bluuebunny/crossref_metadata_2025_split huggingface dataset:
Soil, site and management components of variation in species composition of agricultural grasslands in western Norway
Authors: Myklestad Å. 
Published: May 2004

AbstractA partitioning of the total variance in species composition of grasslands associated with increasing fertilizer inputs (unfertilized pastures, artificially fertilized hay meadows and intensively cultivated grassland) in western Norway was undertaken. The partitioning was carried out with (partial) constrained ordinations (canonical correspondence analysis) and associated Monte Carlo permutation tests. Explained variation was high (0·651), with soil chemistry, management and site explaining 0·271, 0·228 and 0·052 of the variation, respectively, and the interaction between soil and management explaining 0·100 of the variation. However, much of the measured soil chemistry was considered to be an effect of management. The soil chemistry variable explaining most variation was extractable P content, associated with high soil extractable P contents in the intensively cultivated grassland due to high fertilizer applications. However, soil extractable P content did not explain differences in species composition when grasslands with smaller differences in fertilizer inputs (meadows vs. pastures) were compared. Total soil C and N contents and C:N ratios explained significant variation between all grassland types. Lowest levels of these variables were measured in the grassland with the highest fertilizer inputs, suggesting that total soil N content cannot be used as a predictor of fertility. Significantly higher soil N contents were measured in grasslands of low productivity, probably due to a low decomposition rate of stress‐tolerant plants and the consequent low availability of soil N and accumulation of soil organic matter. Ellenberg N values reflected soil chemical differences in this study with high Ellenberg N values reflecting high Ca, Mg and P contents and pH values and low total C and N contents and C:N ratios.
Impacts of elevated atmospheric CO2 and temperature on plant community structure of a temperate grassland are modulated by cutting frequency
Authors: Harmens H. , Williams P. D. , Peters S. L. , Bambrick M. T. , Hopkins A. , Ashenden T. W. 
Published: May 2004

AbstractTo determine the impacts of climate change and defoliation on the community structure and plant diversity of a semi‐natural temperate grassland, monoliths of a permanent grassland were exposed to ambient or elevated atmospheric CO2 concentrations (ambient + 235 ppmv) and temperature (ambient + 3°C) from October 1998 to December 2000. The monoliths were subjected to two different cutting frequencies, either two or six cuts per year. The grassland community structure changed during the course of the experiment and was more responsive to changes in management than to changes in climate. Increased cutting frequency stimulated plant diversity by enhancing the number of forb species, but plant diversity was not significantly affected by climate change. The contribution of individual plant species to the vegetation cover revealed species‐specific responses to climate change and cutting frequency, but for most species significant interactions between climate change and cutting frequency were present. There were no clear‐cut effects of treatments on the total annual yield and the proportion of forbs present, as significant interactions between climate change and cutting frequency occurred. It is concluded that differential grassland management will modify plant species‐specific responses to climate change and resulting changes in the botanical composition of mixed‐species, temperate grasslands.
Comparison of a pasture‐based system of milk production on a high rainfall, heavy‐clay soil with that on a lower rainfall, free‐draining soil
Authors: Shalloo L. , Dillon P. , O'Loughlin J. , Rath M. , Wallace M. 
Published: May 2004

AbstractThe objective of this study was to compare the biological and economic efficiency of a seasonal pasture‐based spring calving system of milk production on a high‐rainfall, heavy‐clay soil [Kilmaley (KMY)] to that on a lower‐rainfall free‐draining soil [Moorepark (MPN)] in Ireland. The physical performance data were obtained from a 3‐year study (1998–2000) carried out at both sites. Analysis of the system of milk production at the two sites was undertaken using the Moorepark Dairy System Model. Herbage dry‐matter production was greater at the MPN site with a greater proportion being produced between 1 September and 1 May. On average, over the 3 years, the system of milk production at the MPN site had a higher stocking rate (2·34 vs. 1·89 cows ha−1), higher milk production per cow (6421 vs. 5781 kg per cow), longer grazing season (250 vs. 149 d) and a higher proportion of the diet of the herd from grazed grass (0·70 vs. 0·40) than at KMY. Economic analysis showed that, in a 468 100 kg European Union milk quota scenario, the profitability at the MPN site was €28 417 greater than at the KMY site. At similar milk production per cow it was €19 138 greater. Monte Carlo simulation showed that the MPN site was stochastically dominant over the KMY site. Sensitivity analyses showed that farm profit was most sensitive to changes in milk price. The results also indicated that milk production in the future may not be sustainable economically on high‐rainfall, heavy‐clay soils in Ireland.
Comparison between two modified methods of neutral‐detergent fibre analysis
Authors: Gustavsson A.‐M. , Martinsson K. 
Published: May 2004

AbstractWhen describing the methods of analysis of neutral‐detergent fibre (NDF) it is valuable to know if different modifications of the standard method of analysis give the same absolute results or if the analysing method has to be specified. In this study two modifications of the standard method were compared, a 16‐h oven technique and a filter‐bag technique. The comparisons were conducted using thirty‐two timothy (Phleum pratense L.) and thirty‐two red clover (Trifolium pratense L.) samples. The study showed that both methods ranked the forage samples in the same relative order and had good accuracy. However, the NDF concentrations for the filter‐bag system were on average 7·8 g kg−1 DM higher for the red clover samples and 39·7 g kg−1 DM higher for the timothy samples. The difference in concentration of NDF for the red clover samples was smaller than the field variation and the daily change in NDF concentration, but in timothy the difference was four to five times larger than the field variation and the mean daily changes in NDF concentration. The study shows that it is important to specify the method of analysis for NDF when analysing timothy samples but not red clover samples, and that for this dataset it was possible to use a correction constant to recalculate the results from one method to the other.
Microbial communities in the phyllosphere of grasses on fenland at different intensities of management
Authors: Behrendt U. , Stauber T. , Müller T. 
Published: May 2004

AbstractThe effects of changes from conventional grassland management on fenland in Germany to extensification due to reduced fertilizer inputs and cutting frequency on the microbial colonization in the phyllosphere were investigated. A delay in the first cut for silage and hay, required by a nature conservation programme, was accompanied by the senescence of grasses which significantly influenced certain microbial groups. Heterotrophic bacteria, aerobic and anaerobic spore‐formers, as well as filamentous fungi, showed an increase in population densities on the mature herbage of the later cuts. Differences in the rate of fertilizer application and cutting frequency, which had an effect on the dry‐matter yield, also influenced the population density of heterotrophic bacteria and, in certain circumstances, that of filamentous fungi. Chemical measures of forage quality were highly correlated with the population density of microbial groups and with the maturity of the herbage. In contrast to these results, the population dynamics of further groups of micro‐organisms (yeasts, Micrococcaceae, listeria) did not show any relationship with pasture management.
Discrimination of morphological findings in dentine from osteogenesis imperfecta patients using combinations of polarized light microscopy, microradiograhpy and scanning electron microscopy
Authors: Lindau B. , Dietz W. , Lundgren T. , Storhaug K. , Norén J.G. 
Published: May 2004

Objectives. The aim of this study was to investigate the morphological appearance of dentine in teeth from individuals with osteogenesis imperfecta type I, III and IV using different histological techniques, and to correlate morphological findings to different types of osteogenesis imperfecta. Sample and methods. Extracted or exfoliated primary and permanent teeth were collected from 15 patients with the osteogenesis imperfecta diagnoses I, III or IV, with or without the additional diagnosis dentinogenesis imperfecta. Ground and decalcified sections were prepared from the teeth. Histo‐morphological studies of the dentine were performed utilizing light and polarized light microscopy, microradiography and scanning electron microscopy. Results. Characteristic findings were irregular tubules, remnants of capillary inclusions and obliterated pulps. All types of osteogenesis imperfecta exhibited similar types of dentine aberrations, but patients with type III or IV had a higher frequency of aberrations when compared to type I. Conclusions. The combination of either polarized light microscopy or micro‐radiography, together with scanning electron microscopy, gave the most amount of morphological information from dentine samples. In addition, aberrations in dentine structure were more clearly observable. Light microscopy was not critical for the analyses.
Calmodulin activity and cAMP signalling modulate growth and apical secretion in pollen tubes
Authors: Rato Cláudia , Monteiro David , Hepler Peter K. , Malhó Rui 
Published: May 2004

SummaryOur present understanding implicates both calmodulin (CaM) and 3′,5′‐cyclicAMP (cAMP) in the regulation of pollen tube growth. However, downstream molecules of these signalling pathways and the cellular processes they modulate remain largely unknown. In order to elucidate the role of CaM, we mapped its activity in growing pollen tubes. 2‐chloro‐(ε‐amino‐Lys75)‐[6‐4‐(N,N′‐diethylaminophenyl)‐1,3,5‐triazin‐4‐yl]‐calmodulin (TA‐CaM) and fluorescein‐calmodulin (FL‐CaM), fluorescent analogues of CaM, were loaded into pollen tubes and CaM activity was mapped by fluorescence ratio imaging. It was found that CaM activity exhibits a tip‐focused gradient, similar to the distribution of cytosolic‐free calcium ([Ca2+]c). In long pollen tubes, apical CaM activity was also found to oscillate with a period similar to [Ca2+]c (40–80 sec). This oscillatory behaviour was not observed in small pollen tubes or in tubes that had stopped growing. Changes in CaM activity within the dome of the pollen tube apex resulting from the photolysis of caged photolysis of RS‐20 (a peptide antagonist of CaM) induced re‐orientation of the growth axis, suggesting that CaM is also involved in the guidance mechanism. CaM activity was strongly modulated by intracellular changes in cAMP (induced by activators and antagonists of adenylyl cyclase). These results indicate that the action of this protein is dependent not solely on [Ca2+]c but also on a cross‐talk with other signalling pathways. A putative target of this cross‐talk is the secretory machinery as observed in pollen tubes loaded with the FM (N‐(3‐triethylammoniumpropyl)‐4‐(4‐dibutylamino)styryl)pyridinium dibromide 1‐43 dye and exposed to different antagonists and activators of these molecules. Our data thus suggest that pollen tube growth and orientation depend on an intricate cross‐talk between multiple signalling pathways in which CaM is a key element.
Senescence‐induced expression of cytokinin reverses pistil abortion during maize flower development
Authors: Young Todd E. , Giesler‐Lee Jane , Gallie Daniel R. 
Published: May 2004

SummaryMaize is a monoecious species that produces imperfect (unisexual), highly derived flowers called florets. Within the spikelet, the basic repeating unit of the maize inflorescence, the spikelet meristem gives rise to an upper and a lower floret. Although initially bisexual, floret unisexuality is established through selective organ elimination. In addition, the lower floret of each ear spikelet is aborted early in its development, leaving the upper floret to mature as the only pistillate floret. Expression from the cytokinin‐synthesizing isopentenyl transferase (IPT) enzyme under the control of the Arabidopsis senescence‐inducible promoter SAG (senescence associated gene)12 was observed during early maize floret development. Moreover, the lower floret was rescued from abortion, resulting in two functional florets per spikelet. The pistil in each floret was fertile, but the spikelet produced just one kernel composed of a fused endosperm with two viable embryos. The two embryos were genetically distinct, indicating that they had arisen from independent fertilization events. These results suggest that cytokinin can determine pistil cell fate during maize floret development.
The Etched1 gene of Zea mays (L.) encodes a zinc ribbon protein that belongs to the transcriptionally active chromosome (TAC) of plastids and is similar to the transcription factor TFIIS
Authors: Da Costa e Silva Oswaldo , Lorbiecke René , Garg Preeti , Müller Lenard , Waßmann Martina , Lauert Patricia , Scanlon Mike , Hsia An‐Ping , Schnable Patrick S. , Krupinska Karin , Wienand Udo 
Published: May 2004

Summary Etched1 (et1) is a pleiotropic, recessive mutation of maize that causes fissured and cracked mature kernels and virescent seedlings. Microscopic examinations of the et1 phenotype revealed an aberrant plastid development in mutant kernels and mutant leaves. Here, we report on the cloning of the et1 gene by transposon tagging, the localization of the gene product in chloroplasts, and its putative function in the plastid transcriptional apparatus. Several alleles of Mutator (Mu)‐induced et1 mutants, the et1‐reference (et1‐R) mutant, and Et1 wild‐type were cloned and analyzed at the molecular level. Northern analyses with wild‐type plants revealed that Et1 transcripts are present in kernels, leaves, and other types of tissue, and no Et1 expression could be detected in the et1 mutants analyzed. The ET1 protein is imported by chloroplasts and has been immunologically detected in transcriptionally active chromosome (TAC) fractions derived from chloroplasts. Accordingly, the relative transcriptional activity of TAC fractions was significantly reduced in chloroplasts of et1‐R plants. ET1 is the first zinc ribbon (ZR) protein shown to be targeted to plastids. With regard to its localization and its striking structural similarity to the eukaryotic transcription elongation factor TFIIS, it is feasible that ET1 functions in plastid transcription elongation by reactivation of arrested RNA polymerases.
Interaction of the plant glycine‐rich RNA‐binding protein MA16 with a novel nucleolar DEAD box RNA helicase protein fromZea mays
Authors: Gendra Elisenda , Moreno Alicia , Albà M. Mar , Pages Montserrat 
Published: May 2004

SummaryThe maize RNA‐binding MA16 protein is a developmentally and environmentally regulated nucleolar protein that interacts with RNAs through complex association with several proteins. By using yeast two‐hybrid screening, we identified a DEAD box RNA helicase protein fromZea maysthat interacted with MA16, which we namedZ. maysDEAD boxRNAhelicase1(ZmDRH1). The sequence of ZmDRH1 includes the eight RNA helicase motifs and two glycine‐rich regions with arginine–glycine‐rich (RGG) boxes at the amino (N)‐ and carboxy (C)‐termini of the protein. Both MA16 and ZmDRH1 were located in the nucleus and nucleolus, and analysis of the sequence determinants for their cellular localization revealed that the region containing the RGG motifs in both proteins was necessary for nuclear/nucleolar localization The two domains of MA16, the RNA recognition motif (RRM) and the RGG, were tested for molecular interaction with ZmDRH1. MA16 specifically interacted with ZmDRH1 through the RRM domain. A number of plant proteins and vertebrate p68/p72 RNA helicases showed evolutionary proximity to ZmDRH1. In addition, like p68, ZmDRH1 was able to interact with fibrillarin. Our data suggest that MA16, fibrillarin, and ZmDRH1 may be part of a ribonucleoprotein complex involved in ribosomal RNA (rRNA) metabolism.
Non‐invasive online detection of nitric oxide from plants and some other organisms by mass spectrometry
Authors: Conrath Uwe , Amoroso Gabriele , Köhle Harald , Sültemeyer Dieter F. 
Published: May 2004

SummaryAs nitric oxide (NO) is a key messenger in many organisms, reliable techniques for the detection of NO are essential. Here, it is shown that a combination of membrane inlet mass spectrometry (MIMS) and restriction capillary inlet mass spectrometry (RIMS) allows for the fast, specific, and non‐invasive online detection of NO that has been emitted from tissue cultures of diverse organisms, or from whole plants. As an advantage over other NO assays, MIMS/RIMS discriminates nitrogen isotopes and simultaneously measures NO and O2 (and other gases) from the same sample. MIMS/RIMS technology may thus help to identify the source of gaseous NO in cells, and elucidate the relationship between primary gas metabolism and NO formation. Using RIMS, it is demonstrated that the novel fungicide F 500® triggers NO production in plants.
The Rad17 homologue of Arabidopsis is involved in the regulation of DNA damage repair and homologous recombination
Authors: Heitzeberg Fabian , Chen I‐Peng , Hartung Frank , Orel Nadiya , Angelis Karel J. , Puchta Holger 
Published: May 2004

SummaryRad17 is involved in DNA checkpoint control in yeast and human cells. A homologue of this gene as well as other genes of the pathway (the 9‐1‐1 complex) are present in Arabidopsis and share conserved sequence domains with their yeast and human counterparts. DNA‐damaging agents induce AtRAD17 transcriptionally. AtRAD17 mutants show increased sensitivity to the DNA‐damaging chemicals bleomycin and mitomycin C (MMC), which can be reversed by complementation, suggesting that the loss of function of Rad17 disturbs DNA repair in plant cells. Our results are further confirmed by the phenotype of a mutant of the 9‐1‐1 complex (Rad9), which is also sensitive to the same chemicals. AtRAD9 and AtRAD17 seem to be epistatic as the double mutant is not more sensitive to the chemicals than the single mutants. The mutants show a delay in the general repair of double‐strand breaks (DSBs). However, frequencies of intrachromosomal homologous recombination (HR) are enhanced. Nevertheless, the mutants are proficient for a further induction of HR by genotoxic stresses. Our results indicate that a mutant Rad17 pathway is associated with a general deregulation of DNA repair, which seems to be correlated with a deficiency in non‐homologous DSB repair.
Two TIR:NB:LRR genes are required to specify resistance to Peronospora parasitica isolate Cala2 in Arabidopsis
Authors: Sinapidou Eva , Williams Kevin , Nott Lucy , Bahkt Saleha , Tör Mahmut , Crute Ian , Bittner‐Eddy Peter , Beynon Jim 
Published: May 2004

SummaryResistance responses that plants deploy in defence against pathogens are often triggered following a recognition event mediated by resistance (R) genes. The encoded R proteins usually contain a nucleotide‐binding site (NB) and a leucine‐rich repeat (LRR) domain. They are further classified into those that contain an N‐terminal coiled coil (CC) motif or a Toll interleukin receptor (TIR) domain. Such R genes, when transferred into a susceptible plant of the same or closely related species, usually impart full resistance capability. We have used map‐based cloning and mutation analysis to study the recognition of Peronospora parasitica (RPP)2 (At) locus in Arabidopsis accession Columbia (Col‐0), which is a determinant of specific recognition of P. parasitica (At) isolate Cala2. Genetic mapping located RPP2 to a 200‐kb interval on chromosome 4, which contained four adjacent TIR:NB:LRR genes. Mutational analysis revealed three classes of genes involved in specifying resistance to Cala2. One class, which resulted in pleiotropic effects on resistance to other P. parasitica (At) isolates, was unlinked to the RPP2 locus; this class included AtSGT1b. The other two classes were mapped within the interval and were specific to Cala2 resistance. Representatives of each of these classes were sequenced, and mutations were found in one or the other of two (RPP2A and RPP2B) of the four TIR:NB:LRR genes. RPP2A and RPP2B complemented their specific mutations, but failed to impart resistance when present alone, and it is concluded that both genes are essential determinants for isolate‐specific recognition of Cala2. RPP2A has an unusual structure with a short LRR domain at the C‐terminus, preceded by two potential but incomplete TIR:NB domains. In addition, the RPP2A LRR domain lacks conserved motifs found in all but three other TIR:NB:LRR class proteins. In contrast, RPP2B has a complete TIR:NB:LRR structure. It is concluded that RPP2A and RPP2B cooperate to specify Cala2 resistance by providing recognition or signalling functions lacked by either partner protein.
Identification of cold‐inducible downstream genes of the Arabidopsis DREB1A/CBF3 transcriptional factor using two microarray systems
Authors: Maruyama Kyonoshin , Sakuma Yoh , Kasuga Mie , Ito Yusuke , Seki Motoaki , Goda Hideki , Shimada Yukihisa , Yoshida Shigeo , Shinozaki Kazuo , Yamaguchi‐Shinozaki Kazuko 
Published: May 2004

SummaryThe transcriptional factor DREB/CBF (dehydration‐responsive element/C‐repeat‐binding) specifically interacts with the dehydration‐responsive element (DRE)/C‐repeat (CRT) cis‐acting element (A/GCCGAC) and controls the expression of many stress‐inducible genes in Arabidopsis. Transgenic plants overexpressing DREB1A showed activated expression of many stress‐inducible genes and improved tolerance to not only drought, salinity, and freezing but also growth retardation. We searched for downstream genes in transgenic plants overexpressing DREB1A using the full‐length cDNA microarray and Affymetrix GeneChip array. We confirmed candidate genes selected by array analyses using RNA gel blot and identified 38 genes as the DREB1A downstream genes, including 20 unreported new downstream genes. Many of the products of these genes were proteins known to function against stress and were probably responsible for the stress tolerance of the transgenic plants. The downstream genes also included genes for protein factors involved in further regulation of signal transduction and gene expression in response to stress. The identified genes were classified into direct downstream genes of DREB1A and the others based on their expression patterns in response to cold stress. We also searched for conserved sequences in the promoter regions of the direct downstream genes and found A/GCCGACNT in their promoter regions from −51 to −450 as a consensus DRE. The recombinant DREB1A protein bound to A/GCCGACNT more efficiently than to A/GCCGACNA/G/C.