membrane Potentials of the Lobster Giant Axon

Experiments were performed on the lobster giant axon to determine the relation between intracellular spike amplitude and external calcium ion concentration. Action potential decline in low external calcium is greatly accelerated by simultaneous removal of external sodium ion. Correlation of the time course of spike decline in low calcium-low sodium solution with the time courses of spike decline in low calcium alone and in low sodium alone indicates that the effect of simultaneous removal of both ions is significantly greater than the sum of the individual effects. For a given time of treatment, spike amplitude was a function of external calcium concentration. While spike height is proportional to the log of the external calcium concentration over the range 2.5 to 50 millimolar, the proportionality constant is dependent upon the sodium concentration. Under the conditions of low external sodium (50 per cent reduction) the slope of the linear relationship between the spike height and the log of the external calcium concentration is about 5 times greater than in normal external sodium. Decreasing external calcium concentration and simultaneously increasing external potassium concentration produce a greater spike reduction than the arithmetic sum of spike reductions in low calcium alone and in high potassium alone. It is suggested that calcium interacts strongly with sodium and potassium in the spike-generating mechanism. A theoretical basis for these results is discussed.     

Dehydrogenase and electrochemical activity of <Emphasis Type="Italic">Escherichia coli</Emphasis> extracts

The dehydrogenase activity of Escherichia coli BB cell extracts was studied at different growth stages in the presence of different substrates and triphenyl tetrazolium chloride as an electron acceptor. It was shown that the highest degree of reduction of triphenyl tetrazolium chloride was observed during exponential growth of the bacteria when potassium isocitrate was used as a substrate. It was found that extracts of the bacteria during the exponential phase of growth on an inert glassy carbon electrode in a three-electrode liquid electrochemical cell manifested electrochemical activity in the presence of potassium citrate and methylene blue or potassium hexacyanoferrate(III) as redox mediators.     

Non-destructive staging of barley reproductive development for molecular analysis based upon external morphology

A prerequisite to study the molecular genetic pathways of pollen and anther development is an accurate staging system for reproductive development. However in barley, floret formation occurs mainly within the pseudostem, which makes the observation of floret development and access to the floret particularly difficult without dissecting the plant. Thus selecting stages for molecular analysis cannot be done non-destructively. A staging method has therefore been developed for barley in order to define the relationship between readily detectable growth points and reproductive development, to provide a clear key to enable accurate selection of reproductive material. Initial staging followed the traditional Zadoks decimal system, with minor adaptations to stages 31-34 and stage 37. The later stages, from 37 onward, were replaced by growth staging based upon the last flag elongation (LFE) and the position occupied by the spike within the pseudostem. Spike size could be readily predicted by using the staging system incorporating Zadoks stages 31-37, supplemented with substages and by LFE staging to improve accuracy. The different spike sizes, as well as the LFE stages, showed a clear relationship to events occurring within the anther, as confirmed by light microscopy of the anthers. The defined relationship between spike size and development to anther development now makes possible the accurate prediction of anther and pollen progression by external staging. This, therefore, provides a mechanism for non-destructive selection of material for analysis that is critical for the molecular characterization of genes in anther and pollen development.     

Phenobarbital: a locus of action on spike broadening and potassium inactivation

1. The effect of phenobarbital on frequency-dependent spike broadening and potassium inactivation was studied in snail neurons. 2. The amount of spike broadening was significantly depressed by the application of 10(-3) M phenobarbital but the time course of broadening was unaffected. 3. In voltage clamped neurons, this concentration of phenobarbital significantly depressed the amount of potassium current inactivation without altering its time constant. 4. A possible locus of phenobarbital's anticonvulsant action is through a decrease in synaptic efficacy resulting from a depression of presynaptic spike broadening.     

Barium, glibenclamide and CGS21680 prevent adenosine A1 receptor changes of ES coupling and spike threshold

Activation of adenosine A1 receptors raised spike thresholds and induced a dissociation of excitatory postsynaptic potential (EPSP) spike coupling in hippocampal pyramidal neurones. This effect could be prevented by activation of A2A adenosine receptors. The A1 receptor agonist N6-cyclopentyladenosine caused a dissociation of the EPSP spike coupling recorded extracellularly and increased the threshold for spike generation measured intracellularly. These effects were prevented by the A2A receptor agonist CGS21680. A series of agents interfering with adenylate cyclase activity, protein kinase A or C, or nitric oxide synthase had no effect on these responses to N6-cyclopentyladenosine. Superfusion with barium or glibenclamide prevented both the dissociation of EPSP spike coupling and the increase of spike threshold. It is concluded that a barium- and glibenclamide-sensitive potassium current may be involved in the postsynaptic effects of A1 receptors on spike threshold, and it is suggested that a similar suppression of a potassium current by A2A receptors could underlie the inhibition of A1 receptor responses.     

Neurotoxic action of some antiarrhythmic agents: comparative effects of propafenone,lidocaine and amiodarone on leech Retzius nerve cell

A series of antiarrhythmic drugs was studied on spontaneous spike activity and depolarizing outward potassium current in leech Retzius nerve cells. Propafenone (0.7 μM/ml) produced a cardiac-like action potential with a rapid depolarization followed by a sustained depolarization or plateau, which is terminated after 250 msec by a rapid repolarization. The effect of lidocaine (0.7 μM/ml) on spontaneous spike activity was less pronounced, and early afterdepolarization has been recorded. Amiodarone at the same and much higher concentrations (3 μM/ml) did not generate either a cardiac-like action potential or an early afterdepolarization. In the voltage clamp experiments, fast and slow calcium-activated outward potassium currents were suppressed with propafenone and lidocaine but not with amiodarone. These results suggest that the antiarrhythmic drugs, propafenone and lidocaine modulate calcium-activated potassium channels in leech Retzius nerve cells.     

河西干旱区白芍养分吸收规律与药效成分积累的关系研究

为揭示河西干旱区白芍干物质积累及营养元素吸收特征和药效成分累积规律,明确影响药效成分积累的营养元素种类,科学制定白芍施肥方案和规范化种植。以甘肃省古浪县古丰镇芍药产业基地4年生白芍为研究对象,通过田间试验测定白芍不同生长期干物质积累特征以及根中9个营养元素含量和3类药效成分含量,并分析白芍根中有效成分含量与营养元素的相关关性。结果表明：（1）随着生育期延续,白芍根部干物质积累先下降后上升,全株干物质积累量逐渐增加,出苗后90-130 d是白芍干物质积累最快的时期,占总积累量的79.29 %,是白芍生长的关键时期。（2）白芍地上部氮、钾含量总体呈下降趋势,而磷素含量总体呈明显增加趋势,而根部氮、磷含量总体呈减少趋势,钾含量变化不明显;地上部和根氮累积总量分别在出苗后130 d和150d达到最高。地上部磷积累量在出苗后150 d达到最大,根部磷积累量分别在出苗后30 d、150 d达到高峰,地上部和根部钾积累量分别在出苗后70 d和150 d达到高峰。地上部氮、钾含量在不同生长时期均高于根部,其磷含量则在出苗后90 d前低于根部,在出苗后110 d后高于根部。（3）根中芍药苷、芍药内酯苷积累量均先升高后降低,最后趋于稳定,多糖积累量表现为高-低-高的变化趋势。（4）芍药苷含量与氮、钙、铜含量呈极显著正相关,与钾含量呈显著正相关,芍药内脂苷含量与氮、钾、钙、铜含量呈极显著正相关,而芍药多糖与各营养元素含量之间没有相关性。可见,白芍氮、磷、钾营养最大效率期在出苗后110～150 d,适时追加氮、钾肥有利于根部生物量的积累,施肥中添加Ca、Cu元素能有效促进白芍药效成分的积累;河西冷凉山区白芍宜在9月中下旬（9月16日以后）采挖。     

Activation-inactivation of potassium channels and development of the potassium-channel spike in internally perfused squid giant axons

A spike that is the result of calcium permeability through potassium channels was separated from the action potential is squid giant axons internally perfused with a 30 mM NaF solution and bathed in a 100 mM CaCl2 solution by blocking sodium channels with tetrodotoxin. Currents through potassium channels were studied under voltage clamp. The records showed a clear voltage-dependent inactivation of the currents. The inactivation was composed of at least two components; one relatively fast, having a time constant of 20--30 ms, and the other very slow, having a time constant of 5--10 s. Voltage clamp was carried out with a variety of salt compositions in both the internal and external solutions. A similar voltage-dependent inactivation, also composed of the two components, was recognized in all the current through potassium channels. Although the direction and intensity of current strongly depended on the salt composition of the solutions, the time-courses of these currents at corresponding voltages were very similar. These results strongly suggest that the inactivation of the currents in attributable to an essential, dynamic property of potassium channels themselves. Thus, the generation of a potassium-channel spike can be understood as an event that occurs when the equilibrium potential across the potassium channel becomes positive.     

Nutrient deficiencies do not contribute to yield loss after waterlogging events in winter wheat (Triticum aestivum)

Frequent waterlogging increases the risk of possible harvest losses in winter wheat. The aim of this study was to analyse which developmental stage of wheat was impaired by waterlogging and whether yield losses can be explained by nutrient deficiences. A large‐scale container experiment was designed to evaluate growth, yield and nutrient status of two wheat cultivars after 14 days of waterlogging at two different developmental stages: DC 31 (first node visible) and DC 51 (beginning of ear emergence). Early waterlogging treatment impaired vegetative growth stages of winter wheat and nutrient uptake, leading to transient nutrient deficiencies, but yield was not significantly reduced. Late waterlogging at the beginning of ear emergence mainly affected generative growth stages and caused yield reductions ranging up to 61%. The main reason for yield loss was the significantly decreased thousand kernel weight in combination with a decreased number of grains per spike. Yield depressions in winter wheat depend on the timing of waterlogging. Early waterlogging transiently reduces vegetative growth through nutrient deficiencies, whereas late waterlogging results in an impaired grain development and associated therewith, yield losses.     

Analysis of the spaceflight effects on growth and development of Super Dwarf wheat grown on the Space Station Mir.

The hypothesis being tested is that Super Dwarf wheat, Triticum aestivum L., plants in the Svet Greenhouse onboard the Russian Space Station Mir will complete a life cycle in spaceflight, providing that the environmental conditions necessary for adequate growth on Earth are supplied. Twenty six seeds of wheat were planted in each of 2 rows of 2 root compartments for a total of 104 seeds in Svet. Germination rate at 7 d was 56 and 73% on Mir and 75 and 90% in ground-based controls. Plants were grown throughout the whole cycle of ontogenesis (123 d) with samples gathered at different times to validate the morphological and reproductive stages of the plants. Young plants showed vigorous early seedling growth, with large biomass production, including the formation of 280 floral spikes. Upon return to Earth, comparative analyses showed that the number of tillers and flowers per spikelet were 63.2% and 40% greater, respectively, in Mir-grown plants than in the controls. By contrast, the stem length (52.4%), spike mass (49.2%) and length (23.1%), awn length (75.7%), number of spikelets per spike (42.8%) and number of seeds per spike (100% sterile) from Mir-grown plants were substantially less than the controls. Distribution of moisture and roots throughout the substrate was very good. All florets on Mir-grown spikes ceased development at the same stage of ontogeny. Lack of caryopses formation was attributed to male sterility occurring at different stages of staminal development. Anthers failed to dehisce and pollen grains were smaller and shriveled compared to the controls, suggesting a chronic stress had occurred in the Svet growth chamber. Recent ground-based studies indicated that ethylene, which was measured at 0.3 to 1.8 mg kg-1 in the Mir, almost certainly could have induced male sterility in the wheat plants grown on the Mir.