Effect of natural atmospheric CO2 fertilization suggested by open-grown white spruce in a dry environment

Evidence of an atmospheric CO₂‐fertilization effect on radial growth rates was uncovered for open‐grown white spruce in a mixed‐grass prairie of southwestern Manitoba, Canada. Consistent upward trends of the residuals from dendroclimatic models indicated a decreased ability for climatic parameters to predict radial growth. Despite that a similar amount (61%) of the total variation in radial growth index was explained by climate for both young and old trees, residuals from young trees for the period of 1955–1999 demonstrated a stronger upward trend (R²=0.551, P<0.0001) than old trees for the period of 1900–1996 (R²=0.020, P=0.167). Similar to young trees, the residuals from the early growth period (1900–1929) of old trees also demonstrated a stronger upward trend (R²=0.480, P<0.0001) than the period of 1900–1996. Likewise, a comparable period (1970–1999) of young trees also demonstrated a stronger upward trend (R²=0.619, P<0.0001) than the early growth period (1900–1929) of old trees. In addition, postdrought growth response was much stronger for young trees (1970–1999) compared with old trees at the same development stage (1900–1929) (P=0.011) or within the same time period (1970–1999) (P=0.014). There was no difference (P=0.221) in drought recovery between the early (1900–1929) period and the late (1970–1999) period within old trees. Together, our results suggest that (1) open‐grown white spruce trees improved their growth with time at the early developmental stage, and (2) at the same developmental stage, a greater growth response occurred in the late period when atmospheric CO₂ concentration, and the rate of atmospheric CO₂ increase were both relatively high. While it is impossible to rule out other factors, these results are consistent with expectations for CO₂‐fertilization effects.     

Electrochemical and kinetic response of heterobinuclear Ni(II)Zn(II) complexes derived from unsymmetrical lateral macrobicyclic tricompartmental ligands

Using the precursor compound 3,4:10,11-dibenzo-1,13[N,N′-bis{(3-formyl-2-hydroxy-5-methyl)benzyl}diaza]-5,9-dioxocyclopentadecane, a series of macrobicyclic heterobinuclear Ni(II)Zn(II) complexes have been synthesized from the corresponding mononuclear nickel(II) complexes via a template method by Schiff’s base condensation. Electrochemical and kinetic studies of the complexes have been carried out on the basis of macrocyclic ring size. Cyclic voltammetry and controlled electrolysis studies indicate that the nickel(II) metal ion in the heterobinuclear complexes undergo quasireversible one electron reduction and oxidation, whereas the zinc(II) metal ion does not undergo any reduction and oxidation. All the heterobinuclear Ni(II)Zn(II) complexes are ESR inactive and diamagnetic in nature. The kinetics of hydrolysis of 4-nitrophenyl phosphate explores that the catalytic activities of the complexes are found to increase with macrocyclic ring size of the complexes. As the macrocyclic ring size increases, the spectral, electrochemical and catalytic studies of the complexes show variation due to distortion in the geometry of metal centre.     

Incorporation of 5-aminolevulinic acid into chlorophyll in darkness in barley

The incorporation of radioactive aminolevulinic acid (ALA) into chlorophyll (Chl) a and b , as well as protochlorophyllide (Pchlide) in light-grown barley seedlings ( Hordeum vulgare L. cv. Clipper) transferred to darkness is demonstrated.
In the experiments described, 6-day-old, glasshouse-grown seedlings were transferred to darkness and incubated in [¹⁴C]- or [³H]- ALA for 18 h.
Chl a and b were extracted and purified to constant specific radioactivity by HPLC and TLC of their magnesium-free derivatives, pheophytin a and b . The presence of label in the tetrapyrrole ring of the Chls was established by removal of the phytol chain by alkaline hydrolysis and determination of the specific radioactivity of the chlorin e ₆ and rhodin g ₇ derivatives.
Barley seedlings that had been grown in darkness for 5 days, transferred to light for 20 h, and then returned to darkness in the presence of radioactive ALA also incorporated label into Chl. However, this was only apparent in intact seedlings. Excised leaves from greened etiolated plants did not incorporate ALA into Chl in darkness. This was consistent with the finding of Apel et al. (K. Apel, M. Motzkus and K. Dehesh, 1984. Planta 161: 550–554) and may account for their failure to obtain evidence for a light-independent protochlorophyllide reductase in greening barley.
Although the incorporation of ALA into Chl compared to Pchlide was slight (5%), the presence of label in the tetrapyrrole nucleus of Chl a and b is unequivocal evidence of a light-independent pathway of Chl biosynthesis in barley that has been exposed to light during development. Limited entry of exogenous labelled ALA into the precursor pools leading to the dark reduction of Pchlide is postulated.     

Association of Criconemella xenoplax and Fusarium spp. with Root Necrosis and Growth of Peach

Criconemella xenoplax, Fusarium solani, and F. oxysporum caused necrosis of Nemaguard peach feeder roots in greenhouse tests. Root necrosis was more extensive in the presence of either fungus than wtih C. xenoplax alone. Shoot growth and plant height were less for plants inoculated with F. oxysporum or F. solani than for plants inoculated with the fungi plus C. xenoplax. Neither synergistic nor additive effects on root necrosis or plant growth occurred between C. xenoplax and the fungal pathogens.     

Environmental drivers interactively affect individual tree growth across temperate European forests

Forecasting the growth of tree species to future environmental changes requires a better understanding of its determinants. Tree growth is known to respond to global‐change drivers such as climate change or atmospheric deposition, as well as to local land‐use drivers such as forest management. Yet, large geographical scale studies examining interactive growth responses to multiple global‐change drivers are relatively scarce and rarely consider management effects. Here, we assessed the interactive effects of three global‐change drivers (temperature, precipitation and nitrogen deposition) on individual tree growth of three study species (Quercus robur/petraea, Fagus sylvatica and Fraxinus excelsior). We sampled trees along spatial environmental gradients across Europe and accounted for the effects of management for Quercus. We collected increment cores from 267 trees distributed over 151 plots in 19 forest regions and characterized their neighbouring environment to take into account potentially confounding factors such as tree size, competition, soil conditions and elevation. We demonstrate that growth responds interactively to global‐change drivers, with species‐specific sensitivities to the combined factors. Simultaneously high levels of precipitation and deposition benefited Fraxinus, but negatively affected Quercus’ growth, highlighting species‐specific interactive tree growth responses to combined drivers. For Fagus, a stronger growth response to higher temperatures was found when precipitation was also higher, illustrating the potential negative effects of drought stress under warming for this species. Furthermore, we show that past forest management can modulate the effects of changing temperatures on Quercus’ growth; individuals in plots with a coppicing history showed stronger growth responses to higher temperatures. Overall, our findings highlight how tree growth can be interactively determined by global‐change drivers, and how these growth responses might be modulated by past forest management. By showing future growth changes for scenarios of environmental change, we stress the importance of considering multiple drivers, including past management and their interactions, when predicting tree growth.     

闽东南地区马尾松古树对气候变化和虫灾的生态弹性

马尾松是我国南方地区广泛分布的先锋造林树种。在全球变暖、气候干旱化和虫灾频发的趋势下,研究马尾松对环境干扰的生态弹性对森林管理有重要意义。本文对福建省仙游县百松村的马尾松古树进行树木年轮样品采集,建立区域首个马尾松树轮宽度标准年表(1865—2014年)。结果表明: 当年7—9月低相对湿度和5—9月极端高温是树木生长的主要限制因素。根据树轮极端窄年确定1869、1889、1986、1991和1993是极端事件年。时序叠加分析发现,极端事件发生前两年的持续低值加剧了极端事件的影响。干旱年份更容易引发虫灾。1889年是受虫灾影响最严重的年份,1986和1991年受到虫灾和干旱气候的双重影响,其余极端年主要受干旱气候的影响。树木对虫灾的抵抗力弱于对干旱事件的抵抗力;除1991年外,树木对虫灾的相对弹性力高于对干旱事件的相对弹性力。1889年的相对弹性力最高,1991年受到连续极端事件的影响,相对弹性力最低。2000年以来研究区干旱化趋势加强,马尾松古树遭受干旱和虫灾的干扰加强,部分树木死亡。     

High resolution radiocarbon spike confirms tree ring dating with low sample depth

Radiocarbon (¹⁴C) has been used to date carbon-rich objects in Earth science, archeology, and history since the 1940s. New methods, using spikes in ¹⁴C caused by solar proton events, can be used to annually date wood when crossdating is not possible, such as when sample size is low, samples are floating in time, or external disturbances lead to insecure dates. Here, we use a spike in radiocarbon during a solar energetic particle (SEP) event in 774/775 CE to confirm crossdating of a poorly-replicated King Billy pine (Athrotaxis selaginoides) chronology. Low sample depth between 1498 and 1523 CE (two trees) prevented confident dating of the early period of the chronology. Three core samples with strong correlation with the master chronology that likely included the 774/775 CE Miyake SEP event were identified for radiocarbon isotope analysis. We sectioned segments centered on the estimated 774/775 CE date and then isolated the holocellulose in each sample. Samples were sent to an accelerator mass spectrometry (AMS) for radiocarbon measurements. The AMS data confirmed the crossdating accuracy of the tree ring series and reinforces the applicability of this technique to anchor poorly dated tree ring series in time. In addition, we found sample processing with a microtome proved superior for holocellulose extractions and yielded more accurate ¹⁴C measurements. We recommend sampling with a microtome, processing at least three samples per year, and including sample masses greater than 100 ug C to confirm dating using radiocarbon spikes.     

不同抗性苹果品种应答轮纹病菌胁迫的差异蛋白质组分析

为鉴定不同抗性苹果(Malus domestica)品种响应轮纹病菌胁迫的抗性相关蛋白表达差异, 以抗病品种华月及易感品种金冠为试材, 采用高通量同位素标记定量(IBT)技术结合液相色谱-串联质谱(LC-MS)鉴定技术, 对病原菌处理前后抗、感病品种叶片的蛋白质组差异表达进行分析, 共鉴定出171个差异表达蛋白(DEPs)。GO富集及KEGG通路分析表明, 在细胞组分、分子功能和生物过程3类中共注释到686个GO条目, 其中52个DEPs注释于KEGG通路的18个显著差异途径(P<0.05)。亚细胞定位预测分析表明, 171个DEPs中有170个分别定位于8类细胞器。蛋白功能注释分析表明, 46个DEPs注释于7类抗性相关蛋白, 包括类甜蛋白、过氧化物酶、多酚氧化酶、过敏原蛋白、几丁质酶、内切葡聚糖酶以及主乳胶蛋白。此外, 还对抗性相关蛋白的表达特点及基因定量结果进行了分析。该研究结果可为进一步解析抗、感病苹果品种应答轮纹病菌胁迫的抗性机制提供参考。     

关于"一类多分子生化反应系统的极限环"一文的补充

本文用构造无穷大外境界线的方法应用Ｐｏｉｎｃａｒｅ－Ｂｅｎｄｉｘｓｏｎ环域定理解决了系统ｘ＝δ-ｘｙｎ;ｙ＝ｘｙｎ-ａｙ／（ｙ+ｂ）存在极限环的充要条件,从而与文[１]共同完整地解决了此系统的定性分析．     

Microtubule nucleation: The waltz between γ-tubulin ring complex and associated proteins

Microtubules are essential cytoskeletal elements assembled from αβ-tubulin dimers. In high eukaryotes, microtubule nucleation, the de novo assembly of a microtubule from its minus end, is initiated by the γ-tubulin ring complex (γ-TuRC). Despite many years of research, the structural and mechanistic principles of the microtubule nucleation machinery remained poorly understood. Only recently, cryoelectron microscopy studies uncovered the molecular organization and potential activation mechanisms of γ-TuRC. In vitro assays further deciphered the spatial and temporal cooperation between γ-TuRC and additional factors, for example, the augmin complex, the phase separation protein TPX2, and the microtubule polymerase XMAP215. These breakthroughs deepen our understanding of microtubule nucleation mechanisms and will link the assembly of individual microtubules to the organization of cellular microtubule networks.