Caracterização das estratégias ecofisiológicas de samambaias em resposta à inundação na restinga de Maricá, Rio de Janeiro, Brasil

As matas inundáveis e brejos presentes nas restingas desencadeiam uma série de processos que influenciam as características físico-químicas e biológicas do solo, levando as plantas a apresentarem mecanismos de aclimatação ou adaptação ao estresse da inundação, como alterações morfológicas e fisiológicas de forma a minimizar os efeitos da falta de oxigênio. Dentre as espécies vegetais de samambaias ocorrentes em ambientes inundáveis nas restingas, se destacam três espécies: Acrostichum danaeifolium Langsd. & Fisch., Blechnum serrulatum Rich. e Thelypteris interrupta (Willd.) K.Iwats. O objetivo deste trabalho é caracterizar os aspectos ecofisiológicos que os esporófitos dessas samambaias apresentam para sobreviver em ambientes de inundação na restinga de Maricá, estado do Rio de Janeiro. Neste sentido, foi determinada a caracterização física e química dos sítios de ocorrências destas samambaias, as variações foliares entre elas, espessura, densidade, massa por unidade de folha, teor de clorofilas e atributos quantitativos das células epidérmicas, além da quantificação e determinação à distribuição dos carboidratos. Para as variáveis dos vegetais foram feitas coletas na estação chuvosa e seca e para variáveis do solo na estação seca. Os sítios analisados se mostraram extremamente ácidos, de baixa fertilidade e com toxidez por macro e micro nutrientes, indicando que as samambaias apresentam tolerância a estes fatores. Na época chuvosa (inundação), as samambaias apresentaram queda na densidade foliar, acompanhada de um aumento de massa por unidade de folha. Esta habilidade de conseguir ganhar massa seca por área classifica todas as samambaias analisadas como tolerantes à inundação. Os altos valores de carboidratos solúveis nas folhas indicam aumento da degradação do amido foliar e o menor teor de carboidrato solúvel encontrado nos caules explicita a redução na respiração das raízes destas plantas sob anoxia/ hipoxia, para evitar a oxidação e o incremento do estoque de amido de reserva, elucidando estratégia de tolerância à inundação. A menor disponibilidade de água na estação seca afeta diretamente os atributos foliares diminuindo o índice estomático, a suculência e a massa por unidade de folha, no qual reflete na queda das concentrações de clorofilas. Os menores valores nas concentrações de clorofila têm influencia direta na presença de amidos foliar que são estocado e, alterando toda a dinâmica dos carboidratos nestas espécies. A análise do sítio onde cresce Acrostichum danaeifolium indica níveis críticos de Na no solo e provavelmente, a produção de mucilagem no caule e no pecíolo é uma estratégia de tolerância ao ambiente salino e inundado. O elevado índice de cobertura de Blechnum serrulatum em ambientes inundados indica que esta espécie possui adaptações a solos hidromórficos, entre elas, grande capacidade de estocagem de amido no caule. A maior sinuosidade das células epidérmicas em T. interrupta permite uma alta suculência mantendo o status hidrológico da folha em ambas as estações. Os resultados apresentados, além de agregar informações sobre a biologia das samambaias nos neotrópicos, irão contribuir para a compreensão da dinâmica de ocupação de espécies herbáceas em ambientes alagáveis nas restingas brasileiras

Physiological Determinants of Invasive Success Linking Distribution Patterns to Metabolic Physiology in Native and Invasive Blue Mussels (genus Mytilus)

In the early 20th century, a blue mussel species from the Mediterranean invaded the California coast and subsequently out-competed the native species south of Monterey Bay. Like other invasive species, Mytilus galloprovincialis has physiological traits that make it successful in habitats formerly occupied by the native M. trossulus, namely its adaptation to warm sea surface temperatures. This study looks at the current genotype distributions and enzymatic activities of field-acclimatized mussels within the hybrid zone where the species co-occur as well as mussels that have been acclimated for four weeks to different temperature and salinity conditions. In the field-acclimatized and laboratory-acclimated mussels, the native species exhibited significantly higher enzyme rates, which may reflect an evolutionary adaptation to compensate to low habitat temperatures. Indeed, the results of the laboratory acclimation indicate that these differences are genetically based. Whether an acclimation capacity exists may require even longer-term acclimation to different temperatures. Current findings suggest that the further spread of the invasive species is likely to be governed in large measure by the potentially counteracting effects of rising temperatures, which would favor the northerly spread of M. galloprovincialis, and increased winter precipitation, which would favor the persistence of M. trossulus. However, the success of M. galloprovincialis during acclimation to ‘dilute’ salinity (25 ppt) suggests that the invasive species can tolerate a greater salinity range than previously thought. Thus, further investigation is needed to build a comprehensive predictive model of the movement of M. galloprovincialis and the hybrid zone along the California coast.

Anadromous fish as marine nutrient vectors

The tidal freshwater of Virginia supports anadromous herring (Alosa spp.) spawning runs in the spring; however, their importance as nutrient delivery vectors to the freshwater fish food web remains unknown. The stable isotope signatures of fishes from 21 species and four different guilds (predators, carnivores, generalists, and planktivores) were examined in this study to test the hypothesis that marine derived nutrients (MDNs) brought by anadromous fish would be traced into the guilds that incorporated them. Spawning anadromous fish were 13C and 34S-enriched (δ13C and δ34S of approximately 18‰ and 17.7‰, respectively) relative to resident freshwater fish. Of the guilds examined, only predators showed 13C and 34S-enrichment similar to the anadromous fish; however, some generalist catfish also showed enriched signatures. Specific fatty acid δ13C signatures for gizzard shad (Dorosoma cepedianum), blue catfish (Ictalurus furcatus), and alewife (Alosa pseudoharengus), show a 10‰ range among fishes, clearly reflecting isotopically distinct dietary sources. The δ13C and δ34S distribution and range among the freshwater fishes suggest that both autochthonous and allochthonous (terrestrial C3 photosynthetic production and MDN) nutrient sources are important to the tidal freshwater fish community.

Early response to nanoparticles in the Arabidopsis transcriptome compromises plant defence and root-hair development through salicylic acid signalling

Background: The impact of nano-scaled materials on photosynthetic organisms needs to be evaluated. Plants represent the largest interface between the environment and biosphere, so understanding how nanoparticles affect them is especially relevant for environmental assessments. Nanotoxicology studies in plants allude to quantum size effects and other properties specific of the nano-stage to explain increased toxicity respect to bulk compounds. However, gene expression profiles after exposure to nanoparticles and other sources of environmental stress have not been compared and the impact on plant defence has not been analysed. Results: Arabidopsis plants were exposed to TiO2-nanoparticles, Ag-nanoparticles, and multi-walled carbon nanotubes as well as different sources of biotic (microbial pathogens) or abiotic (saline, drought, or wounding) stresses. Changes in gene expression profiles and plant phenotypic responses were evaluated. Transcriptome analysis shows similarity of expression patterns for all plants exposed to nanoparticles and a low impact on gene expression compared to other stress inducers. Nanoparticle exposure repressed transcriptional responses to microbial pathogens, resulting in increased bacterial colonization during an experimental infection. Inhibition of root hair development and transcriptional patterns characteristic of phosphate starvation response were also observed. The exogenous addition of salicylic acid prevented some nano-specific transcriptional and phenotypic effects, including the reduction in root hair formation and the colonization of distal leaves by bacteria. Conclusions: This study integrates the effect of nanoparticles on gene expression with plant responses to major sources of environmental stress and paves the way to remediate the impact of these potentially damaging compounds through hormonal priming.

Dinâmica de crescimento em Tabebuia rosea (Bertol.) Bertero ex A.DC. (Bignoniaceae): fenologia apical e cambial caulinar

O estudo da dinâmica de crescimento em espécies arbóreas permite melhor compreender a adaptação de uma espécie ao ambiente em que se desenvolve. Dados dessa natureza ainda são escassos no Brasil considerando-se a diversidade de espécies e fitofisionomias existentes. Esse tipo de estudo tem sido apontado como de grande relevância principalmente diante das situações atuais de desmatamento e mudanças climáticas, que exigem recuperação de áreas degradadas e prospectar como as espécies nativas sobreviveram diante deste ambiente de aceleradas mudanças. Nesta perspectiva, o objetivo deste trabalho foi investigar a dinâmica de crescimento de Tabebuia rosea, por meio do monitoramento mensal da fenologia apical e cambial caulinar e dos teores dos pigmentos fotossintetizantes: clorofilas a, b, totais e carotenoides. Os resultados obtidos foram correlacionados entre si e também com a sazonalidade das variáveis ambientais: temperatura, precipitação e fotoperíodo. No que se refere aos teores dos pigmentos fotossintetizantes, foi também avaliada as oscilações observadas nas folhas obtidas nas orientações geográficas: norte, sul, leste e oeste. O trabalho foi desenvolvido no Campus da Universidade do Estado do Rio de Janeiro, RJ, Brasil. A fenologia dos ápices caulinares foi acompanhada mensalmente a partir de observações qualitativas e quantitativas em 15 indivíduos. As amostras contendo a zona cambial foram obtidas por método não destrutivo e processadas segundo as técnicas usuais em histologia vegetal. A extração dos pigmentos fotossintéticos foi realizada em acetona 80%, com posterior centrifugação e análise ao espectrofotômetro em diferentes comprimentos de onda. Tabebuia rosea apresentou aumento na largura da zona cambial em número de camadas celulares e em micrômetros, diminuição do diâmetro radial da célula inicial fusiforme e aumento em micrômetros da camada de células em processo de alongamento e diferenciação do xilema secundário no mesmo período em que a copa das árvores estava ocupada por folhas adultas e com os teores mais elevados de clorofilas nas folhas, coincidindo com o período em que as variáveis ambientais apresentaram-se elevadas, corroborando os resultados já obtidos para outras espécies nativas da Mata Atlântica se desenvolvendo no estado do Rio de Janeiro. A maior concentração de carotenoides foi observada no período em que as variáveis ambientais apresentavam índices elevados e as plantas estavam mais expostas à radiação luminosa, possivelmente em função de um maior investimento em fotoproteção. Cabe destacar que o lado oeste da copa das árvores mostrou uma tendência em apresentar maiores concentrações dos pigmentos fotossintéticos estudados, resultado ainda não observado na literatura até o momento, o que pode ser uma estratégia da espécie em compensar níveis baixos de radiação solar com acúmulo de clorofilas.

Some physiological effects of two algal epiphytes on the surfgrass Phyllospadix torreyi Wats.

Measurement of the physiological effects of the red algal epiphytes Smithora naiadum (Anders.) Hollenberg and Melobesia mediocris (Fosl.) Setch. and Mason on Phyllospadix torreyi Wats. were made near Hopkins Marine Station, Pacific Grove, California. Field studies revealed a significant influence of these epiphytes on both the breakage incidence and length, with that of Melobesia being the most pronounced. Analysis of the photosynthetic rate of the seagrass shows a decrease in the photosynthetic maxima in both epiphytized samples at a light saturating intensity. Under light limiting conditions, an increase in photosynthetic efficiency and a change in chlorophyll a composition in both epiphytized sample types suggest an adaptive mechanism similiar to those found in terrestrial and aquatic shade plants.

小麦抗寒力诱导过程中特异性蛋白质的合成

以5个不同抗寒性小麦品种（不抗寒的春小麦京771，抗寒性中等的郑州741和济南13号，以及强抗寒性冬小麦农大139和燕大1817）为材料，对其在抗寒锻炼过程中所发生的可溶性蛋白及膜蛋白组分的变化进行了电泳图谱的分析。主要结果如下： 1、可溶性蛋白质电泳图谱的分析表明：人工低温锻炼20天后，在不同品种中新合成的多肽分子量分别为：郑州741是28，73 KD;济南13号是24，28和73 KD;农大139是28，60，65和68 KD;田间抗寒锻炼的燕大1817为15，28，51，60，65和68 KD。 2、不同抗寒性品种经人工低温锻炼20天后，新合成的膜多肽分别是：郑州741为30和68 KD;济南13号为30，58，68和81 KD;农大139为18，21，27，32和56 KD。田间锻炼的冬小麦燕大1817为21，29，36，43和83 KD。 3、脱锻炼后，抗寒特异性的多肽及与抗寒相关的膜多肽发生减少或完全消失。 4、春小麦在低温锻炼后，抗寒力不显著提高，不产生抗寒特异蛋白质。此外，膜多肽的变化也较少。 以上结果进一步揭示和证实，在小麦的抗寒锻炼过程中无论是可溶性蛋白还是膜蛋白均确实有抗寒特异性蛋白的新合成，并在各品种间表现出某些共同的特异性多肽，这些新合成的多肽与品种的抗寒性存在密切的关系，品种愈抗寒，特异多肽的种类愈多。这些结果进一步证明，植物抗寒性是由多基因控制的。

Contrasting seasonal patterns in dimethylsulfide, dimethylsulfoniopropionate, and chlorophyll a in a shallow North Carolina estuary and the Sargasso Sea

Time series measurements of dimethylsulfide (DMS), particulate dimethylsulfoniopropionate (DMSPp), chlorophyll a (chl a), algal pigments, major nutrients, and the potential activity of DMSP lyase enzymes were made over a 2 yr period (6 March 2003 to 28 March 2005) near the mouth of the shallow, tidally mixed Newport River estuary, North Carolina, USA. DMSPp had a mean of 43 ± 20 nM (range = 10.5 to 141 nM, n = 85) and DMS a mean of 2.7 ± 1.2 nM (range = 0.9 to 7.0 nM). The mean DMS in Gallants Channel was not significantly different from that measured in the Sargasso Sea near Bermuda during a previous 3 yr time series study (2.4 ± 1.5 nM), despite there being a 43-fold higher mean chl a concentration (4.9 ± 2.4 µg l–1) at the coastal site. In winter, DMS was low and chl a was high in the surface waters of the Sargasso Sea, while the opposite was true at the coastal site. Consequently, DMS concentrations per unit algal chl a were on average 170 times higher in the Sargasso Sea than at the coastal site during the summer, but only 7 times higher during the winter. The much higher chl a-specific DMS concentrations at the oceanic site during the summer were linked to higher ratios of intracellular DMSP substrate and DMSP lyase enzyme per unit chl a. These differences in turn appear to be linked to large differences in nutrient concentrations and solar UV stress at the 2 sites and to associated differences in the composition of algal assemblages and physiological acclimation of algal cells.

Scientific assessment of marine harmful algal blooms

Algae are the most abundant photosynthetic organisms in marine ecosystems and are essential components of marine food webs. Harmful algal bloom or “HAB” species are a small subset of algal species that negatively impact humans or the environment. HABs can pose health hazards for humans or animals through the production of toxins or bioactive compounds. They also can cause deterioration of water quality through the buildup of high biomass, which degrades aesthetic, ecological, and recreational values. Humans and animals can be exposed to marine algal toxins through their food, the water in which they swim, or sea spray. Symptoms from toxin exposure range from neurological impairment to gastrointestinal upset to respiratory irritation, in some cases resulting in severe illness and even death. HABs can also result in lost revenue for coastal economies dependent on seafood harvest or tourism, disruption of subsistence activities, loss of community identity tied to coastal resource use, and disruption of social and cultural practices. Although economic impact assessments to date have been limited in scope, it has been estimated that the economic effects of marine HABs in U.S. communities amount to at least $82 million per year including lost income for fisheries, lost recreational opportunities, decreased business in tourism industries, public health costs of illness, and expenses for monitoring and management. As reviewed in the report, Harmful Algal Research and Response: A Human Dimensions Strategy1, the sociocultural impacts of HABs may be significant, but remain mostly undocumented.

高产小麦旗叶和芒细胞结构及其光合性能的研究

小麦旗叶的光合产物是其籽粒碳水化合物的主要来源，因此如何提高旗叶的光合能力从而提高小麦产量一直是小麦研究的热点。但是以往对高产小麦旗叶的研究主要集中在光合功能和生理生化指标等方面，很少涉及其结构与功能的联系，以及对亲本与子代的旗叶进行对比观察。本文以冬小麦亲本小偃54 、8602及其子代小偃81（高产品种）灌浆期的旗叶为材料，应用细胞离析法、组织切片和荧光显微技术等，对旗叶中叶肉细胞形态、叶绿体数目、叶片厚度、维管束数目和面积等进行了比较观察和测定，旨在探讨小麦旗叶结构与其光合效率的关系。研究结果表明，与亲本小偃54、8602相比，子代小偃81的叶片较厚，横切面内中央大维管束的周长与面积较大;高环数叶肉细胞所占比例、叶肉细胞的周长及其平面面积和细胞内叶绿体的数目等均大于亲本。由此可见，通过小麦品种的改良确实能使其旗叶的结构与光合细胞发生了明显的变化，从而为植物细胞结构和功能的密切关系提供了有力的证据;同时也为作物改良育种提供了又一种新的育种目标。 　　小麦非叶器官之一的芒，对其结构与光合特性关系的研究尚不够深入和广泛。本实验以具芒小麦高产耐旱品种京411籽粒不同发育时期的芒及旗叶为材料，对其叶绿体结构、放氧速率和磷酸烯醇式丙酮酸羧化酶(PEPCase EC 4.1.1.31)的活性进行了比较观察和测定。超微结构显示，从抽穗期开始，芒和旗叶中的叶绿体基粒及其垛叠度均有增加，之后由灌浆末期开始，叶绿体的膜系统开始逐渐解体。通过放氧速率的测定表明，在芒和旗叶中，光合速率在前几个时期呈上升趋势，随着器官的衰老逐渐下降，但是，旗叶放氧速率的下降比芒中更早。另外，芒的PEPCase活性在籽粒发育的整个过程中均高于旗叶，其中以籽粒干物质形成末期尤为显著。因此，芒对高产小麦籽粒的形成，特别是在干物质形成的后期起着更为重要的作用。 　　

全球变化下中国东北样带植物多样性梯度分析及气候-NDVI-植被的关系研究

中国东北样带（NorthEast China Transect, NECT）是位于中纬度温带以降水量作为主要驱动因素的陆地样带。本文的工作以此作为研究平台，利用生态信息系统（Ecological Information System, EIS）以及Microsoft Excel 7.0软件包建立了样带的地理数据库和植物多样性数据库，包括气候数据库、植被数据库、遥感数据库和内蒙内C_4植物数据库以及样带内生态系统特征数据库。在此基础上，主要研究了以下四个方面的内容： 1. 利用Holdridge的生命地带方法对NECT内的生物群区进行了划分。 主要是确定了生物群区间过渡带的位置与宽度，并预测了在全球变化三种模式下NECT内生物群区，尤其是过渡带的变化图景。湿度升高2 ℃后，过渡带的面积都呈扩大化的趋势。森林区对于降水量的变化反应很敏感。荒漠灌丛（即荒漠草原类型）由于其水热条件处于样带内较极端类型，因而对于全球气候变化反应也比较敏感。 2. 研究了NECT内的α、β多样性以及包括生活型、水分生态型、区系地理成分等在内的植物群落特征多样性的梯度变化规律。 研究了样带内的多样性梯度，提出了在样带内存在的α多样性测度问题以及β多样性沿样带的变化规律：样带内由东到西，β多样性逐渐升高，群落内物种被替代的速率变慢;两种植被类型边界上的两个样地之间的相似程度由东到西呈上升趋势;同一类型群落之间的物种周转率比不同类型群落间的物种周转率相对要低。同时将各个环境因子与α、β多样性作了回归分析，找出样带内决定α、β多样性的主要环境因子指标。 样带内沿43.5°N一线附近植物群落的生活型共有17类，水分生态型8类，区系地理成分包括17类，以此为基础分析了群落特征沿样带的变化规律。并探讨了生活型分布的历史地理原因。 3. 对样带气候－NDVI间的关系以及植被－NDVI的关系进行了探讨。 利用来自气象卫星的遥感数据一归一化植被指数（NDVI），和数值化后的样带1:100万植被图进行叠加，找到NECT内每种植被类型对应的NDVI值。样带内共有植被类型147种，反映在NDVI变化上的植被类型有106类。其中，自然植被101种。 影响年均NDVI分布的因子主要有经度、辐射日照百分率及7月温度，与经度呈正相关，与辐射日照时数及7月温度呈负相关。回归方程如下： NDVI = -220.426 + 3.273Lon - 80.338Ratio - 1.962T_7 (R~2 = 0.9714, F = 521.52, p < 0.001) 4. 研究了NECT内的光合功能型。 主要包括内蒙古地区的C_4植物及其生态地理特性。揭标C_4植物的分类群特性、生活型、水分生态型与区系地理成分等生态学特性。C_4植物分布的科属极其集中。C_4光合型为维管植物某些分类群（科、属、种）的特性，为它们固有的遗传特性。推断C_4起源于草本的某些科属。C_4植物为喜热、耐旱的类群。世界种、泛热带种、泛地中海种C_4植物较集中。 样带内的C_3、C_4功能型及其与环境因子的相关性。样带内C_4和C_3光合型植物组成比例由东到西表现出两高两低的趋势。分布主要与年均温和降水量呈显著相关。 提出了一种新的C_3、C_4鉴别方法。即根据野外测定的光合数据建立了C_3、C_4的判别模型： f_1(x) = -1.5493 + 0.1427Pn + 0.1035Tr + 0.3768ΔT + 0.1000Gs f_2(x) = -15.6142 + 1.0542Pn - 0.2503Tr - 0.2957ΔT + 0.6491Gs 最后，综合7个GCMs模型（GFDL，GISS，LLNL，MPI，OSU，UKMOH，UKMOL）的输出结果，利用此结果和本文建立的回归模型，模拟了样带内生物多样性的窨分布格局，并预测了末来全球变化下归一化植被指数NDVI的空间分布格局的变化。

大豆（Glycine max (L) Merr.）生理生态特性及其与产量的关系

本论文由三部分组成: 1) 大豆高产品种黑农40与低产品种黑农37不同发育时期叶片光合生理生态特性的研究;以不同产量水平的东北大豆黑农40和对照品种黑农37为试验材料，研究了从幼苗期到衰老期五个不同发育时期叶片光合作用特性的变化。尤其是系统的研究了光合作用、蒸腾作用和水分利用效率的变化之间的联系，以及气孔导度和胞间CO2浓度的相随变化。发现净光合速率和产量之间存在明显的正相关关系，各个光合生理生态参数之间也有密切的关系。 2) 在大豆生长过程的重要时期结荚期，对大豆品种黑农37和黑农40的光合和水分特性的日变化研究;测定结荚期黑农37和黑农40的光合作用、蒸腾作用、气孔导度和水分特征(水分利用效率和水势)的日变化以及它们之间可能存在的联系，并分析了光抑制的现象,研究表明在晴朗的一天中，光合速率的日变化呈双峰曲线，在整个日变化中，黑农40的净光合速率都比黑农37的要高。黑农40和黑农37相比，在水分亏缺的情况下黑农40能维持较高的水势和水分利用效率，特别是在中午的时候，差别更加明显。 3) 比较研究了1970s 、1980s 和1990s 期间不同大豆 (Glycine max (L) Merr.)品种的生理生态特性：光合作用、蒸腾作用、水分利用效率和叶片水势，分析了各生理生态特性之间以及与产量的关系。研究表明光合速率和产量之间存在显著的相关关系，大豆叶片水势和净光合速率之间也存在明显正相关关系，高产大豆在水分亏缺的情况下仍能维持较高的的水分利用效率和水势。

异质性环境中两种匍匐茎草本植物的克隆可塑性

　　克隆植物常常生长在资源异质性分布的环境中，克隆植物特有的生活史特征使其对环境和资源变化产生的反应规范（Reaction norm）具有特殊的表现和适应意义。本文以匍匐茎草本植物蛇莓(Duchesnea indica)和活血丹(Glechoma longituba)为材料，研究克隆植物在不同异质性环境中的反应规范，即可塑性（plasticity）和克隆分株间相互作用（即克隆整合（clonal integration））对表型的影响及其适应意义。 蛇莓和活血丹是具有不同分枝类型的两种匍匐茎草本植物。对于匍匐茎草本植物而言，生境中光资源分布在时间和空间上的变化极为丰富。本文主要研究在不同环境中，这两种克隆植物克隆分株间的相互作用是如何通过影响其形态特征，从而影响其光资源获取策略。 实验涉及了4种光照条件，分为5个部分，分别在大棚和野外进行。 1．同质光环境中蛇莓和活血丹克隆片段的可塑性 在大棚中，将整个克隆片段（clonal fragment）都放置在光照强度分别为自然光照PPFD（Photosynthetic Photon Flux Density）的100％、50％和10％三种不同的同质光环境中，目标是通过比较不同光照强度同质环境中不同基因型的形态特征，揭示匍匐茎草本克隆植物的反应规范及遗传差异。实验结果发现，当光照强度从100% PPFD 降到 50% PPFD时，活血丹增加对地上部分生物量投资，增加部分多投入到匍匐茎上，用于支持匍匐茎实现觅食行为，叶片和叶柄的变化不大。同样条件下，蛇莓的生物量投资却向根部转移，地上部分叶片和叶柄形态上的变化比匍匐茎的形态变化显著，出现增强对光资源吸收能力的变化。当光照强度从50%降到 10%时，活血丹继续增加对地上部分的生物量投资，但由于光照强度弱，几乎不足以维持新的匍匐茎的发生，所有增加的生物量部分都投入到叶片和叶柄的变化上。这种条件下，蛇莓的生物量投资依然向根部转移，叶片和叶柄为增加对光资源吸收能力而发生了相应变化，匍匐茎的新增数减少，形态变化也不大。实验证明，可能由于匍匐茎的发生方式不同，活血丹的匍匐茎节间长度，叶片和叶柄的关联程度比蛇莓相应性状的关联程度强。不同基因型的蛇莓和活血丹对光照梯度的反应有显著差异。 2．异质光环境中蛇莓克隆片段的可塑性 针对克隆植物分株间在相当长的时间里形体相连，而环境异质性可能存在于分株大小的空间尺度，设置异质环境，将蛇莓的不同相连分株放置在不同的光资源斑块中，研究其整合作用在适应异质性环境过程中的作用及其对表型的影响。首先设置同一种资源（光资源）的梯度差异斑块。 在光斑块中，整合作用发生与否、作用方式与资源梯度、分株自身所处斑块的资源条件和分株的年龄结构有关。在不同的条件下，整合作用可能造成对表型的不同影响，从而可能加剧或削弱分株对本地资源的反应（局部反应，local response）。整合作用对分株局部反应的影响强度和方向，在不同基因型间存在明显差异。这些基因型间的差异暗示，整合作用可能也是具有遗传基础的一种独立性状。 3．光块斑和养分斑块共存环境中活血丹克隆片段的可塑性 设置光和养分的资源互补性斑块。将相连分株种植在不同斑块中。当生长在高光低养斑块中的分株与其互补斑块（低光高养斑块）的分株相连时，其适合度相关性状的值增加，根冠比是可塑的，通过相应的形态变化，高光照斑块中的分株捕获光资源的能力增强，但两种斑块中植株的吸收养分的能力却没有大的变化。收益－损耗分析显示整合作用有益于异质环境中的植株，低光高养斑块中植株的生物量获益。实验结果证明了异质环境中相连分株间存在光合产物和养分传递。在这种环境种，分株形态的变化对本地斑块发生趋富反应，形态的改变有助于对本地丰富资源的吸收。这种反应有利于克隆片段对资源的吸收。 4．野外环境中蛇莓克隆片段的可塑性 基于大棚实验资料，对野外林下蛇莓种群进行监测。首先对单株在林下复杂的光环境中的表现进行了跟踪，结果发现，随着分株数目的增加，适合度相关性状值有所提高，而处于不同位置的相连分株在形态上的差异不显著。大棚实验中发现的显著形态变化在具有显著差异的自然环境条件下没有发生，这可能暗示着在资源条件变化频率较高的环境中整合作用的作用方式。分株不是对某一时刻资源条件进行形态特化，而是通过对所扩展的总体区域的总的环境条件调整表型。这样，从克隆片段的水平上看，资源的吸收可能达到较高水平。在密度增大，植株间互相荫蔽使得光照减弱的情况下，匍匐茎的变化没有表现出觅食行为，叶片和叶柄出现增大增长等增强吸收光能力的相应表型变化，证明叶片叶柄是克服光照不足的主要器官。这些结果与大棚实验结果一致。蛇莓基株对于相连分株内部可能具有密度调节功能，从而通过减弱叶片增大的趋势，增长匍匐茎，分散新生分株，使密度保持在一定程度，不对种群的发展造成阻碍作用。非相连分株间随着密度的增大，相互间的作用方式类似于非克隆植物：出现叶片增大，叶柄增长的现象，同时密度制约了适合度相关性状如分株数目等的增加。 5．野外环境中蛇莓种群格局动态 最后，在进化的单位，种群水平上对蛇莓种群在自然界的动态进行了调查。Spearman相关分析，没有发现光资源和测量指标在量上的相关。在自然界中整合作用使大量分散分布、相互连接的分株相互作用，以促进基株对资源的获取。Moran’s I指数分析显示，随时间的推进，各个指标在相关尺度上有所增加。这暗示了整合作用的存在，分株间联系的加强。大棚实验中观察到的关于各个器官的作用的结论在自然界中得到进一步的验证。蛇莓匍匐茎在遮荫环境中不是作为觅食器官。为了争取对更多光资源的吸收，蛇莓在叶片数和叶形态上发生改变。对分株数、叶片数、匍匐茎数目的分布格局的调查显示出没有一定的规律性，而且处于不断的变化中。这一结果可能暗示种群发展过程中处理异质性分布资源的对策的变化。 此外，本文还揭示了可塑性和整合作用在基因型间的差异，针对所发现的现象，从作用的遗传机制上对可塑性及其适应意义进行了讨论。结合分子生物学和地统计学等学科的研究成果，对进一步的实验提出了方法和路线。

CO2浓度升高对羊草草原生产力和碳平衡的影响

自工业革命以来，大气的C02浓度以前所未有的速度增加，已经由280μmol mol-1升高到了360μmol mol-l。据预测，到下个世纪中／末期，C02浓度将为目前的二倍。C02浓度升高及其引起的全球气候变化必将影响到植物的生长发育，进而对整个生态系统产生巨大影响。因此，有关C02浓度升高对各类生态系统的影响的研究引起了广泛关注，成为近年来的研究热点。早期的研究多数集中于考察C02浓度升高对植物个体水平生长发育的影响。然而，高C02对植物的效应严重依赖于具体物种和具体环境条件，使得基于由短期盆栽实验获得的研究结果不能够有效地预测自然生态系统的行为。因此，长期、原位处理实验越来越受到重视。由于原位研究的难度较大，目前这方面的研究还不是很多。有限研究结果显示，由于生境条件和种间关系方面的巨大差异，自然生态系统对C02浓度升高的反应迥异。 草原生态系统由于C02浓度控制上比较容易实现，而且其物质循环相对较快，因而一直是C02富集实验研究最多的一类植被，生态系统水平的研究更是如此。然而涉及的区域和草原类型并不多，不足以进行可靠预测。目前，关于C02升高效应，研究比较系统的草原生态系统主要集中在：美国Kansas的高草草原、美国California的一年生草原、瑞士西北部的石灰质草原、美国Colorado的矮草草原和一些牧场。我国总土地面积的40%为草地，类型丰富，然而相关研究不多，尤其是对自然生态系统的原位研究几乎为空白。 为揭示C02浓度升高对羊草草原生产力和碳平衡的效应，我们在中国科学院内蒙古草原生态系统定位研究站的永久羊草样地开展了两年的C02倍增实验(2001，2002)。在羊草样地选择相对均匀地段设置12个开顶式气室（直径1.8m），每个气室内分成4个小样方(0.5m×0.5m)，其中6个气室在生长季给予加倍C02处理（约600μmol mol-l），另6个气室不补充C02（约300μmol moI-l）。地上部分用收割法取样，分种记录数量、高度和重量等指标，地下部分取样用环刀法。用Li-cor6400光合系统测定群落光合和呼吸速率。野外实验结束后，统一分析植物和土壤样品中的C、N等元素含量。另外，在内蒙古草原站院内设置了两组桶培实验，一组是取自羊草样地的带苗原状土，一组是取自羊草样地的混匀土，种上冰草(Agropyron cristatum)、紫花苜蓿(Medicago sativa)和无芒雀麦(Bromus inermis)的种子。2组桶培实验分别用两个水分梯度和两个C02梯度处理。水分处理分别为：浇水处理——每4天浇lOOOml水，相当于平均降雨量的160%;干旱处理——持续干旱，适时补水以保持植物不萎蔫，共浇水4000ml水。C02处理和取样方法与样地原位实验相同。主要研究结果和结论如下： 1)两年的C02加倍处理没有使羊草草原的生物量、植物种和功能型组成发生显著改变，桶培实验中，浇水处理显著促进了植物生长，原状土植物、种子苗实验的冰草和无芒雀麦对C02加倍处理同样不敏感，而种子苗实验的豆科植物紫花苜蓿在C02加倍处理下生物量显著提高。以上结果显示，由于水分和养分（特别是N）的限制，以及优势植物对C02的相对不敏感，C02浓度升高对羊草草原地上生物量和结构的效应相对不大。 2)羊草草原的根垂直分布在加倍C02条件下发生显著改变，但根生物量对C02加倍处 理相对不敏感。在4次取样中只有一次对C02加倍处理表现出显著变化，根长的变化与根生物量的变化不完全一致，根的比根长在加倍C02条件下增加。根垂直分布的变化趋势与降雨的时间分布相适应，干旱少雨时期C02使下层根量增加，多雨时期C02则使上层根量增加。以上结果显示，根的空间分布比根生物量对C02加倍处理更敏感。水分是根空间分布变化的驱动因子，加倍C02条件下，根空间分布的变化趋势倾向于优化对水分的充分利用。 3)加倍C02处理使羊草草原的群落光合速率显著提高，群落呼吸速率显著降低，因而使群落碳净输入量增加。土壤碳贮量占羊草草原碳总贮量的70%以上，碳总贮量及其组分（包括地上碳贮量、根碳贮量、土壤碳贮量）在两个C02浓度处理之问均没有显著差异。另外，加倍C02处理使羊草草原群落及其优势植物羊草的c：N比增加。以上结果显示，在加倍C02条件下羊草草原的碳净输入量增加，这意味着在未来高 C02条件F，羊草草原将作为碳汇对大气C02起反馈调节作用。其碳贮量对加倍C02 处理的不敏感与许多以前的研究结果相似，一般认为是由于土壤碳贮量本底太大， 掩盖了C02效应，这还有待于更长期原位实验的证实。羊草草原群落c：N比在高C02 浓度下的变化将影响凋落物降解、N素循环和动植物营养关系等，进而对生态系统 功能产生深远影响。

浑善达克沙地优势豆科植物 光合生理特性研究

　　氮素是植物光合生产的决定性因素，尤其是在沙地草地生态系统中，氮素贫乏往往限制植物的生长发育。因此，研究沙地植物光合作用与叶片N含量之间的关系，以及不同植物功能型氮素利用效率，有助于理解不同植物资源利用效率的差异。以浑善达克沙地分布的80种植物为研究对象，对不同生境(固定沙丘、丘间低地和湿地)、不同生活型(乔、灌、草)、不同光合途径(C3和C4)以及豆科和非豆科植物等功能型进行研究，结果表明：无论在单位叶面积水平还是单位干重水平上的叶片氮含量，均与光合速率成极显著正相关，但单位氮素的光合利用效率在不同生境以及不同功能型之间差异很大;光合氮素利用效率表现为：湿地植物>沙丘>丘间低地植物;草本植物>灌木>乔木;C4草本>C3草本植物，非豆科植物>豆科植物。 　　为了验证浑善达克沙地豆科植物是否比非豆科植物具有更高的光合潜力，我们比较研究了3种优势豆科植物小叶锦鸡儿(Caragana microphylla)、木岩黄芪(Hedysarum fruticosum var. lignosum)、披针叶黄华(Thermopsis lanceolata)和2种非豆科植物羊草(Leymus chinensis)和黄柳(Salix gordejeviii)，结果表明并非所有豆科植物都比非豆科植物有着显著高的光合速率，仅木岩黄芪表现出较高的光合速率，其它两种豆科植物的光合速率和羊草、黄柳的差异并不显著(P>0.05)，甚至低于后者，这是因为氮素利用效率(PNUE)在其中起关键作用，通过对影响PNUE的几个主要因素进行分析得出：叶绿素对光能的吸收、光化学转换效率和CO2分压并不是构成豆科和非豆科植物PNUE差异的主要因素，而Rubisco羧化效率决定了所实验的5种植物对氮素利用效率的高低。 　　木岩黄芪在浑善达克沙地的沙丘上为优势种，甚至成为流动沙丘的先锋种。除了其显著高的氮含量外，对沙丘胁迫生境的光合适应性是我们关注的另一个重点。通过对木岩黄芪和其伴生种黄柳的光反应曲线以及光合日动态的研究，发现木岩黄芪具有显著高的光合速率、水分利用效率和PSII 光化学效率，其忍受中午强光和高温的能力较强(即“光合午休”现象不明显)。另外，该物种还表现出了显著高的光饱和点和低光补偿点。 对木岩黄芪的模拟降雨试验结果表明：气体交换参数以及叶绿素荧光参数均受到干旱和模拟降雨的影响，其中气孔因素和非气孔因素共同决定了干旱条件下木岩黄芪光合速率的降低;但降雨解除干旱后，气孔导度恢复较快，而PSII 潜在活性和PSII 光能转换效率的恢复却比较缓慢。在0-15mm的降雨量范围内，随降雨量的增加各项生理指标不断升高，但大于15mm的降雨量对木岩黄芪影响不大，因此木岩黄芪可被视为低耗水型植物。 　　对木岩黄芪光合酶的研究结果表明，其C4光合酶的活性很高，磷酸稀醇式丙酮酸羧化酶(PEPcase)、NAD-苹果酸酶(NAD-ME)、NADP-苹果酸酶(NADP-ME)、NAD-苹果酸脱氢酶(NAD-MDH)、NADP-苹果酸脱氢酶(NADP-MDH) 和丙酮酸磷酸双激酶(PPDK)等酶的活性，在整个生育期内为黄柳的5倍以上，但稳定性碳同位素测定结果却表明木岩黄芪为C3植物。因此，我们认为C3豆科植物木岩黄芪体内可能存在着C4光合途径，这种机制使得其对于流动沙丘的胁迫环境有着很强的适应性和很高的资源利用效率。