脉冲电场作用对植物释放负离子与气孔特征的关系

植物在自然状态下释放负离子的能力很弱,施加脉冲电场可激发其释放能力。在密闭的玻璃箱中,研究紫背竹芋(Stromanthe sanguinea)、绒叶肖竹芋(Calathea zebrina)和朱顶红(Hippeastrum rutilum)在常态、脉冲电场和光照刺激下释放负离子的浓度,并观察叶片气孔特征,结果表明:(1)不同参数脉冲电场对植物释放负离子的能力影响不同,每种植物均具有高效释放负离子的最佳脉冲电场,紫背竹芋为A3B3C3(A3,U=1.5×104 V;B3,T=1.5 s;C3,?=65 ms);绒叶肖竹芋为A3B4C1(A3,U=1.5×104 V;B4,T=2.0 s;C1,?=5 ms);朱顶红为A4B4C1(A4,U=2.0×104 V;B4,T=2.0 s;C1,?=5 ms)。(2)植物体上所储存的电压越大,其释放负离子的能力越强。(3)脉冲电场作用时,植物释放负离子的能力与光照度呈正相关;无电场刺激时两者差异不显著(P0.05)。(4)植物释放负离子的能力与叶片气孔特征关系密切,脉冲电场作用下叶片气孔的开合度和气孔密度越大,其释放能力越强。     

松嫩平原农业区土壤理化性质与真菌代谢产物——球囊霉素相关土壤蛋白的关系

对不同土壤深度的真菌特征代谢产物球囊霉素相关土壤蛋白(glomalin-related soil protein,GRSP)与土壤理化性质相关关系的研究,有助于揭示土壤真菌在不同土壤深度对养分的调节作用。本研究在松嫩平原农田5个土层(0~100 cm)采集360个土样,分析了易提取球囊霉素相关土壤蛋白(EE-GRSP)、总提取球囊霉素相关土壤蛋白(T-GRSP)含量和11个土壤理化性质指标及其相关关系。结果表明:表层EE-GRSP和T-GRSP平均含量为0.74和6.0 mg·g-1,随土层加深均呈显著下降趋势;深层土壤养分储量较大,有机碳、全氮、全磷、全钾、碱解氮、速效磷和速效钾储量在深层(40~100 cm)占总储量的41.2%~62.8%;土壤p H、容重、含水量和电导率也表现了明显的垂直变化规律;各理化性质在不同土层与GRSP的相关关系不同,有机碳在全部深度与GRSP均有显著的相关关系,而p H与GRSP均在20~100 cm深度有极显著的相关性(P0.01),且与EE-GRSP、T-GRSP显著相关的理化性质指标分别在60~80、20~60 cm最多,在表层最少;GRSP在深层土壤与各指标的相关性与表层不同,可能会影响GRSP对不同土壤深度养分的调节功能;鉴于深层土壤中GRSP与养分显著相关,本研究提出,种植与土壤真菌具有共生关系的深根性植物是对富集养分的深层土壤进行生物修复的有效方法。     

Changes in photosynthetic electron transfer and state transitions in an herbicide-resistant D1 mutant from soybean cell cultures

Anomalies in photosynthetic activity of the soybean cell line STR7, carrying a single mutation (S268P) in the chloroplastic gene psbA that codes for the D1 protein of the photosystem II, have been examined using different spectroscopic techniques. Thermoluminescence emission experiments have shown important differences between STR7 mutant and wild type cells. The afterglow band induced by both white light flashes and far-red continuous illumination was downshifted by about 4 °C and the Q band was upshifted by 5 °C. High temperature thermoluminescence measurements suggested a higher level of lipid peroxidation in mutant thylakoid membranes. In addition, the reduction rate of P700⁺ was significantly accelerated in STR7 suggesting that the mutation led to an activation of the photosystem I cyclic electron flow. Modulated fluorescence measurements performed at room temperature as well as fluorescence emission spectra at 77 K revealed that the STR7 mutant is defective in state transitions. Here, we discuss the hypothesis that activation of the cyclic electron flow in STR7 cells may be a mechanism to compensate the reduced activity of photosystem II caused by the mutation. We also propose that the impaired state transitions in the STR7 cells may be due to alterations in thylakoid membrane properties induced by a low content of unsaturated lipids.     

Effects of temperature, photoperiod, and light intensity on the calling rhythm in Arctiid moths

Mean times of onset for calling in Haploa clymene (Brown), Spilosoma virginica (Fabricius), Pareuchaetes insulata (Walker), Cycnia tenera (Hübner), and Euchaetes egle (Drury) advance to earlier times in the photoperiod at lower temperatures. Temperature has no apparent effect on the calling period in Pyrrharctia isabella (J. E. Smith), Spilosoma congrua Walker, and Apantesis nais (Drury). The relationship between the temperatures experienced by each of these species as adults and the response of their calling rhythms to temperature is discussed. Lights-on can elicit calling behaviour in C. tenera, although it is not an absolute requirement because calling eventually begins when lights-on is delayed 4 h and calling also begins prior to lights-on at lower temperatures. Calling periods lengthen in C. tenera and S. congrua when the scotophase is prolonged and in S. congrua after the onset of a lower photophase light intensity (40 lux), suggesting that a higher photophase light intensity (450 lux) inhibits calling and thus causes its termination.

---

Résumé Aux faibles températures le moment moyen de déclenchement de l'appel apparaît plus tôt au cours de la photopériode chez Haploa clymene Brown, Spilosoma virginica Fab., Pareuchaetes insulata Walk., Cycnia tenera Hübn. et Euchaetes egle Drury. La température n'a apparemment pas d'effet sur le moment où l'appel débute chez Pyrrharctica isabella J.E. Smith, S. congrua Walk. et Apantesis nais Drury.L'analyse porte sur les relations entre les températures subies par les adultes de ces espèces et leurs réactions d'appel aux différentes températures. L'apparition de la lumière peut induire le comportement d'appel chez C. tenera, bien que ce ne soit pas indispensable puisqu'il peut éventuellement commencer à des températures plus basses avant l'illumination quand celle-ci est retardée de 4 heures. Les périodes d'appel sont prolongées avec la scotophase chez C. tenera et S. congrua, et même après l'apparition d'une photophase à faible intensité lumineuse (40 lux), l'appel de S. congrua se poursuit, ce qui suggère que les photophases à intensité lumineuse plus élevée (450 lux) inhibent l'appel et ainsi en provoquent la fin.

     

FACTORS LIMITING EDAPHIC ALGAL BIOMASS AND PRODUCTIVITY IN A GEORGIA SALT MARSH1,2

A “planted core” system was developed to test the effect of short term (1–2 weeks) experimental manipulation of environmental parameters on edaphic microalgae under field conditions. A large number of small cores (surface area = 7 cm²) were collected, randomized and replanted in the marsh in fiddler crab exclosures with appropriate experimental treatments. Daily enrichment of the cores with NH₄⁺ resulted in significant increases in edaphic primary productivity and levels of chlorophyll a in both summer and winter seasons in the short-Spartina marsh. Enrichment with a complete nutrient solution caused no further increases. Nutrient enrichment of creekbank sediments was much less stimulatory to the resident algal assemblage. In both sites, but especially in the creekbank, the removal of fiddler crab grazers resulted in significant increases in chlorophyll a and productivity. Experimental manipulation of light intensity showed that the average light intensity reaching the sediment surface was saturating for chlorophyll production in the short-Spartina marsh. A reciprocal transplant experiment involving unfertilized cores from the short-Spartina marsh and creekbank marsh demonstrated that NH₄⁺ inputs occurring in the creekbank site rapidly alleviated nitrogen limitation of edaphic algae from short-Spartina marsh. Algae in creekbank cores incubated in the short-Spartina marsh were unable to sustain high productivity once the original standing stock of NH₄⁺ declined.     

火烧强度对中亚热带人工造林初期土壤呼吸的影响

在热带和亚热带森林中,火烧是一种清理采伐迹地的有效管理措施。尽管许多研究表明,火烧刺激了土壤的碳排放,但对亚热带火强度对土壤呼吸的影响还缺乏了解。在中亚热带米槠常绿阔叶次生林采伐迹地上,设置高火烧强度（HF）、低火烧强度（LF）炼山造林处理,利用LI-8100对造林初期（2012年3月-2012年12月）土壤呼吸进行测定,同时监测观测期土壤温度、含水量以及降雨量等气象因子,分析不同火烧强度对中亚热带造林初期土壤呼吸及排放量的影响,同时探讨影响土壤呼吸变化的主要因素。结果表明：（1）观测期间不同火烧强度对土壤呼吸的影响呈现出明显的时间变化特征：与对照（CT）相比,土壤呼吸在火烧后2个月以内显著增加（P<0.05）,HF和LF分别增加76.3%和55.3%;在火烧后2-5个月内三种处理间没有显著差异（P>0.05）;但之后,火烧处理土壤呼吸显著低于CT （P<0.05）,HF和LF分别降低40%和32.6%;在观测期间火烧处理没有导致土壤CO₂累计排放量的增加。（2）火烧处理下,仅HF处理中土壤呼吸与土壤温度显著相关（P<0.05）,但拟合决定系数较低。（3）单次降水事件会导致火烧处理下土壤呼吸的增加,而对照无明显增加;但连续性降水事件中,降雨早期促进土壤呼吸,而后期呈现出抑制作用。     

多源空间数据整合视角下的城市开发强度研究

城市开发强度能直观表征人类活动强度,对指导城市规划与管理、促进城市可持续发展具有重要价值。采用社会-经济-生态系统耦合视角构建城市开发强度的多维测度体系,整合多源空间数据,测度了杭州市主城及3个副城的开发强度并揭示了其空间分布特征。结果表明,杭州城市开发强度由主城向副城呈波动降低,高强度开发过度集中于主城,主城的功能疏散有待加强;各副城开发强度不一,江南城与主城呈现跨江融合,临平城、下沙城空间上较为独立;各开发维度中,建筑强度、功能强度及效益强度热点区分布基本一致,环境响应高强度区则集聚于主副城交界处,表现出空间异质性。多维测度体系可较好表征城市开发强度,对城市规划及精细化管理具有一定的应用价值。     

DISTRIBUTION AND PHYSIOLOGICAL DETERMINANTS OF BLUE-GREEN ALGAL NITROGEN FIXATION ALONG A THERMOGRADIENT1

The capacity of thermal algal-bacterial mats to fix nitrogen (N₂) was examined in an alkaline thermal stream, Rabbit Creek, of Yellowstone National Park. Nitrogenase activity and nitrogen-fixation rates of mat cores placed in serum bottles and incubated in situ were estimated by the acetylene-reduction technique. Active nitrogenase was not detected at 60 or 65 C in either the blue-green algal or bacterial undermat components of the mats. Acetylene was reduced by all mats ≤55 C along the thermogradient; mean fixation estimates for the mats ranged from 7 to 5,028 nmoles N₂ fixed · mg Chl a^?1· hr^?1. Maximum fixation occurred at 35 C in the stream; statistical comparison of mean rates ordered the thermogradient mats according to estimated activities: 35 > 40 > 30 > 50 ≥ 55 ≥ 45 C. Mats (≤40 C) dominated by species of Calothrix accounted for ca. 97% of the total nitrogen fixation observed in the stream; the remaining activity was associated with mats containing Mastigocladus laminosus Cohn. Light intensity significantly affected fixation rates of the Calothrix mats which responded in a linear fashion from 9–100% full sunlight (ca. 1,900 μEin · m^?2· sec^?1). Calothrix mats from 30 and 40 C had maximum nitrogenase activity at their growth temperature suggesting that nitrogen fixation along the thermogradient was optimally adapted to in situ temperatures.     

Effects of light, temperature, gibberellin (GA3) and their interaction on coleoptile and leaf elongation of tall, semi-dwarf and dwarf wheat

Near-isogenic wheat lines differing in height-reducing (Rht) alleles, in each of two cultivars, were used to investigate the effects of light intensity and of their interaction with temperature and GA₃ application, on the elongation of the coleoptile and the first seedling leaf. Darkness caused a conspicuous increase in the lengths of the coleoptile and of the sheath and lamina of the first leaf, in GA₃ treated and untreated seedlings of all genotypes grown at 11 and 25°C. The genotype effects and the effects of light intensity and GA₃ application on leaf length were ascribed entirely to their effects on the rate of leaf elongation since the duration of leaf elongation was not affected by these factors. Temperature elevation from 11 to 25°C caused a 55% shortening of the duration of leaf elongation and a concomitant increase in elongation rate, which diminished with increased genotypic dwarfness. Accordingly, temperature elevation resulted in a significant reduction in leaf-length of the light-grown dwarf genotypes and the dark-grown dwarf and semi-dwarf genotypes. It is suggested that this temperature × light × genotype interaction effect is due to environmental dependent upper limits of elongation rate set by the Rht alleles.Abbreviations PAR Photosynthetic Active Radiation