克隆整合对遮荫白夹竹分株根际土壤细菌生物特征的影响

克隆整合被认为是克隆植物维持生态优势的重要手段,其通过分株间生理整合缓解资源异质性带来的压力。文章以根状茎克隆植物白夹竹(Phyllostachys bissetii)为研究对象,探讨异质性光照下克隆整合对白夹竹分株根际土壤细菌生物特征的影响。白夹竹克隆片段包含一个近端分株(proximal ramet)和一个远端分株(distal ramet),近端分株或远端分株分别置于80%遮荫环境,另一分株置于全光照环境;同时,分株间根状茎保持连接或割断处理。研究结果表明,不论白夹竹克隆片段近端分株遮荫还是远端分株遮荫,克隆整合均显著促进了遮荫分株根际土壤溶解性有机碳(DOC)含量和微生物生物量碳、氮含量(MBC,MBN);根状茎连接条件下遮荫分株根际土壤胞外N-乙酰基-β-氨基葡萄糖苷酶(NAGase)、脲酶(Urease)活性显著高于根状茎割断处理的遮荫分株;对遮荫分株根际土壤基因组DNA的16S rDNA V3、V4可变区的测序结果表明,可操作分类单元(OTUs)归于13个门,415个属。与根际土壤氮素转化相关的菌群Nitrosomonadaceae(uncultured),Nitrospira,Nitrospinaceae(uncultured),Xanthobacteraceae(uncultured),Bradyrhizobium相对丰度较小(最高值为11.8%)。基于OTUs的主成分分析(PCA)表明,根状茎割断处理并没有对遮荫分株根际土壤细菌生物群落结构产生显著性影响。克隆整合显著促进了遮荫分株根际土壤C有效性,进而刺激了微生物调控的土壤有机质(SOM)周转过程。克隆整合对异质生境下克隆植物土壤细菌生物特征的影响可能部分解释了克隆植物的生态优势。     

光合产物传输方向对蓉城竹根际微生物过程的影响

分株间光合产物的整合作用对克隆植物适应生存环境具有重要作用, 但有关光合产物传输方向对克隆植物根际土壤微生物过程的影响尚不清楚。该研究以根状茎克隆植物蓉城竹(Phyllostachys bissetii)为研究对象, 通过剪除分株地上部分控制光合产物传输方向(顶向传输和基向传输), 研究光合产物传输方向对蓉城竹分株根际土壤微生物过程的影响, 其中顶向传输组是将远端分株地上部分剪除(保留地面以上20 cm), 近端分株自然生长; 基向传输组则是将近端分株地上部分剪除(保留地面以上20 cm), 远端分株自然生长。两组实验中保持根状茎连接或切断处理。测定了地上部分被剪除分株根际土壤中碳和氮有效性、微生物生物量参数以及氮转化相关土壤胞外酶活性等指标。结果表明: 光合产物顶向传输中, 根状茎保持连接的远端分株根际土壤总有机碳(TOC)、溶解性有机碳(DOC)、溶解性有机氮(DON)、铵态氮(NH₄ ⁺-N)、硝态氮(NO₃ ^--N)含量显著高于切断的远端分株, N-乙酰基-β-D-氨基葡萄糖苷酶(NAGase)、多酚氧化酶(POXase)和脲酶(Urease)活性显著升高, 光合产物的顶向传输对远端分株根际碳、氮有效性和根际微生物过程产生了显著性影响; 光合产物的基向传输中, 根状茎保持连接的近端分株根际与切断分株相比具有更高的微生物生物量氮(MBN)含量、Urease、POXase活性, 较低的NAGase活性和NH₄ ⁺-N、NO₃ ^--N含量, 但碳的有效性无显著性差异。蓉城竹分株间光合产物的非对称性传输对根际微生物过程的影响可能是对动物取食或人为砍伐等干扰的有益权衡, 这有助于理解克隆植物对生存环境的种群适应机制。     

Effects of transportation direction of photosynthate on soil microbial processes in the rhizosphere of Phyllostachys bissetii

分株间光合产物的整合作用对克隆植物适应生存环境具有重要作用, 但有关光合产物传输方向对克隆植物根际土壤微生物过程的影响尚不清楚。该研究以根状茎克隆植物蓉城竹(Phyllostachys bissetii)为研究对象, 通过剪除分株地上部分控制光合产物传输方向(顶向传输和基向传输), 研究光合产物传输方向对蓉城竹分株根际土壤微生物过程的影响, 其中顶向传输组是将远端分株地上部分剪除(保留地面以上20 cm), 近端分株自然生长; 基向传输组则是将近端分株地上部分剪除(保留地面以上20 cm), 远端分株自然生长。两组实验中保持根状茎连接或切断处理。测定了地上部分被剪除分株根际土壤中碳和氮有效性、微生物生物量参数以及氮转化相关土壤胞外酶活性等指标。结果表明: 光合产物顶向传输中, 根状茎保持连接的远端分株根际土壤总有机碳(TOC)、溶解性有机碳(DOC)、溶解性有机氮(DON)、铵态氮(NH₄ ⁺-N)、硝态氮(NO₃ ^--N)含量显著高于切断的远端分株, N-乙酰基-β-D-氨基葡萄糖苷酶(NAGase)、多酚氧化酶(POXase)和脲酶(Urease)活性显著升高, 光合产物的顶向传输对远端分株根际碳、氮有效性和根际微生物过程产生了显著性影响; 光合产物的基向传输中, 根状茎保持连接的近端分株根际与切断分株相比具有更高的微生物生物量氮(MBN)含量、Urease、POXase活性, 较低的NAGase活性和NH₄ ⁺-N、NO₃ ^--N含量, 但碳的有效性无显著性差异。蓉城竹分株间光合产物的非对称性传输对根际微生物过程的影响可能是对动物取食或人为砍伐等干扰的有益权衡, 这有助于理解克隆植物对生存环境的种群适应机制。     

异质光环境下克隆整合对白夹竹光合氮分配格局的影响

采用盆栽试验,以单轴散生型竹类植物——白夹竹(Phyllostachys bissetii)克隆片段为对象,使近端分株处于自然光照环境,远端分株处于遮荫环境中,对根状茎作切断或不切断处理,研究克隆整合对远端分株和近端分株光合氮分配格局的影响。结果表明:(1)根状茎保持连接的远端分株较根状茎切断的远端分株具有更高的最大净光合速率、叶片氮含量、光合色素含量、叶片光合氮分配系数。(2)相对根状茎切断处理,根状茎保持连接的远端分株将更多的氮分配到光合系统的羧化系统、生物力能学组分,而分配至捕光系统组分的比例较小。(3)比较处于自然光照条件的近端分株,比叶重、叶片氮含量等并没有因根状茎切断与否表现出显著性差异,根状茎连接的近端分株部分指标甚至高于根状茎切断的近端分株。研究认为,克隆整合作用影响处于遮荫环境的白夹竹远端分株的光合氮分配格局,使得处于遮荫生境中的克隆分株依旧维持较高的光合能力,保证了处于逆境条件下克隆分株的生存与生长。     

杉木人工林土壤微生物群落结构特征

采用氯仿熏蒸法、稀释平板法和磷脂脂肪酸(phospholipid fatty acid,PLFA)方法,分析了常绿阔叶林转变成杉木人工林后土壤微生物种群数量和群落结构的变化特征.结果表明:常绿阔叶林转变为杉木人工林后,林地土壤的微生物生物量碳、可培养细菌和放线菌数降低.杉木人工林地总PLFAs、细菌PLFAs、真菌PLFAs比常绿阔叶林分别降低了49.4％、52.4％和46.6％,革兰氏阳性和阴性细菌PLFAs远低于常绿阔叶林.杉木人工林根际土壤微生物生物量碳、可培养细菌和放线菌数显著高于杉木人工林林地土壤,根际土壤中总PLFAs、细菌PLFAs、革兰氏阳性和阴性细菌PLFAs的含量也高于林地土壤,但真菌PLFAs和细菌PLFAs之比却低于林地土壤.对土壤微生物群落结构进行主成分分析发现,第1主成分和第2主成分共解释了土壤微生物群落结构变异的78.2％.表明常绿阔叶林与杉木人工林土壤的微生物群落结构间存在差异.     

Clonal integration affects growth and sediment properties of the first ramet generation,but not later ramet generations under severe light stress

克隆整合影响严重光胁迫下第一分株世代的生长和沉积物特征但不影响 后续分株世代的生长和沉积物特征 克隆整合通过缓冲环境压力和提高资源获取效率使克隆植物受益。然而,在一个克隆系统中,受益于克隆整合的连接分株世代的数量很少受到关注。我们进行了一个盆栽实验来评估沉水植物苦草 (Vallisneria natans)克隆系统内的生理整合程度,该克隆系统由一个母株和3个依次连接的后代分株组成。 母株生长在正常光照下,而后代分株被严重遮荫。母株与后代分株间的匍匐茎被切断或保持连接,但3个后代分株之间的连接仍然存在。与遮荫的后代分株连接时,苦草未遮荫的母株的光合能力显著增强,但其生物量积累大大减少。克隆整合显著增加了第一分株世代(相邻分株)的生物量积累和土壤的碳氮可用性、胞外酶活性和微生物生物量,但没有增加后续分株世代的这些特征。我们的结果表明,在严重光胁迫下,来自苦草母株的支持可能仅限于克隆系统中相邻的后代分株,这暗示着一个分株世代的效应。我们的结果有助于更好地理解克隆植物的层次结构和分段化。这些发现表明克隆整合程度在分株种群的生态相互作用中起着至关重要的作用。     

芦苇克隆整合对石油污染湿地土壤微生物群落结构和生物量的影响

克隆植物形体相连的无性个体(分株)之间可以进行水分、养分和光合产物的传递和共享,并且这种克隆整合可以显著提高分株对环境胁迫的耐受能力,从而可能进一步影响分株周围的土壤微生物群落结构和生物量。尽管国内外已经开展了大量有关克隆整合对分株耐受胁迫能力影响的研究,但克隆整合对土壤微生物群落结构和生物量影响的研究却十分缺乏。以黄河三角洲芦苇(Phragmites australis)湿地生态系统为研究对象,将直径60 cm的圆形样方进行三个水平的石油添加处理(不添加石油或每年添加5 mm或10 mm厚的石油),同时通过切断或不切断样方内外芦苇根状茎的连接来控制克隆整合的有无。实验连续开展了两年(2014—2015年),每年8月份在样方内进行土壤样品取样,在实验室内采用磷酸脂肪酸(PLFA)法测定土壤微生物总量及主要微生物类群含量,并测定土壤微生物生物量碳和氮含量。取样时间显著影响土壤微生物PLFA总量、微生物碳和氮含量,这3个变量在2015年均显著高于2014年。石油添加在2015年显著增加了土壤微生物PLFA总量,但在2014年却无显著效应;同时,石油添加在2014年降低了土壤微生物碳和氮含量,而在2015年却增加了其含量。然而,无论在2014年还是2015年,芦苇的克隆整合对土壤微生物PLFA含量、微生物碳和氮含量均没有显著影响。土壤微生物PLFA总量与土壤微生物碳和氮含量呈正相关关系。这些结果表明,石油污染可以显著影响湿地土壤微生物动态,但克隆整合却无显著效应。     

川西亚高山不同林龄云杉人工林土壤微生物群落结构

以川西亚高山云杉人工林林地土壤为对象,采用磷脂脂肪酸(PLFA)法研究了4种不同林龄(50、38、27和20年)的人工林土壤微生物多样性和群落结构特征.结果表明: 随着林龄的增加,土壤有机碳和全氮含量逐步增加;土壤微生物Shannon多样性和Pielou均匀度指数则呈现先增后减的趋势.土壤微生物总PLFAs量、细菌PLFAs量、真菌PLFAs量、放线菌PLFAs量以及丛枝菌根真菌PLFAs量均表现为随林龄的增加而增加.主成分分析(PCA)表明,不同林龄人工林的土壤微生物群落结构之间存在显著差异,其中,第1主成分(PC1)和第2主成分(PC2)共同解释了土壤微生物群落结构总变异的66.8%.冗余分析(RDA)表明,对土壤微生物群落结构产生显著影响的环境因子分别为土壤有机碳、全氮、全钾以及细根生物量.随着人工造林时间的延长,土壤肥力和微生物生物量增加,森林生态系统的恢复进程稳定.     

短期CO2浓度升高和干旱胁迫对白羊草土壤碳氮和微生物根际效应的影响

采用人工气候室和盆栽控水试验研究黄土丘陵区典型草本植物白羊草在倍增CO₂浓度(800 μmol·mol^-1)下和充分供水(75%～80%的田间持水量)、轻度干旱胁迫(55%～60%的田间持水量)和重度干旱胁迫(35%～40%的田间持水量)下根际和非根际土壤碳氮含量和微生物群落结构及其根际效应.结果表明: CO₂浓度升高和干旱胁迫对白羊草根际和非根际土壤有机碳、全氮和水溶性有机碳(DOC)含量及其根际效应均无显著影响.轻度干旱胁迫下CO₂浓度升高显著促进了根际土壤水溶性有机氮(DON)的消耗,导致DOC/DON升高,提高了DON的负根际效应和DOC/DON的正根际效应.干旱胁迫和CO₂浓度升高对土壤总磷脂脂肪酸(总PLFA)和细菌PLFA的根际效应无显著影响.CO₂浓度升高条件下干旱胁迫显著提高了根际土壤G⁺/G^- PLFA,降低了非根际土壤G⁺/G^- PLFA,导致其根际效应显著提高,表明根际微生物群落由自养微生物群落向异养微生物群落的转变.     

石油污染盐碱土壤棉花根际微生物与石油烃降解关系

【目的】探讨棉花(Gossypium spp.)生长对石油烃(TPH)污染盐碱土壤微生物群落结构的影响,揭示根际微生物与TPH降解的相关关系。【方法】利用磷脂脂肪酸(PLFA)方法解析根际土壤活性微生物群落随棉花生长的动态变化特征。【结果】根际土壤先后出现了21种PLFAs,包括：饱和脂肪酸(SAT),标识除放线菌之外的细菌;甲基支链末端型饱和脂肪酸(TBSAT),标识除放线菌之外的革兰氏阳性(G+)细菌;标识真菌的多不饱和脂肪酸(PUFA);标识放线菌的甲基支链中间型饱和脂肪酸(MBSAT);标识革兰氏阴性(G?)细菌的单不饱和脂肪酸(MONO)和环丙基脂肪酸(CYCLO)。棉花根际与未栽种棉花的对照(CK)相比,根际土壤微生物PLFAs种类在苗期、蕾期、吐絮期分别增加了100%、83.3%、20.0%,生物量分别增加了53.9%、6.60倍和60.7%;土壤TPH降解率分别提高13.0%、28.0%和30.6%。相关性分析表明：根际土壤TPH降解与根际土壤微生物总生物量具有低度正相关关系(|r|=0.5),但与a14:0、a16:0、i15:0标记的G+细菌生物量高度正相关(|r|≥0.8)。【结论】棉花生长对石油污染盐碱土壤活性微生物群落结构具有显著(p<0.05)的影响,且加速了土壤TPH的降解。该结果将为今后更好地开展石油污染盐碱土壤的生物修复技术研究提供理论依据。     

Clonal integration ameliorates the carbon accumulation capacity of a stoloniferous herb,Glechoma longituba,growing in heterogenous light conditions by facilitating nitrogen assimilation in the rhizosphere

Background and Aims Enhanced availability of photosynthates increases nitrogen (N) mineralization and nitrification in the rhizosphere via rhizodeposition from plant roots. Under heterogeneous light conditions, photosynthates supplied by exposed ramets may promote N assimilation in the rhizosphere of shaded, connected ramets. This study was conducted to test this hypothesis.Methods Clonal fragments of the stoloniferous herb Glechoma longituba with two successive ramets were selected. Mother ramets were subjected to full sunlight and offspring ramets were subjected to 80 % shading, and the stolon between the two successive ramets was either severed or left intact. Measurements were taken of photosynthetic and growth parameters. The turnover of available soil N was determined together with the compostion of the rhizosphere microbial community.Key Results The microbial community composition in the rhizosphere of shaded offspring ramets was significantly altered by clonal integration. Positive effects of clonal integration were observed on NAGase activity, net soil N mineralization rate and net soil N nitrification rate. Increased leaf N and chlorophyll content as well as leaf N allocation to the photosynthetic machinery improved the photosynthetic capability of shaded offspring ramets when the stolon was left intact. Clonal integration improved the growth performance of shaded, connected offspring ramets and whole clonal fragments without any cost to the exposed mother ramets.Conclusions Considerable differences in microbial community composition caused by clonal integration may facilitate N assimilation in the rhizosphere of shaded offspring ramets. Increased N content in the photosynthetic machinery may allow pre-acclimation to high light conditions for shaded offspring ramets, thus promoting opportunistic light capture. In accordance with the theory of the division of labour, it is suggested that clonal integration may ameliorate the carbon assimilation capacity of clonal plants, thus improving their fitness in temporally and spatially heterogeneous habitats.     

To share or not to share: clonal integration in a submerged macrophyte in response to light stress

The ability of clonal plant species to share resources has been studied in many experiments. The submerged macrophyte Potamogeton perfoliatus produces interconnected ramets within short time intervals and hence may or may not share resources with ramets growing in less favourable microhabitats. From a genet point of view, sharing with ramets growing under less favourable conditions might not be an optimal strategy when photosynthates could be used to establish other ramets growing under more favourable conditions. To analyse the plasticity in clonal integration of P. perfoliatus, we set up a factorial aquaria experiment with unshaded or shaded recipient ramets (offspring), which were connected to or separated from donor ramets (parents). Increased biomass production of offspring in parent–offspring systems compared with severed offspring in both light and shade showed that ramets share resources through clonal integration. The relative translocation to the first- and second-offspring generation was influenced by habitat quality: If first-offspring ramets grew in a shaded microhabitat, second-offspring ramets clearly profited. This may be at least partially because of the fact that resources are shifted from first-offspring to second-offspring ramets, indicating controlled senescence of the first-offspring. This complex sharing behaviour might be relevant when plants produce ramets within a dense patch of macrophytes, where support of a shaded ramet might not pay off.     

Physiological integration modifies δ15N in the clonal plant Fragaria vesca,suggesting preferential transport of nitrogen to water-stressed offspring

Background and Aims

One of the most striking attributes of clonal plants is their capacity for physiological integration, which enables movement of essential resources between connected ramets. This study investigated the capacity of physiological integration to buffer differences in resource availability experienced by ramets of the clonal wild strawberry plant, Fragaria vesca. Specifically, a study was made of the responses of connected and severed offspring ramets growing in environments with different water availability conditions (well watered or water stressed) and nitrogen forms (nitrate or ammonium).

Methods

The experimental design consisted of three factors, ‘integration’ (connected, severed) ‘water status’ (well watered, water stressed) and ‘nitrogen form’ (nitrate, ammonium), applied in a pot experiment. The effects of physiological integration were studied by analysing photochemical efficiency, leaf spectral reflectance, photosynthesis and carbon and nitrogen isotope discrimination, the last of which has been neglected in previous studies.

Key Results

Physiological integration buffered the stress caused by water deprivation. As a consequence, survival was improved in water-stressed offspring ramets that remained connected to their parent plants. The nitrogen isotope composition (δ¹⁵N) values in the connected water-stressed ramets were similar to those in ramets in the ammonium treatment; however, δ¹⁵N values in connected well-watered ramets were similar to those in the nitrate treatment. The results also demonstrated the benefit of integration for offspring ramets in terms of photochemical activity and photosynthesis.

Conclusions

This is the first study in which carbon and nitrogen isotopic discrimination has been used to detect physiological integration in clonal plants. The results for nitrogen isotope composition represent the first evidence of preferential transport of a specific form of nitrogen to compensate for stressful conditions experienced by a member clone. Water consumption was lower in plants supplied with ammonium than in plants supplied with nitrate, and therefore preferential transport of ammonium from parents to water-stressed offspring could potentially optimize the water use of the whole clone.     

Effects of Clonal Integration on Microbial Community Composition and Processes in the Rhizosphere of the Stoloniferous Herb Glechoma longituba (Nakai) Kuprian

The effects of rhizodeposition on soil C and N availabilities lead to substantial changes of microbial community composition and processes in the rhizosphere of plants. Under heterogeneous light, photosynthates can be translocated or shared between exposed and shaded ramets by clonal integration. Clonal integration may enhance the rhizodeposition of the shaded ramets, which further influences nutrient recycling in their rhizosphere. To test the hypothesis, we conducted a pot experiment by the stoloniferous herb Glechoma longituba subjected to heterogeneous light. Microbial biomass and community composition in the rhizosphere of shaded offspring ramets, assessed by phospholipid fatty acids (PLFAs) analysis, were markedly altered by clonal integration. Clonal integration positively affected C, N availabilities, invertase and urease activities, N mineralization (N_min) and nitrification rates (N_nitri) in the rhizosphere of shaded offspring ramets. However, an opposite pattern was also observed in phenoloxidase (POXase) and peroxidase (PODase) activities. Our results demonstrated that clonal integration facilitated N assimilation and uptake in the rhizosphere of shaded offspring ramets. The experiment provides insights into the mechanism of nutrient recycling mediated by clonal integration.     

克隆整合和石油污染对芦苇湿地土壤理化性质的影响

克隆整合是克隆植物重要的性状之一。它不仅能够提高分株对环境胁迫的耐受能力,而且可能影响分株周围的土壤属性。为检验克隆整合对土壤属性的影响,在黄河三角洲芦苇湿地开展克隆整合和石油污染的两因子的野外实验。每年将0、5或10 mm厚的原油添加到直径为60 cm的圆形芦苇群落样方内来模拟无污染、轻度或重度石油污染,并通过保留或切断样方内外芦苇根状茎的连接来实现克隆整合的有或无。实验开始于2014年,并于2016年10月采集样方内土壤样品,测定土壤团聚体组成、pH值、电导率、总碳、总氮、总磷和有机碳含量。石油污染显著增加了土壤粗大团聚体(粒径:2 mm)、pH值、总氮和有机碳含量,降低了土壤微团聚体(粒径:0.053—0.25 mm)占比以及电导率。克隆整合显著降低了土壤pH值,提高了土壤电导率和氮磷比。克隆整合和石油污染的交互作用仅对电导率有显著效应。因此,石油污染和克隆整合都可以影响湿地土壤的理化性质,而克隆整合对分株周围土壤理化性质的影响可能进一步影响克隆植物的优势度。     

Trade-offs among growth, clonal, and sexual reproduction in an invasive plant Spartina alterniflora responding to inundation and clonal integration

The purpose of this article was to study the trade-offs among vegetative growth, clonal, and sexual reproduction in an aquatic invasive weed Spartina alterniflora that experienced different inundation depths and clonal integration. Here, the rhizome connections between mother and daughter ramets were either severed or left intact. Subsequently, these clones were flooded with water levels of 0, 9, and 18 cm above the soil surface. Severing rhizomes decreased growth and clonal reproduction of daughter ramets, and increased those of mother ramets grown in shallow and deep water. The daughter ramets disconnected from mother ramets did not flower, while sexual reproduction of mother ramets was not affected by severing. Clonal integration only benefited the total rhizome length, rhizome biomass, and number of rhizomes of the whole clones in non-inundation conditions. Furthermore, growth and clonal reproduction of mother, daughter ramets, and the whole clone decreased with inundation depth, whereas sexual reproduction of mother ramets and the whole clones increased. We concluded that the trade-offs among growth, clonal, and sexual reproduction of S. alterniflora would be affected by inundation depth, but not by clonal integration.