温度对亚热带地区常见树种叶片甲烷排放的影响

以亚热带常见树种米槠、木荷、浙江桂、罗浮栲、杉木和柑橘为对象,利用控制试验研究了温度对树木叶片甲烷(CH4)排放的影响.结果表明:当温度在10℃时,供试的6种树木中,仅木荷、柑橘和罗浮栲的叶片排放CH4;温度高于20℃时,所有树木叶片均可排放CH4.温度高于30℃时,叶片排放CH4的平均排放速率(1.010ngCH4·g-1DM·h-1)是10～30℃时平均排放速率(0.255ngCH4·g-1DM·h-1)的3.96倍.增温对柑橘和杉木CH4排放速率的影响显著高于其他4种树木.培养时间对叶片排放CH4速率有显著影响,温度胁迫对树木排放CH4的影响受植物活性的控制.在低温或高温条件下,树木干叶均不能排放CH4.高温胁迫对树木叶片排放CH4有重要影响,全球变暖可能增加植物的CH4排放.     

一株高产淀粉绿藻——标志链带藻在废水中的培养及对氮磷的去除

为了研究标志链带藻(Desmodesmus insignis strain JNU24)在不同Na NO3浓度和不同废水浓度培养下的生长与代谢产物积累状况,评估标志链带藻对废水的处理能力,本研究利用柱状光反应器对标志链带藻进行培养,分别对4种Na NO3浓度的BG-11培养基和4种废水浓度培养下藻细胞的生物量、蛋白质含量、碳水化合物含量和淀粉含量进行了测定。结果显示,在BG-11培养基中,氮浓度为9.0 mmol/L时,藻细胞生物质浓度最高,达6.23 g/L;在废水培养下,未稀释的原废水实验组,其藻细胞生物质浓度最高,达10.31 g/L;75%废水培养下,藻细胞的淀粉含量最高(达50.9%),单位体积藻细胞淀粉含量和产率分别为4.86 g/L和405 mg·L~(-1)·d~(-1),且显著高于不同浓度Na NO3的BG-11培养基组。本研究还测定了标志链带藻对废水中氮、磷的去除效率,结果显示不同浓度废水培养下,氮、磷的去除效率最高可达90.8%和98.7%。基于柱状反应器中的最佳培养效果,以9.0 mmol/L Na NO3的BG-11培养基和75%废水于3.0 cm光径平板光生物反应器中进行室内扩大培养,结果显示在75%废水培养下,藻细胞生物质浓度达9.75 g/L,淀粉单位体积含量和产率分别达到4.75 g/L和230 mg·L~(-1)·d~(-1),且为9.0 mmol/L Na NO3的BG-11培养基培养的3倍。通过沉降特性分析发现,藻细胞收获90 min后均完全沉降,具有较强的沉降性能。本研究标志链带藻能够耐受废水中较高的氮、磷浓度,且对废水中氮、磷有显著的去除作用;该藻能利用废水中的营养成分积累较高的生物量和淀粉含量并且藻细胞能快速沉降,具有极高的经济价值和应用价值,是一株淀粉生产能力较高和废水处理能力较强的极具开发潜力的藻株。     

变温和恒温对沙葱萤叶甲发育速率的影响

沙葱萤叶甲为近年来在内蒙古草原猖獗成灾的新害虫,为明确温度对其发育速率的影响,分别设置5个变温组合(8/20℃,11/23℃,14/26℃,17/29℃和20/32℃)和6个恒温(13℃,17℃,21℃,25℃,29℃和33℃),比较了变温和恒温对沙葱萤叶甲幼虫和蛹发育速率的影响。结果表明,不同变温组合和恒温对沙葱萤叶甲幼虫和蛹的发育速率有显著的影响。发育历期随温度的升高而缩短,在变温条件下,1龄幼虫期、2龄幼虫期、3龄幼虫期、总幼虫期和蛹期分别从最低温度组合(8/20℃,平均15℃)的11.00,13.44,23.18,46.42和16.89 d,缩短至最高温度组合(20/32℃,平均27℃)的4.92,4.63,9.17,17.83和5.83 d;在恒温条件下,13℃下幼虫不能发育和存活,1龄幼虫期、2龄幼虫期、3龄幼虫期、总幼虫期和蛹期分别从17℃的14.50,10.75,20.63,45.50和11.00 d,缩短至33℃的6.10,5.47,10.60,22.17和5.33 d。在变温条件下,幼虫和蛹的发育起点温度分别为7.44℃和8.48℃,有效积温分别为344.82日度和113.52日度;在恒温条件下,幼虫和蛹的发育起点温度分别为0.64℃和5.11℃,有效积温分别为714.28日度和147.06日度。变温促进了沙葱萤叶甲幼虫和蛹的发育,本研究结果为沙葱萤叶甲的预测预报及综合防控提供了科学依据。     

Responses of growth of four desert species to different N addition levels

Aims The increase in atmospheric N deposition has accelerated N cycling of ecosystems, thus altering the structure and function of ecosystems, especially in those limited by N availability. Studies on the response of plant growth to artificial N addition could provide basic data for a better understanding of how the structure of grasslands in northern China responds to increasing N deposition. Methods We investigated the seasonal dynamics of plant growth of four species after 2-year multi-level N addition in a field experiment conducted in a desert steppe of Ningxia in 2011. Plant biomass and the relative growth rate (RGR) of the studied species were measured and their relationships with C:N:P ratios of plants (community and leaf levels) and soils were analyzed. Important findings Results in 2012 showed that 2-year N addition promoted the growth of the four species and the effects were different among growth forms and were species-specific. In general, the plant biomass of the studied species was significantly correlated with leaf N concentration, leaf N:P ratio, community N pool, soil total N content and soil N:P ratio, while only weak relationships were observed between plant biomass and C:N and C:P ratios of plants and soils. In contrast, there was a significant linear relationship between RGR and N:P ratios both of plants and soils.Our results suggest that short-term N addition promoted the accumulation of plant biomass, and the species-specific responses to stimulated N addition can directly affect the structure of the desert steppe ecosystem. Plant N:P ratio and soil N:P ratio could indicate nutrient limitation of plant growth to a certain extent: N addition increased soil N content and N:P ratio, and thus relieved N limitation gradually. Once more N is available to plants, the growth of plants and the accumulation of community N was stimulated in turn.     

Effects of groundwater salinity on the characteristics of leaf photosynthesis and stem sap flow in Tamarix chinensis

AimsThe objective of this study was to investigate the change pattern of leaves photosynthesis and stem sap flow of Tamarix chinensisin under different groundwater salinity, which can be served as a theoretical basis and technical reference for cultivation and management of T. chinensis in shallow groundwater table around Yellow River Delta.MethodsThree-year-old T. chinensis, one of the dominated species in Yellow River Delta, was selected. Plants were treated by four different salinity concentrations of groundwater—fresh water (0 g∙L^-1), brackish water (3.0 g∙L^-1), saline water (8.0 g∙L^-1), and salt water (20.0 g∙L^-1) under 1.2 m groundwater level. Light response of photosynthesis and the diurnal courses of leaf transpiration rate, stem sap flux velocity and environment factors under different groundwater salinity were determined via LI-6400XT portable photosynthesis system and a Dynamax packaged stem sap flow gauge based on stem-heat balance method, respectively.Important findings The result showed that groundwater salinity had a significant impact on photosynthesis efficiency and water consumption capacity of T. chinensis by influencing the soil salt. The net photosynthetic rate (P_n), maximum P_n, transpiration rate, stomatal conductance, apparent quantum yield and dark respiration rate increased first and then decreased with increasing groundwater salinity, while the water use efficiency (WUE) continuously decreased. The mean P_n under fresh water, brackish water and salt water decreased by 44.1%, 15.1% and 62.6%, respectively, compared with that under saline water (25.90 µmol∙m^-2∙s^-1). The mean WUE under brackish water, saline water and salt water decreased by 25.0%, 29.2% and 41.7%, respectively, compared with that under fresh water (2.40 µmol∙mmol^-1). With the increase of groundwater salinity from brackish water to salt water, light saturation point of T. chinensisdecreased while the light compensation point increased, which lead to the decrease of light ecological amplitude and light use efficiency. Fresh water and brackish water treatment helped T. chinensis to use low or high level light, which could significantly improve the utilization rate of light energy. The decrease in P_n of T. chinensis was mainly due to non-stomatal limitation under treatment from saline water to fresh water, while the decrease in P_n of T. chinensis was due to stomatal limitation from saline water to salt water. With increasing groundwater salinity, stem sap flux velocity of T. chinensis increased firstly and then decreased, reached the maximum value under saline water. The mean stem sap flux velocity under fresh water, brackish water and salt water decreased by 61.8%, 13.1% and 41.9%, respectively, compared with that under saline water (16.96 g·h^-1). Tamarix chinensis had higher photosynthetic productivity under saline water treatment, and could attained high WUE under severe water deprivation by transpiration, which was suitable for the growth of T. chinensis.     

基于Farquhar改进模型的北亚热带森林常见树种光合限速因子研究

为探讨北亚热带地区植物的光合限速因子,利用改进的Farquhar模型研究了9种常见树种的光合特性。结果表明,与常绿树种相比,落叶树种枫香(Liquidambar formosana)和乌桕(Sapium sebiferum)的最大净光合速率(Pmax)和表观羧化速率(CE)较大;核酮糖-1,5-二磷酸羧化酶/加氧酶(Rubisco)活性是他们的光合限速因子。地带性树种青冈栎(Cyclobalanopsis glauca)的Pmax和CE在常绿木本植物中最大,青冈较强的光合能力可能是来源于Vcmax和TPU。耐阴灌木八角金盘(Fatsia japonica)和美人茶(Camellia uraku)的Pmax较小,其光合限速因子是叶肉细胞导度和呼吸速率。低光照下植物较低的光合能力是由于较小的叶肉导度(gm)和TPU导致的;有效光合辐射短时间的降低使得物种的gm平均减少了60.14%。因此,不同树种在不同环境条件下的光合限速因子不尽相同,应根据树种不同的光合生理特性来合理布局,科学育林。     

分析超速离心技术及其在分子生物学中的应用

分析超速离心技术是生物化学和分子生物学中的一种经典方法。该技术是基于热力学和流体动力学第一定律,利用分析超速离心机研究蛋白、核酸和聚合物及其他各种复合物在溶液状态下的行为。从该技术利用的仪器、原理和数据分析方法及其在分子生物学中的应用等方面进行了综述,并对这一技术在现阶段的应用进行了总结和展望,以期为国内相关领域研究人员提供参考。     

尾巨桉液流特征分析

目前尾巨桉( Eucalyptus urophylla × E. grandis)在南部大面积种植,尤其是在广西,其水分利用效率对森林可持续发展和水资源管理的影响越来越受到关注,因此了解其水分利用特征具有一定的意义。该文通过Granier热扩散探针法(TDP)对广西黄冕国有林场4~5年生尾巨桉人工林液流密度(SFD)的年变化规律、不同个体变化及其与环境因子的关系进行了研究。结果表明：尾巨桉年平均日液流密度为830.1 L.m-2.d-1;从尾巨桉日液流密度的年变化来看,最大值不超过2000 L.m-2.d-1,与相似研究比较,该研究得到的结果偏低。不同直径尾巨桉SFD具有相似的变化趋势,胸径相近其液流密度也大致相同,但胸径相差很大时,其液流密度相差也大,相差最大可达1300 L.m-2.d-1,这主要与不同生长状况的植物根系从土壤吸收水分能力不同有关。相关研究表明光合有效辐射和水汽压亏缺是树木冠层蒸腾的主要动力,该研究也发现树干液流密度与水汽压亏缺( VPD)、光合有效辐射( PAR)在年变化上有很好的同步性,主要表现出夏秋季节较高、春冬季节较低的现象。 SFD与PAR的关系比较显著,与VPD、空气温度( AT)、土壤温度( ST)有一定的关系,但与空气相对湿度( RH)和土壤湿度( SM)没有呈现规律。环境因子和植物生物学特征是树干液流密度主要的影响因素,进一步探讨尾巨桉如何响应这些因子的变化显得尤为重要。     

不同二氧化碳浓度培养对两株栅藻碳固定速率及油脂积累的影响

正人类在利用化石燃料的过程中会导致大量有害温室气体CO_2的排放,促进全球气候变暖。微藻可通过光合作用固定CO_2,同时大量的微藻生物质还能作为生物能源的原料[1],因此,越来越多的研究关注于微藻生物固碳以达到降低碳排放的目的。利用微藻光合作用进行CO_2固定是一种能量节约型和环境友好型技术手段[2]。在利用微藻进行CO_2生物固定以及生物燃料生产时,研究微藻的CO_2固定能力、CO_2对微藻的生长以及油脂积累的影响等都是十分重要的。国内外利用微藻进行生     

泥沙埋深对苦草和微齿眼子菜及两物种混合分解的影响

为探讨泥沙淤积对水生植物分解的影响,研究了沉水植物苦草(Vallisneria natans)、微齿眼子菜(Pota-mogeton maackianus)及两物种混合在底泥中不同埋深(0 和5 cm)的分解速率和养分动态,实验周期为117d。结果显示:(1)在0和5 cm埋深处理下,苦草、微齿眼子菜及两物种混合的分解速率均表现为苦草最快,微齿眼子菜最慢,物种混合介于两单种之间。与0 cm处理相比,在5 cm埋深处理下苦草、微齿眼子菜及两物种混合的分解速率显著降低(P0.05)。苦草在0和5 cm埋深处理下分解35天后干重剩余率分别为0和43.51%、在5 cm处理下分解82d后干重剩余率为0。微齿眼子菜和两物种混合在5 cm埋深处理下分解117d后的干重剩余率分别提高了31.09%和37.44%。(2)与0 cm处理相比,5 cm埋深处理显著抑制苦草、微齿眼子菜及两物种混合的N、P释放。苦草在0和 5 cm埋深处理下分解35天后N剩余率分别为0和31.28%、P剩余率分别为0和24.45%。在5 cm埋深处理下分解117天后微齿眼子菜N和P剩余率分别提高了19.45%和14.73%、两物种混合N、P剩余率分别提高了41.57%和22.82%。(3)两物种混合在0和5 cm埋深处理下,其分解速率均表现为加和效应,但N、P元素释放在0 cm处理下分别表现为协同效应和加和效应,在5 cm埋深处理下均表现为拮抗效应。(4)随着分解的进行,5 cm埋深处理下的苦草和微齿眼子菜的微生物呼吸速率均显著降低,物种混合的微生物生物量始终低于0 cm处理。这些结果表明泥沙埋深显著降低了苦草、微齿眼子菜及两物种混合的分解速率和N、P元素释放,物种混合的N、P元素释放在分解后期均因沉积作用而产生了拮抗效应。此外,泥沙埋深对分解的抑制作用与微生物呼吸及生物量降低有密切的关系。研究结果可为认识水生植物分解对沉积作用的响应机制提供资料,并为了解水生植物分解对底质营养动态的影响提供参考。