Are Nectar Sugar Composition and Corolla Tube Length Related to the Diversity of Insects that Visit Asteraceae Flowers?

Abstract: In this work, we analysed interspecific variation in nectar sugar composition, corolla tube length, and the diversity of floral visitors of 35 Asteraceae species. The potential correlations between these variables could arise either as a result of selection to improve pollinator attractiveness or simply as a consequence of phylogenetic constraints. Samples of nectar and flowers, and data on floral visitors, were obtained from living plants in natural populations from Argentina. Asteraceae species showed a large variability in corolla tube length. Nectar of most species presented a larger proportion of hexoses than sucrose. All species were visited by numerous insects belonging to 2 different orders. Results showed that floral traits are not significantly correlated with the diversity of floral visitors. These characters seem to be linked to the phylogeny of the species. Early branching species (species phylogenetically close to the root of the Asteraceae tree) tend to have longer corollas, higher sucrose proportions and lesser diversity of floral visitors than late branching species. Considering that longer corolla tubes and higher nectar sucrose percentages may indicate some specialization in the pollination system, we suggest that there is an evolutionary tendency toward generalist pollination systems within the family.     

Inter-specific differences in photosynthetic carbon uptake, photosynthate partitioning and extracellular organic carbon release by deep-water characean algae

1. The effect of light intensity on photosynthesis and the fate of newly fixed organic carbon was compared for three characean algae collected at the same depth (10 m) but differing in their depth distributions. For each species we determined photosynthesis–irradiance (P–E) responses, the partitioning of newly fixed carbon into four intracellular pools (low molecular‐weight compounds, polysaccharides, lipids and proteins) and the extracellular organic carbon (EOC) release at a range of photon flux densities (PFD) 0–60 μmol m^–2 s^–1. 2. The P–E responses differed between the three species, with the light compensation point (E_c) and dark respiration rate highest in the shallowest species (Chara fibrosa), intermediate in the mid‐range species (C. globularis) and lowest in the deepest species (C. corallina). Photosynthetic efficiency (α) and photosynthesis: respiration ratios were lowest in C. fibrosa and highest in C. corallina. 3. In all three species, the low molecular weight pool was the principal photosynthetic product (>60% of fixed C) at 3 μmol m^–2 s^–1 PFD, but its proportional contribution decreased rapidly with increasing irradiance. Polysaccharide rose to become the major product (>35% of fixed C) at saturating PFD (35 μmol m^–2 s^–1). 4. Protein synthesis was saturated at 5 μmol m^–2 s^–1 in all species and was consistently a lower proportion of the fixed carbon in C. corallina than the other species. The fraction incorporated in the lipid pool increased slightly with irradiance but was always less than 10% of fixed C, while the proportion lost as EOC was unaffected by light, being significantly higher in C. fibrosa than the other species. 5. A kinetic experiment with C. fibrosa at 35 μmol m^–2 s^–1 PFD revealed a continued increase in net polysaccharide, protein and lipid synthesis during a 22.5‐h light period, whereas the net size of the low molecular weight pool remained constant. In a subsequent dark period, protein and lipid synthesis continued at the expense of the polysaccharide and low‐molecular‐weight pools. The EOC release rose to a constant low release in the light, then peaked slightly immediately after the dark–light transition before returning to the same rate as in the light. Extrapolating these data over 24 h suggests that the proportion of fixed carbon lost as EOC may be as high as 10% in this species. 6. The interspecific differences in carbon acquisition between the three species reflected their depth distributions, with the deeper species having more efficient photosynthetic metabolism, lower P:R ratios and less EOC release, although no apparent differences in internal partitioning of photosynthate.     

Interactive effects of seed availability,water depth,and phosphorus enrichment on cattail colonization in an Everglades wetland

The relative importance of seed availability, waterdepth, and soil phosphorus (P) concentrations oncattail (Typha domingensis pers.) earlyestablishment in an Everglades wetland area wasexamined using seed bank analysis and controlledexperiments. The experiments measured seed germinationand seedling growth in tanks with cattail seedaddition subjected to two P concentrations(un-enriched vs. enriched) and water depth (saturatedvs. flooded soils). A limited seed bank (223 ± 69m²) of cattail was found in the surface soil ofthe area studied. The germination of added seeds wasinhibited under flooded conditions, and only 0.6% ofthe germination was found. In contrast,under-saturated soil conditions, a maximum of 6% and15% germination was observed in P-un-enriched andP-enriched treatments, respectively. High mortality ofseedlings occurred regardless of P treatments followinga cold spell. However, P enrichment resulted inincreased seedling growth and asexual propagation.These results suggested the importance of theconcurrence of appropriate hydrologic regimes, Penrichment, and air temperature on the recruitment ofplant species.     

底墒与磷肥互作对春小麦产量形成的影响

研究了浇底墒水和施磷肥对春小麦产量形成的影响.实验设4个处理对照(CK);耕作层施磷(P);浇30 nm底墒水(W);施磷加浇30mm底墒水(PW).测定土壤含水量、根系生物量、地上生物量和测产等.结果表明,WP处理根重和中下层分配比例均较高.与W处理相比,WP处理利用底墒并没有增加,但水分利用效率和产量均增加.决定产量的主要因素是小麦早期小穗和小花形成的数量和质量.W和WP两个浇底墒水的处理,其土壤水分利用量平均为34.6 mm,略高于所浇的底墒水的量(30 mm).CK、P、W、WP等4个处理的籽粒产量分别为91 7.7,1191.1,2516.5,2734.1 kg/hrm2,水分利用效率分别为0.186,0.192,0.172,0.207 g/(mm.m2).     

A theoretical consideration on oxygen production rate in microalgal cultures

Because algal cells are so efficient at absorbing incoming light energy, providing more light energy to photobioreactors would simply decrease energy conversion efficiency. Furthermore, the algal biomass productivity in photobioreactor is always proportional to the total photosynthetic rate. In order to optimize the productivity of algal photobioreactors (PBRs), the oxygen production rate should be estimated. Based on a simple model of light penetration depth and algal photosynthesis, the oxygen production rate in high-density microalgal cultures could be calculated. The estimated values and profiles of oxygen production rate by this model were found to be in accordance with the experimental data. Optimal parameters for PBR operations were also calculated using the model.     

Characterization of Depth-Related Changes in Bacterial Communities Involved in Mineral Weathering Along a Mineral-Rich Soil Profile

In this study, we used denaturing gradient gel electrophoresis (DGGE) and culture-dependent methodology to characterize bacterial populations and mineral-dissolving bacteria in a mineral-rich soil profile. DGGE and sequencing revealed 13 known bacterial families and 7 unknown populations for the soil profile. Seventy-one isolates could solubilize feldspar. Weathering effectiveness and pattern of the isolates differed among the horizons. The 71 mineral-dissolving isolates were affiliated with 32 bacterial species within 14 genera, among which Bacillus, Burkholderia, and Arthrobacter were dominant. Distinct mineral-dissolving populations were observed between the surface and subsurface horizons. Notably, the deepest horizon showed maximum diversity of the mineral-dissolving bacteria. Furthermore, a significantly higher proportion of the high efficiency mineral-dissolving bacteria was observed in the deeper horizons than in the upper horizons. The results suggested that the soil profile harboured diverse mineral-dissolving populations and the dissolving potential and pattern and the community of the mineral-dissolving bacteria changed with depth.     

中国34个省级行政区三维生态足迹动态研究

当前中国正处于生态文明建设的关键时期,东西部环境资源不均衡的格局日益加剧,限制了区域社会经济的可持续发展。基于资源、社会经济统计数据,利用三维生态足迹模型对中国34个省级行政区进行动态研究,细化不同类型土地的均衡因子与产量因子,刻画2009—2016年人均生态足迹广度、生态足迹深度的时空特征,并探讨分析省域间的资本利用格局及其社会经济影响因素。主要结论如下：人均生态足迹广度在省域间差异较大,且生态足迹深度均已超过自然原长1.00;足迹广度在研究期间呈先降后升趋势,最高值为西藏的10.87—12.35 hm2/cap,最小值为澳门的0.02 hm2/cap;且资本流量占用率并不充足,广西与上海分别仅为47.68%—67.34%、66.31%—68.88%。香港、澳门、宁夏的足迹深度远高于中国均值,分别为19.24—26.02、8.60—10.88、4.60—7.46,最小值为西藏（1.64—1.79）,其中耕地、化石能源用地的生态赤字贡献率最高,而林地则为生态盈余状态。将各省自然资本利用格局聚类分为4类并通过ArcGIS进行空间分析。基于改进的三维生态足迹模型并系统性地应用于中国34个省域,本研究定量化各省的自然资本利用格局,可为中国区域间资源配置、政策制定提供基础数据支撑及环境决策参考。     

沙漠腹地天然绿洲胡杨和柽柳叶片δ13C值对不同地下水埋深的响应

干旱区植物的水分利用效率对植物的分布及水分利用状况具有重要意义。基于不同地下水埋深条件下沙漠腹地绿洲优势种胡杨和柽柳叶片δ¹³C值,分析了胡杨和柽柳的水分利用效率对不同地下水埋深的响应。结果表明: 随着地下水埋深由2.1 m增加到4.3 m,柽柳叶片的δ¹³C值先略有增加后处于较为稳定状态,柽柳采取较为稳定的水分利用效率适应干旱环境;胡杨叶片的δ¹³C值呈现先略有减小后增加的趋势,胡杨通过提高水分利用效率的策略适应干旱胁迫。同一地下水埋深条件下柽柳叶片的δ¹³C值高于胡杨叶片,表明柽柳的水分利用效率高于胡杨。     

基于GTWR模型的浙江省海岸带三维生态足迹动态变化及其影响因素

厘清海岸带自然资本存量消耗和自然资本流量占用情况及其影响因素,能有效缓解海岸带社会经济发展与自然资源、生态环境之间的矛盾,促进区域协调可持续发展。本研究基于二维和三维生态足迹评价模型,分析浙江省海岸带2006—2016年生态足迹时空变化特征,基于足迹深度和足迹广度探究了区域自然资本存量和资本流量占用情况,并利用时空地理加权模型分析其影响因素的时空异质性。结果表明: 研究期间,浙江省海岸带生态危机加深,人均生态赤字平均值为3.5 hm²·cap^-1,人均生态赤字上升了15.5%,其中,能源消耗账户对人均生态足迹的贡献率大于生物资源账户;各县区人均生态足迹呈增长趋势,且空间分异显著。浙江省海岸带以消耗自然资本存量为主,且对自然资本流量更新起到较大的抑制作用;2016年,自然资本存量的消耗量是资本流量占有量的14.87倍。城市规模和经济发展水平、人民收入水平对浙江省海岸带各县区生态足迹以正向促进作用为主,渔业生产对生态足迹为负向影响,并有向正向影响作用转换的趋势,3个影响因子的影响机制时空分异性显著。     

播种季节和种植方式对多年生苦荞主要农艺性状的影响

该研究选取六个多年生苦荞新品系,对春季、秋季直播与秋季再生其主要农艺性状进行调查。结果表明:(1)不同播种季节对多年生苦荞新品系主花序的花粉可育率、总结实率、有效结实率、植株株高、主茎粗、主茎分枝数、主茎节数、籽粒百粒重、单株粒数、单株产量的影响均达到显著或极显著水平;秋播主花序花粉可育率、总结实率、有效结实率、植株主茎分枝数、籽粒百粒重、单株粒数、单株产量均极显著高于春播;植株株高、主茎粗、主茎节数均极显著低于春播;主花序花朵大小、籽粒种子长宽比无显著差异。(2)不同种植方式对主花序花粉可育率、有效结实率、植株主茎节数及籽粒百粒重的影响达到显著或极显著水平;秋季再生主花序花粉可育率、籽粒单株粒数显著高于秋季直播;主花序有效结实率、植株主茎粗、主茎节数、籽粒百粒重显著低于秋季直播;主花序花朵大小、总结实率、植株株高、主茎分枝数、籽粒种子长宽比、单株产量无显著差异;相关分析表明,各生长季节下主花序有效结实率及单株粒数与单株产量的相关系数均最高。(3)所有参试品系中,1612-241秋季直播的单株产量显著高于其他品系; 1612-16、1612-33秋季再生单株产量较正季优势显著。该研究结果有助于筛选出适宜一季播种两季收获的优良品系,为今后多年生苦荞的选择育种提供线索基础。