NAGase activity in airborne biomass dust and relationship between NAGase concentrations and fungal spores

Inhalation of airborne fungal spores or fungalenzymes may cause adverse pulmonary healtheffects. The enzyme NAGase(N-acetyl--D-glucosaminidase) is achitinase presumed to be secreted by all fungi. In this study, NAGase activities andconcentrations of fungi are estimated inairborne biomass dust to acquire knowledgeabout the level of NAGase activity and therelationship between NAGase activity andconcentrations of airborne fungal spores.NAGase was sampled on both teflon andpolycarbonate filters, and polycarbonatefilters proved to be better for extraction ofNAGase than teflon filters. NAGase was foundin airborne dust at a biofuel plant and in dustgenerated from biomass. At a biofuel plant, themedian level of exposure to NAGase was 21 pmols^–1 m^–3. Significant correlationswere found between NAGase activities, totalnumber of fungal spores and CFU of fungi, withthe highest degree of correlation being betweenthe total number of fungal spores and theNAGase activity (r = 0.802, n = 76). Furthermore,when dust was stored for different periods, theculturability of fungal spores was stronglyreduced and the NAGase activity was not or onlyslightly reduced after up to 40 days ofstorage. Accordingly, NAGase activity may beused as a rapid method to get an estimate ofthe exposure level to airborne fungal spores.Whether pure NAGase or the NAGaseconcentrations observed here cause any healtheffects is not known, although it has beenshown that other fungal enzymes can causerespiratory disorders and a chitinase isdescribed as an allergen.     

Fine root growth and element concentrations of Norway spruce as affected by wood ash and liquid fertilisation

A field experiment to test various management practices of sustainable forestry was conducted in a Swiss spruce forest for two growing seasons. Treatments were a control (C), yearly application of 4000 kg ha^–1 wood ash (A), daily irrigation with a steady state fertilisation as `optimal nutrition` (F) and irrigation with a water control (W). Samples were taken on a 5 × 5 m grid once a year with a soil corer to determine fine root biomass ( 2 mm) and soil pH of the topsoil. A subset of the fine root samples was further analysed for its nutrient composition by CN and ICP-AES analyses. The dynamics of root growth were observed with the aid of ingrowth-cores after 1, 1.5, and 2 years of treatment and the growth pattern was analysed in terms of biomass, tips, forks, length and root diameter of the samples. The A, F and also the W treatment resulted in a significant increase of soil pH in the topsoil. The fine root density increased over the two growing seasons, irrespective of the treatment. The root growth was only slightly different between the treatments with a initially faster growth under the A treatment. The W treatment reduced the number of root tips and forks, and the root length, while the A treatment increased the number of root tips, forks and the root length, but reduced the diameter. The differences between the three harvesting times (March 1999, October 1999, March 2000) of the ingrowth-cores stressed seasonal differences in root growth and the development of quasi `steady state' root dynamics. The root turnover was not changed by the treatments. The elements in the fine roots were strongly affected by the treatments A and F and sometimes by W. Fine root N increased with the F treatment, while C concentrations decreased under the A, F and W treatments. The Ca and Mg concentrations were strongly enhanced by A but also by the F treatment. The K and P concentrations in the fine roots were improved by all three applications. Due to the pH increase Al, Fe and Mn concentrations in the fine roots were decreased by the A and F treatments. S and Zn concentrations showed inconsistent changes over the growing seasons. The results of this study were comparable with those of other studies in Europe and confirm the abilities of the fine roots as indicators of forest nutrition, to some extent more sensitive than the commonly used foliar analysis.     

The Quantity and Turnover of Dead Wood in Permanent Forest Plots in Six Life Zones of Venezuela1

Dead wood can be an important component of the carbon pool in many forests, but few measurements have been made of this pool in tropical forests, To fill this gap, we determined the quantity of dead wood (downed and standing dead) in 25 long-term (up to 30 yr) permanent forest plots located in six different life zones of Venezuela. Downed wood was separated into fine (< 10 cm in diameter) and coarse (≥ 10 cm in diameter) classes, and three decomposition states (sound, intermediate, or rotten). The total quantity of dead wood, averaged by life zone, was lowest in the dry (2.43 Mg/ha), reached a peak in the moist (42.33 Mg/ha) and decreased slightly in the wet (34.50 Mg/ha) life zone. Most of the dead wood was in the standing dead category (about 42–76% of the total). The decomposition state of dead wood in all plots was mostly rotten (45%) or intermediate (44%); there was little sound wood (11%). Turnover rates of dead wood generally ranged between 0.03/yr to 0.52/yr with no clear trend with life zone. The large amount of dead wood in some plots was equivalent to about 20 percent or less of aboveground biomass, indicating that dead wood can represent a significant amount of carbon in these forests.     

Headshields of ephippial Chydorus piger Sars (Cladocera, Chydoridae) females from northern Finnish Lapland: a long period of gamogenesis?

Numerous headshields of ephippial Chydorus piger (currently called Paralona pigra) females were found from the Holocene sediments of Aitajärvi Lake, northern Finnish Lapland (69° 08′ N, 27° 14′ E). Headshields of ephippial females of the genus Chydorus s.l. can be easily identified since their posterior margin is elongated and pointed. According to analysis of fossil cladoceran remains, Chydorus piger lived in the lake throughout the Holocene but was never very common (less than 10% of preserved cladoceran remains). Headshields of ephippial females were found in most samples and they comprised ca 10–30% of all Chydorus piger headshields. No similar phenomenon was met in Chydorus cf. sphaericus which is common up to the most severe arctic conditions. Aitajärvi is situated north of the modern distribution area of Chydorus piger. I suggest that this species reacted to the stress of harsh climatic conditions outside of its distribution area by being gamogenetic during most of the ice-free period. The ephippial headshields could be valuable indicators of severe climatic conditions in pre-Holocene sedimentary environments.     

Lignans of Larix leptolepis

Five lignans have been isolated from wood of Larix leptolepis. They are identified as 1-(4-hydroxy-3-methoxyphenyl)-2-4-[2-formyl-(E)-vinyl]-2-methoxyphenoxy-propane- 1,3-diol, 1-(4-hydroxy-3-methoxyphenyl)-2-2-methoxy-4-[1-(E)-propen-3-ol]-phenoxy- propane-1,3-diol, 1-(4-hydroxy-3-methoxyphenyl)-2-(4-formyl-2-methoxyphenoxy)-propane-1,3-diol, 1,2-bis-(4-hydroxy-3-methoxyphenyl)-propane-1,3-diol and a trilignol, leptolepisol C.     

Environmental and auxin regulation of wood formation involves members of the Aux/IAA gene family in hybrid aspen

Indole acetic acid (IAA/auxin) profoundly affects wood formation but the molecular mechanism of auxin action in this process remains poorly understood. We have cloned cDNAs for eight members of the Aux/IAA gene family from hybrid aspen (Populus tremula L. x Populus tremuloides Michx.) that encode potential mediators of the auxin signal transduction pathway. These genes designated as PttIAA1-PttIAA8 are auxin inducible but differ in their requirement of de novo protein synthesis for auxin induction. The auxin induction of the PttIAA genes is also developmentally controlled as evidenced by the loss of their auxin inducibility during leaf maturation. The PttIAA genes are differentially expressed in the cell types of a developmental gradient comprising the wood-forming tissues. Interestingly, the expression of the PttIAA genes is downregulated during transition of the active cambium into dormancy, a process in which meristematic cells of the cambium lose their sensitivity to auxin. Auxin-regulated developmental reprogramming of wood formation during the induction of tension wood is accompanied by changes in the expression of PttIAA genes. The distinct tissue-specific expression patterns of the auxin inducible PttIAA genes in the cambial region together with the change in expression during dormancy transition and tension wood formation suggest a role for these genes in mediating cambial responses to auxin and xylem development.     

Genomic insights into selection for heterozygous alleles and woody traits in Populus tomentosa

Heterozygous alleles are widespread in outcrossing and clonally propagated woody plants. The variation in heterozygosity that underlies population adaptive evolution and phenotypic variation, however, remains largely unknown. Here, we describe a de novo chromosome-level genome assembly of Populus tomentosa, an economic and ecologically important native tree in northern China. By resequencing 302 natural accessions, we determined that the South subpopulation (Pop_S) encompasses the ancestral strains of P. tomentosa, while the Northwest subpopulation (Pop_NW) and Northeast subpopulation (Pop_NE) experienced different selection pressures during population evolution, resulting in significant population differentiation and a decrease in the extent of heterozygosity. Analysis of heterozygous selective sweep regions (HSSR) suggested that selection for lower heterozygosity contributed to the local adaptation of P. tomentosa by dwindling gene expression and genetic load in the Pop_NW and Pop_NE subpopulations. Genome-wide association studies (GWAS) revealed that 88 single nucleotide polymorphisms (SNPs) within 63 genes are associated with nine wood composition traits. Among them, the selection for the homozygous AA allele in PtoARF8 is associated with reductions in cellulose and hemicellulose contents by attenuating PtoARF8 expression, and the increase in lignin content is attributable to the selection for decreases in exon heterozygosity in PtoLOX3 during adaptive evolution of natural populations. This study provides novel insights into allelic variations in heterozygosity associated with adaptive evolution of P. tomentosa in response to the local environment and identifies a series of key genes for wood component traits, thereby facilitating genomic-based breeding of important traits in perennial woody plants.     

西藏色季拉山急尖长苞冷杉原始林粗木质残体空间格局分析

粗木质残体（Coarse woody debris,CWD）的空间格局反映了森林群落的死亡格局和干扰格局,在一定程度上体现了群落内林木的死亡过程。采用相邻网格法对色季拉山急尖长苞冷杉（Abies georgei var.smithii）原始林1 hm²固定样地内CWD进行调查,从CWD类型、腐烂等级、径级3个方面对CWD空间分布格局进行分析。结果表明：样地内CWD总密度为582株/hm²,倒木占55.33%,是CWD的主要输入形式。CWD密度在腐烂等级上的分布可用多项式拟合（R²=0.9973）,在径级上的分布可用指数衰减模型拟合（R²=0.9746）,且在不同类型、腐烂等级及径级上的分布差异较大。在50 m尺度内,CWD整体表现为小尺度的集群分布和中、大尺度的随机分布。在3种CWD分类中,仅有大枯枝、Ⅰ级腐烂、径级ⅠCWD在小尺度或中尺度表现为较强的集群分布,其余则均以随机分布为主,只是在个别尺度达到或接近集群分布。不同类型CWD间整体关联不显著,只有枯立木与大枯枝在0-21 m尺度内达到显著负关联。CWD空间分布格局是急尖长苞冷杉原始林的重要结构特征,在很大程度上决定着林下植物群落及林型自然更新格局。     

The relationships between brain,serum, and whole blood ChE activity in the wood mouse (Apodemus sylvaticus) and the common shrew (Sorex araneus) after acute sublethal exposure to dimethoate

Abstract

Inhibition of cholinesterase (ChE) activity produced by a single acute intraperitoneal administration of dimethoate was studied in the wood mouse, Apodemus sylvaticus, and the common shrew, Sorex araneus, under laboratory conditions. ChE values from serum and whole blood were compared with those obtained from brain in order to obtain a non-destructive tool for predicting the severity of brain acetylcholinesterase (AChE) inhibition. In addition, serum and brain inhibition following oral exposure to dimethoate was also measured in the wood mouse. Normal ChE activity was higher in the brain and whole blood of the shrews than in wood mice. There was no difference between species in serum ChE activity. Exposure to dimethoate caused a dose-dependent reduction in ChE activity and there was a significant recovery in activity with increasing time after administration. In both species, serum and whole blood were more sensitive than brain for revealing organophosphate-induced ChE inhibition and serum was more sensitive than whole blood. Statistically significant relationships were defined between whole blood and brain ChE activity and between serum and brain ChE activity. Compared with serum, whole blood ChE activity was the more accurate predictor of brain AChE levels. The relationships between brain and serum ChE activity did not appear to be affected by the route of administration of the pesticide.