Provenance effect on carbon assimilation,photochemistry and leaf morphology in Mediterranean Cistus species under chilling stress

• The potential resilience of shrub species to environmental change deserves attention in those areas threatened by climate change, such as the Mediterranean Basin. We asked if leaves produced under different climate conditions through the winter season to spring can highlight the leaf traits involved in determining potential resilience of three Cistus spp. to changing environmental conditions and to what extent intraspecific differences affect such a response.
• We analysed carbon assimilation, maximum quantum efficiency of PSII photochemistry (F_v/F_m) and leaf morphological control of the photosynthetic process in leaves formed through the winter season into spring in C. creticus subsp. eriocephalus (CE), C. salvifolius (CS) and C. monspeliensis (CM) grown from seed of different provenances under common garden conditions.
• Intraspecific differences were found in F_v/F_m for CE and CS. Carbon assimilation‐related parameters were not affected by provenance. Moreover, our analysis highlighted that the functional relationships investigated can follow seasonal changes and revealed patterns originating from species‐specific differences in LMA arising during the favourable period.
• Cistus spp. have great ability to modify the structure and function of their leaves in the mid‐term in order to cope with changing environmental conditions. The F_v/F_m response to chilling reveals that susceptibility to photoinhibition is a trait under selection in Cistus species. Concerning carbon assimilation, differing ability to control stomatal opening was highlighted between species. Moreover, seasonal changes of the functional relationships investigated can have predictable consequences on species leaf turnover strategies.

     

氮稳定同位素技术在陆地生态系统氮循环研究中的应用

在过去几十年中, 氮(N)稳定同位素技术的发展提高了人们对于陆地生态系统氮循环的认识。该文回顾了氮稳定同位素技术在研究生态系统氮循环中的历史, 综述了最近十多年来氮稳定同位素技术在陆地生态系统氮循环研究中的典型案例, 包括利用氮同位素自然丰度鉴定植物氮来源、指示生态系统氮状态和量化过程速率, 利用¹⁵N标记技术示踪氮的去向和再分布等。该文同时指出这些应用中存在的问题, 以及在陆地生态系统上氮稳定同位素技术今后研究的重点发展方向。     

土壤剖面碳氮稳定同位素自然丰度的垂直分布模式及其影响机制

土壤碳、氮稳定同位素自然丰度(δ13C和δ15N)随土壤深度变化的研究,对揭示碳、氮元素生物地球化学循环机制具有重要意义.本文在概述土壤剖面δ13C和δ15N垂直分布特征的基础上,重点介绍了土壤δ13C和δ15N垂直分布模式的影响机制.土壤剖面δ13C垂直分布模式的影响机制主要有3种:1)植被δ13C值的历史变化;2)...     

Differential CO2 effect on primary carbon metabolism of flag leaves in durum wheat (Triticum durum Desf.)

C sink/source balance and N assimilation have been identified as target processes conditioning crop responsiveness to elevated CO₂. However, little is known about phenology‐driven modifications of C and N primary metabolism at elevated CO₂ in cereals such as wheat. Here, we examined the differential effect of elevated CO₂ at two development stages (onset of flowering, onset of grain filling) in durum wheat (Triticum durum, var. Sula) using physiological measurements (photosynthesis, isotopes), metabolomics, proteomics and ¹⁵N labelling. Our results show that growth at elevated CO₂ was accompanied by photosynthetic acclimation through a lower internal (mesophyll) conductance but no significant effect on Rubisco content, maximal carboxylation or electron transfer. Growth at elevated CO₂ altered photosynthate export and tended to accelerate leaf N remobilization, which was visible for several proteins and amino acids, as well as lysine degradation metabolism. However, grain biomass produced at elevated CO₂ was larger and less N rich, suggesting that nitrogen use efficiency rather than photosynthesis is an important target for improvement, even in good CO₂‐responsive cultivars.     

太湖沉积物有机碳与氮的来源

选取太湖梅梁湾和湖心柱状沉积物,研究了其有机碳同位素（δ13C）和氮同位素（δ15N）、C/N、总有机碳(TOC)、总氮(TN)、总磷（TP）含量,并结合210Pb和137Cs沉积物年代测定技术,探究了近百年太湖沉积物有机质和氮的来源。结果表明：太湖梅梁湾湖区在近百年来,其有机质来源总体以自生为主。50年代以前,湖区受到人类活动的影响较小,沉积物有机质主要来自于湖泊自身水生植物的沉积;50年代到70年代,湖泊内部环境发生变化,湖区逐渐出现藻类大量死亡并沉积的现象,有机质主要来自于水生植物和藻类的共同沉积;70年代到80年代沉积物机质藻类贡献进一步增大;90年代后到现在,则以藻类的沉积为主要来源方式。梅梁湾湖区沉积物氮素的来源在50年代以前主要以流域土壤流失和大型水生植物的死亡为主;50年代到70年代,人类活动的加剧导致大量工业废水、生活污水的输入,藻类开始大面积爆发,氮主要来自于外源的输入、大型植物和藻类的死亡沉积;90年代后到现在,外源氮的输入得到有效地控制,藻类对沉积物氮的贡献相对显著。湖心区域沉积物有机质和氮的来源主要来自于湖泊内部水生植物的沉积。70年代前,沉积物有机质和氮的来源主要来自于水生植物的沉积和水土流失作用;70年代至今,虽然湖泊受到人类活动外源物质输入影响逐渐增大,但总体来讲贡献较小,沉积物有机质和氮的来源仍以湖泊自生为主。     

Enhanced formation of methane in plant cell cultures by inhibition of cytochrome c oxidase

The claim of methane (CH₄) formation in plants has caused much controversy and debate within the scientific community over the past 4 years. Here, using both stable isotope and concentration measurements, we demonstrate that CH₄ formation occurs in plant cell cultures that were grown in the dark under sterile conditions. Under non‐stress conditions the plant cell cultures produced trace amounts [0.3–0.6 ng g^?1 dry weight (DW) h^?1] of CH₄ but these could be increased by one to two orders of magnitude (up to 12 ng g^?1 DW h^?1) when sodium azide, a compound known to disrupt electron transport flow at the cytochrome c oxidase (complex IV) in plant mitochondria, was added to the cell cultures. The addition of other electron transport chain (ETC) inhibitors did not result in significant CH₄ formation indicating that a site‐specific disturbance of the ETC at complex IV causes CH₄ formation in plant cells. Our study is an important first step in providing more information on non‐microbial CH₄ formation from living plants particularly under abiotic stress conditions that might affect the electron transport flow at the cytochrome c oxidase in plant mitochondria.     

Tracing prey origins,proportions and feeding periods for predatory beetles from agricultural systems using carbon and nitrogen stable isotope analyses

Predatory beetles are an important component of the natural enemy complex that preys on insect pests such as aphids within agroecosystems. Tracing diet origins and movement of natural enemies aids understanding their role in the food web and informs strategies for their effective conservation. Field sampling and laboratory experiments were carried out to examine the changes of carbon and nitrogen stable isotope ratios (δ¹³C and δ¹⁵N) among crops (cotton and maize), pests (cotton and maize aphids), and between wing and abdomen of predatory beetles, Propylea japonica, and to test the hypothesis that prey origins, proportions and feeding periods of the predatory beetles can be deduced by this stable isotope analysis. Results showed that the δ¹³C values both in wing and abdomen of adult P. japonica were changing from a C₃- to a C₄-based diet of aphids reared on maize or cotton, respectively; the isotope ratio of their new C₄ substrates were detectable within 7 days and the δ¹⁵N values began to reflect their new C₄ substrates within 3 days. The relationship between δ¹³C and δ¹⁵N values of P. japonica adults in wing or abdomen and diets of aphids from a C₃-based resource transitioning to a C₄-based resource were described best in linear or quadratic equations. Results suggest that integrative analysis of δ¹³C and δ¹⁵N values can be regarded as a useful method for quantifying to trace prey origins, proportions of diets and feeding periods of natural enemies. The results can provide quantifying techniques for habitat management of natural enemies.     

自养微生物同化CO_2的分子生态研究及同化碳在土壤中的转化

大气中CO2浓度持续升高和全球气候变暖是亟待解决的重大环境问题。自养微生物在环境中广泛分布,能直接参与CO2的同化,因此研究自养微生物同化CO2的分子生态学机制具有重大的科学意义。以往对自养微生物的研究多针对基因组DNA,从DNA水平揭示了不同生态系统中碳同化自养微生物的种群结构和多样性,但这些微生物在生态系统中的具体功能有待进一步的研究。近年来,随着转录组学研究技术和稳定同位素探针技术(SIP)的发展,自养微生物同化CO2的生态机理研究不断深入,这些研究明确揭示了碳同化自养微生物是河流、湖泊和海洋生态系统中CO2固定作用的驱动者,并新发现了一些具有CO2同化功能的微生物群落。基于国内外有关研究进展,从DNA和RNA水平上对自养微生物同化CO2的分子机理以及稳定同位素探针技术(SIP)在碳同化微生物研究中的应用进行了分析和总结,初步展望了RNA-SIP技术在陆地生态系统碳同化微生物分子生态学研究中的前景。同时,探讨了陆地生态系统同化碳的转化和稳定性机理,以期为深入了解生态系统碳循环过程和应对气候变化提供理论依据。     

预处理及保存方法对浮游动物碳、氮稳定同位素比值的影响

研究了不同预处理及保存方法对浮游动物碳、氮稳定同位素比值的影响.结果表明:未清养的舌状叶镖水蚤PhyHodiaptomus tunguidus与清养3h的相比δ¹³C和δ¹⁵N的差异均不显著,但肠道内含物造成了重复样品间的较大偏差;去除脂肪后的舌状叶镖水蚤δ¹³C和δ¹⁵N均显著升高;经甲醇保存后,舌状叶镖水蚤和奥氏秀体溞Diaphanosoma orghidani transamurensis的δ¹³C均有所升高,但不显著;经乙醇保存后,舌状叶镖水蚤δ¹³C显著升高,而奥氏秀体溞的δ¹³C也有所升高但不显著;经过甲醛保存后,舌状叶镖水蚤和奥氏秀体溞的δ¹³C降低,但不显著;冰冻保存使奥氏秀体溞的δ¹³C显著降低,而使舌状叶镖水蚤的δ¹³C也有所降低但不显著.四种保存方法对舌状叶镖水蚤和奥氏秀体溞的δ¹⁵N都没有显著影响.在进行不同研究间的比较时,必须考虑样品保存与处理方法造成的差异.同时,食物网结构的稳定同位素研究有待建立统一的样品保存与处理方法.     

四川裂腹鱼耳石碳、氧稳定同位素特征

为探讨耳石碳(δ¹³C)、氧(δ¹⁸O)稳定同位素在淡水鱼类群体识别中的作用,本研究以养殖条件下不同年龄组四川裂腹鱼为对象,采用稳定同位素质谱仪进行碳、氧同位素测定,揭示耳石中碳、氧稳定同位素特征,探讨其与环境间的关系. 结果表明:1⁺龄四川裂腹鱼δ¹³C和δ¹⁸O值均与耳石质量无显著相关关系,但在微耳石和星耳石之间存在显著差异;不同年龄四川裂腹鱼微耳石δ¹³C和δ¹⁸O平均值分别为(-9.58±0.06)‰、(-8.33±0.17)‰,其在雌雄个体之间均无显著性差异,但在不同年龄组间存在显著差异. 耳石δ¹⁸O和δ¹³C的关联分析能有效区分四川裂腹鱼不同养殖年龄群体,可作为一种识别淡水鱼类养殖群体的手段.     

水生动物碳氮稳定同位素富集系数的整合分析

同位素富集系数即动物组织与其食物之间同位素丰度（δ）的差异值(Δ),是稳定性同位素技术应用于生态系统营养关系、食性和食物网研究的重要参数.不同生境条件下和不同物种之间的富集系数通常被认为是相对稳定的,但越来越多的研究发现,富集系数在不同类型动物之间存在明显差异而不是一个恒定值,尽管这一差异范围仍不清楚.本文进行了3种不同权重设置方式的整合分析,综述并比较了4类水生动物(硬骨鱼类、甲壳类、爬行类、软体动物)的碳氮稳定同位素富集系数.在Web of Science和CNKI数据库上搜索2014年底之前发表的论文,获得了42篇包含140个Δ¹³C的研究结果和159个Δ¹⁵N的研究结果.使用3种不同的加权方式进行3次独立整合分析,3种加权方式分别是以方差倒数作为权重、以样本量作为权重和相等权重.结果表明,整合分析统计结果十分稳健,不同权重设置的分析结果差异很小.水生动物碳稳定同位素富集系数(Δ^13C)总体平均值为1.0‰,其中,硬骨鱼类1.0‰,甲壳类1.3‰,爬行类0.5‰,软体动物1.5‰;氮稳定同位素富集系数(Δ¹⁵N)总体平均值为2.6‰,其中,硬骨鱼类2.4‰,甲壳类3.6‰,爬行类1.0‰,软体动物2.5‰.统计分析表明,硬骨鱼类、甲壳类、爬行类、软体动物之间的Δ¹³C没有显著差异,而Δ¹⁵N存在显著差异.因此,应用稳定性同位素技术研究水生动物营养关系、食性和食物网中碳富集系数可以选择总体平均值,而氮富集系数则应根据不同水生动物类型选取相应的系数值.     

基于稳定同位素技术的长湖鱼类营养结构研究

本研究应用碳、氮稳定同位素技术分析了2017年秋季（10月）和2018年春季（3月）湖北省荆州长湖鱼类营养结构特征,构建了δ¹³C和δ¹⁵N稳定同位素双位图,并计算了7个相关的量化指标。结果显示：所采集的16种鱼类,δ¹³C均值范围为（-27.7±0.8）‰~（-24.8±0.1）‰,δ¹⁵N的均值范围为（11.4±0.3）‰~（16.6±0.5）‰。营养生态位分析显示,长湖鱼类以偏肉食性鱼类黄颡鱼的营养级最高（3.28±0.2）,草鱼的营养级最低（1.74±0.1）。稳定同位素的量化指标表明,长湖春季鱼类群落核心生态位空间（standard ellipse area, SEA）、生态位总空间（total area, TA）和基础食物来源（δ¹³C range, CR）均高于秋季,两个季度的营养多样性（centrifugal distance, CD）和鱼类群落的整体密度（mean nearest neighbor distance, MNND）相似,但春季的营养长度（δ¹⁵N range, NR）和鱼类群落营养生态位分布范围（standard deviation of nearest neighbor distance, SDNND）值低于秋季。说明春季长湖的生态位总空间（TA上升）和基础食物来源（CR上升）较为丰富,但因鱼类种类的食性相近,其群落的总食物链降低（NR下降）。该研究可为分析拆围后长湖鱼类群落结构特征积累基础数据,也为长湖的渔业管理策略提供依据。     

贵州白云岩地区植物群落叶片-凋落物-土壤化学计量与碳氮同位素特征

剖析天然次生林生态化学计量与C、N同位素丰度的关系,能够阐明元素平衡对同位素分馏的影响规律,深刻揭示生态系统资源分配机制与利用策略。以贵州白云岩地区马尾松林(Pinus massoniana forest)、山胡椒林(Lindera glauca forest)、烟管荚蒾林(Viburnum utile forest)、化香林(Platycarya strobilacea forest)和白栎林(Quercus fabri forest)为对象,厘清叶片-凋落物-土壤连续体的生态化学计量特征与C、N同位素丰度及其内在关联。结果表明：(1)不同群落叶片、凋落物、土壤C、N、P含量存在差异,总体为叶片>凋落物>土壤,N在连续体间的继承性较强,C则较弱。(2)不同植物群落连续体间C∶N、C∶P、N∶P差异显著,5种群落均受到N元素限制,化香林和白栎林还受P限制;烟管荚蒾林C∶N、C∶P与化香林N∶P显著性较高,植物通过协调化学计量平衡以满足自身生长发育和适应环境的需求。(3)叶片、凋落物、土壤δ¹³C分别为-32.45‰—-29.22‰、-30.11‰—-2...     

若尔盖草甸退化对土壤碳、氮和碳稳定同位素的影响

为了解不同退化阶段高寒草甸土壤碳、氮和碳稳定同位素的差异,对若尔盖湿地内沼泽草甸、草原化草甸、退化草甸3个阶段土壤的碳、氮和碳稳定同位素进行了分析.结果表明:若尔盖湿地草甸土壤δ¹³C 值介于-26.21‰～-24.72‰之间,土壤δ¹³C 值随土层加深而增大.土壤δ¹³C 值与有机碳含量对数值呈线性负相关.表层土壤(0～10 cm)δ¹³C值大小顺序为草原化草甸>退化草甸>沼泽草甸,β值大小顺序为草原化草甸>沼泽草甸>退化草甸.沼泽草甸、草原化草甸、退化草甸0～30 cm 土壤碳含量分别为105.32、42.11和31.12 g·kg^-1,氮含量分别为8.74、3.41和2.81 g·kg^-1,C/N分别为11.26、11.23和10.89.随着草甸的退化,土壤碳、氮呈降低趋势,退化草甸C/N值低于沼泽草甸和草原化草甸.随着土层深度加深,碳、氮含量呈现降低趋势.草甸退化导致的土壤δ¹³C 值差异主要发生在表层0～10 cm.3个退化阶段中,退化草甸土壤的β值和C/N最低,表明退化草甸土壤矿化作用较强.     

Stable carbon and nitrogen ratios in the sand smelt from a Mediterranean coastal area: feeding habits and effect of season and size

Enriched δ¹³C values (annual average – 11.2‰) suggest that in the study site (Stagnone di Marsala, Italy) the sand smelt Atherina boyeri exploited benthic prey throughout the year. In particular, Mysidacea and Isopoda seemed to dominate the diet. Stomach content data from the literature was in partial agreement with the present isotopic analysis suggesting that, while Mysidacea and Isopoda are exploited by A. boyeri , Copepoda Harpacticoida and Amphipoda are the dominant food items of the sand smelt diet. Several hypotheses are proposed to explain such partially different results from the two techniques. Both season and size influenced the δ¹³C and δ¹⁵N values of A. boyeri . Although throughout the sampling year, A. boyeri showed very enriched δ¹³C and δ¹⁵N values consistent with a diet based on benthic resources, it showed significant seasonal differences in both nitrogen and carbon isotope ratios. Such a finding suggests that the food preferences of A. boyeri undergo small seasonal differences, probably as a consequence of prey availability. Size also affected the isotopic composition of the sand-smelt indicating that this species shows ontogenetic diet shifts in the study site. Compared with other Mediterranean trophic data of the sand smelt these results substantiate the great adaptability of A. boyeri to the local environmental resources and its trophic plasticity.     

The Nostoc-Gunnera symbiosis: carbon fixation and translocation

The in vitro specific activity of ribulose-1,5-bisphosphate carboxylase (Rubisco; EC 4. 1. 1. 39) and the dark and light in vivo CO₂ fixation activities were determined in the cyanobiont of Gunnera . Compared to the free-living isolate Nostoc PCC 9231, the in vitro Rubisco activity was high, while the in vivo CO₂ fixation was very low. Light did not significantly influence CO₂ fixation if the cyanobiont was left in the sliced Gunnera tissues, while a small light stimulation was found for CO₂ fixation of the freshly-isolated cyanobiont. The adjacent non-infected Gunnera tissue showed a very low CO₂ fixation. A rapid translocation of fixed ¹⁴CO₂ from leaves towards apical parts of the plant was apparent, in particular to the symbiotic tissue. The ¹⁴C label appeared mainly in soluble form in this tissue and was rapidly catabolised as shown by ¹⁴C chase experiments. Also, short-term experiments revealed that maximum ¹⁴C accumulation occurred in the symbiotic tissue showing the highest rates of nitrogen fixation (Söderbäck et al. 1990), about 10–15 mm from the plant apex. The data were taken to indicate that there is a modification in the photosynthetic light reaction of the cyanobiont and that the cyanobiont lives heterotrophically in the dark on photo-synthate rapidly delivered from nearby leaves of the host plant.     

人为营养物质输入对汉丰湖不同营养级生物的影响--稳定C、N同位素分析

以长江一级支流小江上游的汉丰湖为研究对象,设置了4个采样点(影响组:A, B;对照组:C, D),应用碳、氮稳定性同位素探讨人类生活污水和农业面源污染对汉丰湖水生生态系统中不同营养级水平生物类群的影响。结果表明:影响组POM(颗粒有机物)和螺类碳、氮稳定性同位素比值范围分别为-25.93‰--24.63‰、4.12‰-9.86‰,-14.28‰--21.60‰、7.97‰-19.99‰;对照组POM(颗粒有机物)和螺类碳、氮稳定性同位素比值范围分别为-25.62‰--22.51‰、0.01‰-6.56‰,-22.96‰--19.21‰、6.75‰-8.89‰;不同组间POM和初级消费者螺类碳同位素比值无明显空间变化(P>0.05), 而氮稳定性同位素比值空间变化显著(P<0.05)。因此,在汉丰湖食物网中,氮稳定性同位素特征更好地反应了营养物质(人为输入)吸收和富集的信息。与固着藻类、鱼类等相比,POM和软体动物螺类更适合作为环境评价的指示物。影响组A、B样点的部分生物类群已经受到了人为营养物质输入的影响,影响强度B样点区域>A样点区域。结果建议加强汉丰湖水环境保护,控制污水排放量及提高污水处理水平,对于保护小江和三峡库区水质具有十分重要的意义。