Revisits to emptied cache sites by Clark's nutcrackers (Nucifraga columbiana)

During cache recovery experiments, Clark's nutcrackers (Nucifraga columbiana) often revisit cache sites that were emptied during previous recovery sessions (Kamil & Balda 1985). In the current experiments, nutcrackers were allowed to cache pine seeds and recover them in several recovery sessions. The results of two experiments demonstrate that neither leaving signs of previous digging activity nor leaving many pine seeds in the caches affects the tendency to revisit.     

Comparison of survey methods for monitoring Clark's Nutcrackers and predicting dispersal of whitebark pine seeds

ABSTRACT Clark's Nutcrackers (Nucifraga columbiana) disperse seeds of whitebark pines (Pinus albicaulis) in western North America by their scatter‐hoarding behavior. Because of declines in whitebark pine, resource managers are seeking an effective means of monitoring nutcracker population trends and the probability of seed dispersal by nutcrackers. We tested the reliability of four survey techniques (standard point counts, playback point counts, line transects, and Breeding Bird Survey routes) for estimating population size by conducting surveys at sites where a portion of the nutcracker population was marked with radio transmitters. The efficacy of distance sampling, based on detection rates from our unadjusted surveys, was also assessed. We conducted counts of whitebark pine cones within stands and related the probability of seed dispersal within stands to cone production and nutcracker abundance. We conducted 70 h of surveys for Clark's Nutcrackers at eight sites from July through November in 2007 and 2009 and estimated cone densities at six of these sites. Detection rates for all survey techniques were low and variable and we detected an average of 5.6 nutcrackers per 30 min of survey time. We also found no difference in detection rates among survey types, although significantly more nutcrackers were detected during surveys conducted during the peak of whitebark pine cone harvest (P < 0.0001). Nutcracker abundance was not correlated with cone density (P= 0.29) and we observed nutcrackers pouching seeds at all sites. Thus, cone density did not provide reliable information on whether seed dispersal was likely to occur. We suggest that alternate methods be considered for monitoring populations and assessing seed dispersal probability because we did not reliably detect nutcrackers using conventional survey techniques and because nutcracker abundance was not correlated with cone density.     

Discrimination among pinyon pine trees by Clark's Nutcrackers: effects of cone crop size and cone characters

Summary The influences of Colorado pinyon pine (Pinus edulis) cone crop size, cone and seed weight, cone length, number of seeds per cone, number of viable seeds, and percent viable seeds on the foraging behavior of avian seed dispersal agents were examined in field and laboratory settings. In the field, there was a significant positive relationship between cone number per tree and both the absolute number of cones and the percentage of the cone crop from which seeds were harvested. Cone weight and the number of viable seeds were also significantly related to seed harvest intensity. Laboratory experiments examined the relationship between crop size and cone characters on seed harvest by 18 Clark's Nutcrackers (Nucifraga columbiana). Nutcrackers were offered a choice of two tree types: one with 20 cones attached, and another with 10 cones attached. Significantly more birds chose to remove seeds first from the tree with 20 cones than the tree with 10 cones. In timed trials, they also harvested seeds from significantly more cones on the tree with the higher cone density. In the laboratory, cones chosen for seed removal by the nutcrackers had significantly more viable seeds, more seeds, and were longer compared to cones that were not chosen. Such discriminatory foraging behavior may increase avian foraging efficiency and result in differential reproductive success of pinyon pines. This behavior may therefore influence the evolution of pinyon pine reproductive traits.     

种子的脱水行为及其分子机制

成熟脱水是种子发育的末端事件。根据种子的脱水行为,可以把种子分为正常性、顽拗性和中间性种子。许多过程或者机制授予或者提高种子的脱水耐性,不同的过程可能在不同的水合水平上对水分丧失起保护作用,这些过程的缺乏或者无效表达可能决定个别物种的种子的脱水敏感性程度。到目前为止,涉及种子脱水耐性的过程或者机制有：细胞内脱分化;代谢的‘关闭’;抗氧化系统的存在和有效运转;保护性分子(包括胚胎发育后期高丰度表达蛋白,蔗糖、寡糖或者半乳糖苷环多醇,亲水脂分子,油素)的存在;以及在重新水合过程中修复机制的存在和运转。     

Predicting the Size of Silver Nanoparticles from Their Optical Properties

Plasmonics - In this study, localized surface plasmon resonance (LSPR) of the spherical silver nanoparticles (AgNPs) was evaluated based on experimental and theoretical viewpoints. In the...     

Macrophages Recognize Size and Shape of Their Targets

Recognition by macrophages is a key process in generating immune response against invading pathogens. Previous studies have focused on recognition of pathogens through surface receptors present on the macrophage''s surface. Here, using polymeric particles of different geometries that represent the size and shape range of a variety of bacteria, the importance of target geometry in recognition was investigated. The studies reported here reveal that attachment of particles of different geometries to macrophages exhibits a strong dependence on size and shape. For all sizes and shapes studied, particles possessing the longest dimension in the range of 2–3 µm exhibited highest attachment. This also happens to be the size range of most commonly found bacteria in nature. The surface features of macrophages, in particular the membrane ruffles, might play an important role in this geometry-based target recognition by macrophages. These findings have significant implications in understanding the pathogenicity of bacteria and in designing drug delivery carriers.     

鸦胆子化学成分及肿瘤细胞毒活性研究(英文)

从鸦胆子(Brucea javanica)种子的甲醇提取物中分离和鉴别得到11个化合物,经波谱数据分析分别鉴定为鸦胆子内酯A(1),鸦胆子素D(2),鸦胆子苷A(3),C(4),F(5),G(6),L(7),3β-羟基-孕甾-5-烯-20-酮(8),3β-羟基-5α-孕甾-20-酮(9),3-O-β-D-吡喃葡萄糖基-(1→2)-α-L-吡喃阿拉伯糖基-(20R)-孕甾-5-烯-3β,20-二醇(10)和6,22-二烯-3β-羟基5,8-过氧麦角甾(11)。其中化合物8、9和11为首次从该植物中分离得到。鸦胆子内酯A(1)和鸦胆子素D(2)对人类癌细胞株BGC-823,Huh-7,KE-97和Jurkat具有很好的细胞毒作用。     

New Cardenolide Glycosides from the Seeds of Digitalis purpurea and Their Cytotoxic Activity

A chemical investigation of Digitalis purpurea seeds led to the isolation of three new cardenolide glycosides (1, 8 and 11), together with 12 known cardenolide glycosides (2–7, 9, 10 and 12–15). The structures of 1, 8 and 11 were determined by 1D and 2D NMR spectroscopic analyses and the results of an acid or enzymatic hydrolysis. The cytotoxic activity of the isolated compounds (1–15) against HL-60 leukemia cells was examined. Compounds 2, 9, 11 and 12 showed potent cytotoxicity against HL-60 cells with respective 50% inhibition concentration (IC₅₀) values of 0.060, 0.069, 0.038, and 0.034 µM. Compounds 2, 9 and 11 also exhibited potent cytotoxic activity against HepG2 human liver cancer cells with respective IC₅₀ values of 0.38, 0.79, and 0.71 µM. An investigation of the structure-activity relationship showed that the cytotoxic activity was reduced by the introduction of a hydroxy group at C-16 of the digitoxigenin aglycone, methylation of the C-3' hydroxy group at the fucopyranosyl moiety, and acetylation of the C-3' hydroxy group at the digitoxopyranoyl moiety.     

Size of Dominant Diatom Species Can Alter Their Evenness

Traditionally, biodiversity has often been estimated on the basis of abundance partly due to the need for complicated measurements of biomass. Here, we conducted robust measurements of the community composition and of the size structure of diatoms in the North Pacific to evaluate the importance of biomass on the biodiversity. We found that the two most useful evenness indices increased in most cases where small species were numerically dominant when calculations were based on biomass compared with those on abundance. Size-abundance spectra of diatoms revealed that numerically dominant small species rarely dominated in terms of biomass. On the other hand, intermediate to large diatom species generally played a dominant role in terms of biomass in diatom community. The results suggest that the size of the dominant species is a crucial factor in determining the role of diatoms in the ecosystem functioning. Because such size variability can also be observed in other organisms, we need to pay attention to the effect of size structures on biodiversity.     

滇南红厚壳种子的脱水敏感性及其影响萌发的因子

滇南红厚壳(Colophyllum polyanthum Wall.ex Choisy)种子的千粒重约为4700g,脱落时种子的含水量为45％(鲜重),其存活率对脱水高度敏感;当种子含水量降至30％以下时,存活率迅速下降;种子存活率的半致死含水量约为23％;可以认为它是一种典型的顽拗性种子。含水量为45％的种子,在20--30℃的范围内,随着温度的升高种子萌发50％所需要的时间缩短;高于和低于这个温度范围(如15℃,30℃),种子的萌发率均下降;变温处理有利于提高种子的萌发率和萌发速率。除去种皮和切除部分子叶能提高种子的萌发率、萌发速率,以及种子萌发后的早期幼苗生长量。光照明显地促进整粒种子的萌发,但对除去种皮的种子、具有1／2子叶的种子、以及胚轴的萌发没有影响。     

一种提取高质量油菜种子和种皮RNA的方法

提取高质量的RNA是从基因表达水平上研究油菜种子和种皮发育的必要条件。现有方法因为油菜种子脂肪、多酚和多糖,难以快速获得完整、高纯度的油菜种子总RNA。本试验针对油菜种子和种皮特点,利用苯酚-氯仿抽提后用无水乙醇沉淀RNA,建立了在油菜种子和种皮中快速提取高质量总RNA的提取方法,电泳分析表明28S rRNA亮度约为18S rRNA的2倍;紫外分光光度计检测A260/A280介于1.8～2.0之间。用该法分离的RNA,已成功用于RT-PCR、Northern blot分析和基因全长的克隆等分子生物学研究。     

Effects of resource availability and distribution on autumn movements of the Nutcracker Nucifraga caryocatactes in the Alps

Radiotracking was used to study the ranging behaviour and movements of the Nutcracker Nucifraga caryocatactes in the Alevé forest (northwest Italian Alps), from September to December 1994-96, when Nutcrackers collected seeds of Arolla Pines Pinus cembra. Home range size and overlap decreased from September to December. Autumn ranging behaviour was not consistent with territoriality. Nutcrackers stored seeds throughout the Alevé; many apparently stored seeds in scree at high altitudes (above 2200 m) where the forest comes to an end, and also in Larch forests opposite the Alevé (probably to avoid competition with rodents and conspecifics). Estimates of Nutcracker abundance, derived from transect counts, varied significantly among habitats, years and months, which possibly reflected differences in seed availability and abundance. The ranging behaviour observed at the Alevé was compared with that monitored at Mont Avic, another area in the northwest Italian Alps, where resources (in this case Hazel Corylus avellana nuts) were concentrated in a few zones. Home range size was significantly larger at Mont Avic, especially during late autumn. There, the home range size increased and overlap decreased from September to November, when birds abandoned Hazels and dispersed to the coniferous woods. Differences between Alevé and Mont Avic implied that the availability and distribution of resources are the major determinants of the ranging behaviour of the Nutcracker during autumn. However, differences between adults and juveniles were also found.     

Flavonoids from Seeds of Camellia semiserrata Chi. and Their Estrogenic Activity

Two new flavonol glycosides and three known flavonoids were isolated from seeds of Camellia semiserrata Chi. The structures of these new flavonol glycosides were established as kaempferol 3-O-[(2'''',3'''',4''''-triacetyl)-α-L-rhamnopyranosyl(1→3)(2''',4'''-diacetyl)-α-L-rhamnopyranosyl (1→6)-β-D-glucopyranoside] and kaempferol 3-O-[(3'''',4''''-diacetyl)-α-L-rhamnopyranosyl(1→3)(2''',4'''-diacetyl)-α-L-rhamnopyranosyl(1→6)-β-D-glucopyranoside] by spectroscopic methods. The estrogenic activity of these compounds was investigated by a recombinant yeast screening assay.     

Reduced Germination of Orobanche cumana Seeds in the Presence of Arbuscular Mycorrhizal Fungi or Their Exudates

Broomrapes (Orobanche and Phelipanche spp) are parasitic plants responsible for important crop losses, and efficient procedures to control these pests are scarce. Biological control is one of the possible strategies to tackle these pests. Arbuscular Mycorrhizal (AM) fungi are widespread soil microorganisms that live symbiotically with the roots of most plant species, and they have already been tested on sorghum for their ability to reduce infestation by witchweeds, another kind of parasitic plants. In this work AM fungi were evaluated as potential biocontrol agents against Orobanche cumana, a broomrape species that specifically attacks sunflower. When inoculated simultaneously with O. cumana seeds, AM fungi could offer a moderate level of protection against the broomrape. Interestingly, this protection did not only rely on a reduced production of parasitic seed germination stimulants, as was proposed in previous studies. Rather, mycorrhizal root exudates had a negative impact on the germination of O. cumana induced by germination stimulants. A similar effect could be obtained with AM spore exudates, establishing the fungal origin of at least part of the active compounds. Together, our results demonstrate that AM fungi themselves can lead to a reduced rate of parasitic seed germination, in addition to possible effects mediated by the mycorrhizal plant. Combined with the other benefits of AM symbiosis, these effects make AM fungi an attractive option for biological control of O. cumana.     

The central role of Clark's nutcracker in the dispersal and establishment of whitebark pine

Summary Plant and soil water relationships in a typical nebraska Sandhills prairie were examined to 1) explain the observed distribution patterns of several dominant grasses along a topographic gradient, and 2) show how spatial and temporal variations in soil moisture are critical to community organization on a sandy substrate. An experimental transect encompassing the major community and soil types along a steep, west-facing vegetated dune was established. Maximum available water was shown to be significantly higher in the fine textured surface soils of the lowland sites than the coarse textured sands of the dune sites. Seasonal (1979) patterns of available soil moisture of the sampling sites on the transect showed that in the upper elevation dune sands, moisture was available in the entire profile with surface depletions not occurring until mid to late summer. In contrast, moisture in the surface 60–80 cm in the fine textured lowland soils was exhausted by early to mid-summer with the entire profile nearly dry by late summer. Deep-rooted, C₄ species, Andropogon hallii and Calamovilfa longifolia which are common on upper, coarser sandy soils showed significantly greater water stress on fine textured soils than on dune sands. C₃, shallowrooted species, Agropyron smithii, Stipa comata, and Koeleria cristata always experienced lower mid-day and predawn leaf water potentials than the C₄ species. The C₃ species, with the exception of Koeleria are most abundant on finer textured soils that provide substantial moisture during their peak activity in the spring. It appears that the C₄ species show more conservative water use patterns than the C₃ species as significantly lower leaf conductances in the C₄'s were measured when soil water was abundant. The C₃ species appear to be opportunistic with available water and rapidly deplete surface soil moisture as a result of high transpiration rates. These data suggest that the temporal and spatial distribution of available water along this gradient controls species distribution according to rooting morphology, photosynthetic physiology, and water deficits, incurred by transpirational losses. Competitive interactions between species that utilize soil moisture differently may be an important factor in community organization.     

葡萄属种子发育的物候、萌发行为及其对冷层积的反应

以3个起源和分布中心的不同葡萄种及其杂交种作为实验材料,观察了开花、果实和种子成熟的物候,研究了成熟种子的基本特性和最初萌发率以及冷层积对成熟种子萌发的影响。结果表明,葡萄种子具有休眠特性,生理成熟时都具有分化完全的胚,在休眠解除过程中胚的形态不发生变化;美洲种休眠最深,欧亚种休眠最浅,其它种类的葡萄种子的休眠程度介于美洲种和欧亚种之间;不同种葡萄花期、果实和种子成熟过程的物候存在差异,果实成熟与种子成熟不同步,其间隔时间越短,种子休眠程度越深。冷层积60天能有效地解除东亚种、欧亚种、欧山杂种和蘡欧杂种的种子休眠,但对解除美洲种、美洲种种间杂种和欧美杂种的种子休眠效果较差。