The observer effect in plant science
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Plants have been widely documented to respond to mechanical stimuli such as wind and touch. Well-known and long-studied examples of these are carnivorous plants (e.g. Darwin, 1893), but nonspecialized plants are also sensitive and responsive to mechanical perturbation. Studies on this phenomenon, called ‘thigmomorphogenesis’ (Jaffe, 1973), have been conducted for several decades, revealing complex signaling and response pathways (Braam, 2005). Common thigmomorphogenetic responses include altered shoot elongation vs radial expansion ratios, delayed flowering, changes in chlorophyll content, etc. (see Biddington, 1986 and Cahill et al., 2002 for a review and a concise overview, respectively). In nature, such changes usually occur in response to wind and as a result of contact with neighbouring plants. Humans can unwillingly mimic these effects when studying plants, as several studies have shown that the mere act of touching plants by hand can have significant effects (Braam & Davis, 1990; Cahill et al., 2001). Moreover, in a considerable number of plant studies, measurements are not limited to touching plant tissue but include destructive sampling of leaves, roots, etc. It is apparent that if such (repeated) plant measurements, whether destructive or nondestructive, affect plant functioning, this could have far-reaching implications. Nevertheless, the attention given to such ‘observer effects’ in plant science has been limited. If studying plants indeed implies involuntarily altering their morphology and/or physiology, then two main problems could arise. First, in studies on the state of nature (e.g. ozone damage in European forests, Ferretti et al., 2007), the presence of an observer effect could cause such assessments to deviate from reality, leading to erroneous conclusions. Second, in studies with an experimental treatment, a further problem arises if handling plants results in different effects in the different treatments (as already suggested by Cahill et al., 2001). Such a treatment × handling interaction would again distort the study's results and conclusions, as it implies inflation or understatement of the treatment effects. As treatment studies are often future oriented (e.g. investigating the effects of elevated CO2 concentrations or increased temperatures), this could subsequently lead to an incorrect impact assessment of several global changes. As an example from an actual experiment, we processed data from POP-EUROFACE in Central Italy (42°22¢N, 11°48¢E), a large-scale experiment for studying the long-term effects of elevated CO2 concentrations on carbon sequestration and bio-energy production in a short rotation coppice. An overview of the set-up can be found in Scarascia-Mugnozza et al. (2006). During six consecutive years (1999–2004), poplars were exposed to elevated CO2 concentrations (550 ppm) in three free air CO2 enrichment (FACE) areas, and three areas with ambient CO2 concentrations served as a control. Each area was divided into six sectors that were planted with three different poplar species (Populus alba L., P. nigra L. and P. × euramericana). Throughout these 6 yr, over 10 different research teams carried out measurements in this plantation, from the leaf level up to the canopy scale. Most of the wide array of common ecological measurements took place in ‘permanent growth plots’ (PGPs), and consisted of both destructive (e.g. leaf chlorophyll, nitrogen, rubisco, leaf area, soil coring) and nondestructive (e.g. tree diameter, height, canopy light transmission) measurements, with a similar intensity in each year. The PGPs consisted of a group of six adjacent trees within each sector, surrounded by at least one row of trees of the same genotype and treatment (Supplementary material Fig. S1). To assess the occurrence of observer effects, trees with very limited exposure to handling were randomly selected from the remaining poplars inside each sector (i.e. 18 trees during the first rotation (until 2001), and nine trees during the second rotation (until 2004)). In this study, we compared poplar biomass production (scaled up from stem diameter via allometric relations, cf. Calfapietra et al., 2003; Liberloo et al., 2005, 2006) inside and outside the permanent growth plots, to assess the following: whether an observer effect was detectable; whether there was an interaction of this effect with the CO2 treatment; whether the three poplar species responded differently to handling; and whether any of the observer effects changed over time. To this end, data sets from 2000, 2001, 2003 and 2004 were used. Stem diameter was the only measurement consistently made inside and outside PGPs during the course of the experiment, but is considered a suitable parameter for a general assessment of observer effects because of its nondestructive nature and its use as a proxy for tree vigour and health. Data were examined in sas (SAS 9.1; SAS Institute, Cary, NC, USA), first using an analysis of variance (ANOVA) with repeated measures in time on the biomass data (log transformed for normalisation) to test the significance (P < 0.05) of observer effects. The design was a randomized complete block, with CO2 treatment, species, year and plot identity (PGP or non-PGP) as fixed factors, block (i.e. the combination of one control and one treatment area) as a random factor, and plot as the unit of replication. Upon confirmation of the significance of observer effects, an identical-repeated measures ANOVA was then performed on the observer effect itself (i.e. the percental difference in above-ground biomass between PGPs and non-PGPs (these data had a normal distribution after removal of one outlier)), to test specifically for effects of treatment, species or year (fixed factors). An a posteriori comparison of means was performed with the Bonferroni correction for multiple comparisons. The analysis showed that trees inside and outside PGPs differed significantly (P < 0.001), with biomass reduced by up to 50% because of handling (Fig. 1). The observer effect differed between species (P < 0.01), with significantly lower adverse effects of handling in P. alba compared with the other two species (P < 0.05 after correction). Observer effects were furthermore strongly affected by the measurement year (P < 0.001) as they only reached significance in the last 2 yr of the study (2003–2004). Finally, a posteriori comparison revealed a trend towards differences in the size of observer effects in both treatments for P. × euramericana (P = 0.10 after correction), which was also visible in Fig. 1. Other factors and interactions were not significant. The percental difference in above-ground biomass (calculated from stem diameter via allometric relationships) between trees inside and outside permanent growth plots (PGPs), growing under ambient (open symbols, dashed line) or elevated (closed symbols, solid line) CO2 concentrations. Three Populus species are depicted: (a) P. alba; (b) P. nigra; and (c) P. × euramericana. Only averages and standard errors are shown. Symbols are slightly shifted, with respect to the x-axis, for clarity. The experiment that we scanned for observer effects yielded several interesting results. In general, handling was found to decrease productivity and did so by proportionally the same extent under treatment and control conditions, even though there were indications that the observer effect differed somewhat between treatments for one species. Our data thus provide further evidence to disprove the assumption of researchers as ‘benign observers’, as indeed the act of conducting an experiment can alter the experimental results (Cahill et al., 2001). The general absence of observer effects in 2000 and 2001, and the markedly steep decline in biomass inside vs outside PGPs in the last 2 yr of the study, furthermore suggest that adverse handling effects can build up (even across coppicing events), as the measurement intensity was similar in all years. Such an effect would be of particular importance in long-term experiments in which the same plots and plants are sampled continuously (similar to POP-EUROFACE). The recent trend towards such long-term studies (e.g. Wullschleger & Hanson, 2006; Mohan et al., 2007), invoked by their great scientific value, especially in determining impacts of global changes beyond single growing seasons, could therefore lead to a growing relevance of observer effects. It must be noted that, because there was no general treatment × handling interaction, conclusions of the POP-EUROFACE studies regarding effects of elevated CO2 concentrations on poplar growth were probably correct. Apart from direct effects of measuring, observers can also cause indirect effects that affect plant functioning. Among these are altered incidence of herbivory or plant diseases (Latimer & Oetting, 1999; Niesenbaum et al., 2006), soil compaction (Hik et al., 2003; Andres-Abellan et al., 2005) and changes in light conditions (Cahill et al., 2001). An indirect effect that probably caused a proportion of the observer effect in the POP-EUROFACE experiment was the combination of a windy site and the presence of scaffolding towers, causing mechanical damage to (predominantly) the PGP trees. We rule out that observer effects were solely attributable to the towers, as these were located at one side of the PGPs (Supplementary material Fig. S1) and therefore did not impact all PGP trees (affirmed by visual inspection of the damaged tree tops). As significant biomass reduction was found throughout the PGPs, negative direct impacts of measurements and sampling must have contributed to the observed growth reduction. The multitude of possible observer effects, both direct and indirect, renders it extremely difficult to predict their combined outcome. Moreover, sampling has been documented to affect different species in different ways (Hik et al., 2003), which was confirmed by the POP-EUROFACE data. This further increases the difficulties of quantifying observer effects, and hence makes it paramount to avoid or minimize such effects in the first place. In animal studies, and especially those concerned with behaviour, observer effects have long been known and acknowledged (Wade et al., 2005). In that field of research, avoidance is also deemed the best strategy for coping with observer effects rather than taking these into account somehow (e.g. Baker & McGuffin, 2007). In plant science, noninvasive techniques exist as an alternative to certain destructive measurements (such as leaf area determination). However, accuracy problems often make these alternatives less reliable (e.g. Broadhead et al., 2003). In many cases it is unavoidable that researchers do exert an influence, as, for example, cuvette measurements (which can damage leaves) provide data that are often essential but currently impossible to collect in less intrusive ways. Given the constraints imposed by the measurement technology currently available, the most appropriate solution to minimize observer effects seems to be to lower the measurement intensity. This can be achieved either by taking fewer samples per unit of time, or by spreading out the measurements over a larger number of study objects (plants, communities, etc.). Two main problems are associated with this. In the first case, reducing the number of samples would lower the statistical power, whereas the second proposed solution goes against the often-adhered researcher's philosophy to make full use of the money granted by maximizing the amount of data collected per unit of currency funded. Nevertheless, to avoid the risk of the experimental results becoming flawed, either of our two proposed solutions should be considered. Of course, only in hindsight can it be confidently stated whether the applied intensity affected plant functioning. It would nevertheless be prudent to design all sampling protocols for minimal disturbance while maintaining a statistically adequate number of data samples. This is especially relevant for treatment-type studies, in which the same limited number of experimental objects are sampled continuously and which therefore seem much more prone to oversampling than state-of-nature studies that usually have a lower sampling intensity. Field experiments regarding observer effects have almost uniquely been conducted to test the ‘herbivory uncertainty principle’, which states that researcher visitation and plant measurements may alter herbivore and pathogen damage (Cahill et al., 2001; Schnitzer et al., 2002). The manipulations in these type of experiments can be considered as mild, as they consist mainly of visual observations and height measurements. Even under these conditions were observer effects, although not consistently (e.g. Bradley et al., 2003; Cahill et al., 2004). We have demonstrated that in a long-term experiment with frequent and invasive measurements, observer effects are potentially larger (although the largest effects were observed only in the later stages). To elucidate the uncertainties associated with observer effects, research is needed: to unveil the generality of observer effects (i.e. whether they are more outspoken in certain ecosystems (e.g. tundra) and species or functional groups than in others); to clarify the relationship between measurement intensity and effect (i.e. is there a dose–response relationship (linear or otherwise) or are there thresholds?); to assess which types of measurements have the largest impact; and to uncover which plant process is the most sensitive to handling. To help resolve these important questions, we advise leaving part of any experiment unsampled, allowing for an a posteriori assessment of observer effects (such as for POP-EUROFACE). From contacts with international colleagues, we understand that a majority of scientists dealing with long-term experiments are aware of the existence of observer effects. However, by quantifying these effects, we have shown that the often underlying assumption that they are negligible is not necessarily true. Observer effects should therefore always be considered in setting up new experiments and drawing up sampling strategies, by focusing on minimizing disturbance. Such considerations are, in our eyes, vital to further plant research. Indeed, the issue of observer effects is a genuine concern, which will not be resolved by ignoring its existence. H. J. De Boeck holds a grant from the Institute for the Promotion of Innovation through Science and Technology in Flanders (IWT-Vlaanderen). M. Liberloo and B. Gielen are postdoctoral research associates of the Fund for Scientific Research – Flanders. POP-EUROFACE was supported by EU-POPFACE (ENV4-CT97-0657), EU-EUROFACE (EVR1-CT-2002-40027), the Center of Excellence ‘Forest and Climate’ (Italian Ministry of University and Research), and the Italy-USA Bilateral Project on Climate Change of the Italian Ministry of Environment. We thank V. Sluydts and S. Van Dongen for statistical advice. The following supplementary material is available for this article online: Fig. S1 Layout of the POP-EUROFACE plantation with two poplar fields, divided by a country road, and six experimental areas (black = free air CO2 enrichment (FACE)). This material is available as part of the online article from: http://www.blackwell-synergy.com/doi/abs/10.1111/j.1469-8137.2007.02329.x (This link will take you to the article abstract). Please note: Blackwell Publishing are not responsible for the content or functionality of any supplementary materials supplied by the authors. Any queries (other than missing material) should be directed to the journal at New Phytologist Central Office. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.Infectivity
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In a soil bioassay, adult Deroceras reticulatum (Stylommatophora: Limacidae) and three different weight-classes of young Arion lusitanicus (Stylommatophora: Arionidae) were exposed to a single dosage (170 dauer larvae per g of soil) of the nematode Phasmarhabditis hermaphrodita monoxenically associated with the bacterium Moraxella osloensis. Groups of 10 slugs were continuously exposed to nematodes for 4 days, and then transferred individually to Petri-dishes containing a disc of Chinese cabbage as food. Food consumption—measured by image analysis—and slug mortality were recorded daily for 10 days. Food consumption was inhibited in both slug species tested. D. reticulatum stopped feeding 6 days after the start of nematode treatment, while all A. lusitanicus continued to feed. However, in the three weight-classes of A. lusitanicus (0.15 g, 0.24 g, 0.45 g), food consumption was reduced by at least 50 %. The greatest reduction in feeding, nearly 90 %, was noted in the smallest A. lusitanicus. The nematodes successfully killed D. reticulatum but were less efficient at killing young A. lusitanicus. At the end of the experiment, mortality was highest in D. reticultatum (98 %) and the smallest weight-class of A. lusitanicus (47 %). There was almost no mortality in the largest weight-class of A. lusitanicus treated with nematodes. P. hermaphrodita associated with M. osloensis can thus be considered as a biological control agent for young stages of A. lusitanicus for its effect as a feeding inhibitor, rather than for its ability to kill the slugs.
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In response to DNA damage, p53 undergoes post-translational modifications (including acetylation) that are critical for its transcriptional activity. However, the mechanism by which p53 acetylation is regulated is still unclear. Here, we describe an essential role for HLA-B-associated transcript 3 (Bat3)/Scythe in controlling the acetylation of p53 required for DNA damage responses. Depletion of Bat3 from human and mouse cells markedly impairs p53-mediated transactivation of its target genes Puma and p21 . Although DNA damage-induced phosphorylation, stabilization, and nuclear accumulation of p53 are not significantly affected by Bat3 depletion, p53 acetylation is almost completely abolished. Bat3 forms a complex with p300, and an increased amount of Bat3 enhances the recruitment of p53 to p300 and facilitates subsequent p53 acetylation. In contrast, Bat3-depleted cells show reduced p53–p300 complex formation and decreased p53 acetylation. Furthermore, consistent with our in vitro findings, thymocytes from Bat3-deficient mice exhibit reduced induction of puma and p21, and are resistant to DNA damage-induced apoptosis in vivo. Our data indicate that Bat3 is a novel and essential regulator of p53-mediated responses to genotoxic stress, and that Bat3 controls DNA damage-induced acetylation of p53.
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In the present study, several multivariate analyses were carried out to assess the taxonomic relationships among European species of the genus Anthoxanthum. A total of 1787 Anthoxanthum specimens representing all European taxa were analyzed. Thirty macro-morphological (13 quantitative and 17 qualitative) and 29 micro-morphological (7 quantitative and 22 qualitative) characters were considered. First, resemblances between specimens were established independently for macro- and micro-morphological characters using Gower's similarity coefficient, and were represented by means of principal coordinates and cluster analyses. Subsequently, different multivariate analyses were applied to quantitative and qualitative macromorphological data to determine the most discriminant characters and the accuracy of the present taxonomic structure of the genus. Finally, dissimilarities among groups of individuals -species and populations- were estimated using the information radius measure and then represented in different dendrograms. Within annuals, Anthoxanthum gracile is clearly differentiated morphologically, yet no compelling morphological differentiation can be found between Anthoxanthum aristatum and Anthoxanthum ovatum. Moreover, the definition of subspecies in the annual taxa is not supported by our results. Then, within perennials, although the morphological relationships among Anthoxanthum amarum, Anthoxanthum odoratum and Anthoxanthum alpinum have also been resolved, further research is needed to assess the taxonomic position of the Macaronesian endemic Anthoxanthum maderense.
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Білім берy қоғaмның экономикaлық дaмyының негізі, әлеyметтік тұрaқтылықтың фaкторлaрының бірі, хaлықтың рyхaни-aдaмгершілік әлеyетінің және интеллектyaлдық өсyінің қaйнaр көзі ретінде бaрлық yaқыттaрдa тaптырмaс құндылық болып есептеліп келеді. Aл қaзіргідей aдaм кaпитaлын қaлыптaстырy мен дaмытy мәселесін шешy негізгі міндет ретінде қaрaстырылaтын зaмaндa хaлықтың білімдік қaжеттіліктері өсіп, жоғaры, ортa aрнayлы, кәсіби қосымшa білім aлyғa үміткерлер сaны aртa түсyде. Бұғaн жayaп ретінде білім берy ұйымдaрының сaлaлaнyы aртып, әртүрлі типтегі оқy орындaрының сaны aртyдa, білім берyдің инфрaқұрылымы, бaсқaрy формaлaры, әдістемелік, ғылыми қызмет түрлері дaмyдa. Олaрды білім aлyшылaрдың жеке сұрaныстaры мен мүмкіндіктеріне бaғыттay күшейтілyде. Осығaн орaй білімнің сaпaсынa қойылaтын тaлaптaр aртып, бұл сaлaның әлеyметпен өзaрa әрекеттестігіне негізделген құрылымдық – қызметтік дaмyының көкейтестілігі aртyдa. Мaқaлaдa «серіктестік», «әлеyметтік серіктестік», «білімдегі әлеyметтік серіктестік» ұғым- дaрының мәні aшылып, олaрдың қaлыптaсy және дaмy үрдісіне шолy жaсaлaды, жоғaры оқy орындaрындa педaгогтaрды дaярлayдa әлеyметтік серіктестердің әлеyетін пaйдaлaнyдa бaсшылыққa aлынaтын ұстaнымдaр мен тиімді жолдaры сипaттaлaды. Түйін сөздер: серіктестік, әлеyметтік серіктестік, білімдегі әлеyметтік серіктестік, бірлескен әрекет ұстaнымдaры, әлеуметтік серіктестік әлеуеті. Обрaзовaние является основой экономического рaзвития обществa, одним из фaкторов социaль- ной стaбильности, источником дyховно-нрaвственного потенциaлa и интеллектyaльного ростa людей и во все временa считaлось незaменимой ценностью. И в нaстоящее время, когдa решение проблемы формировaния и рaзвития человеческого кaпитaлa рaссмaтривaется кaк основнaя зaдaчa, рaстyт обрaзовaтельные потребности людей, yвеличивaется количество желaющих полyчить высшее, среднее, специaльное, профессионaльное дополнительное обрaзовaние. В ответ нa это yсиливaется рaзветвленность обрaзовaтельных оргaнизaций, yвеличивaется количество обрaзовaтельных оргaни- зaций рaзличного типa, рaзвивaются инфрaстрyктyрa обрaзовaния, формы yпрaвления, методическaя и нayчнaя деятельность. Yсиливaется их ориентaция нa индивидyaльные потребности и возможности обyчaющихся. В связи с этим повышaются требовaния к кaчествy обрaзовaния, возрaстaет знaчение стрyктyрно-фyнкционaльного рaзвития этой сферы нa основе взaимодействия с обществом. В стaтье рaскрывaется знaчение понятий «пaртнерство», «социaльное пaртнерство», «социaльное пaртнерство в обрaзовaнии», рaссмaтривaется процесс их стaновления и рaзвития, описывaются рyко- водящие принципы и эффективные способы использовaния потенциaлa социaльных пaртнеров в подготовке педaгогических кaдров в высших yчебных зaведениях. Ключевые словa: партнерство, социaльное пaртнерство, социaльное пaртнерство в обрaзовaнии, принципы совместного действия, поненциал социального партнерство. Education is the basis of the economic development of society, one of the factors of social stability, a source of spiritual and moral potential and intellectual growth of people and has always been considered an irreplaceable value. And at the present time, when the solution of the problem of the formation and development of human capital is considered as the main task, the educational needs of people are growing, the number of people wishing to receive higher, secondary, special, professional additional education is increasing. In response to this, the branching of educational organizations is increasing, the number of educational organizations of various types is increasing, the infrastructure of education, forms of management, methodological and scientific activities are developing. Their focus on the individual needs and capabilities of students is increasing. In this regard, the requirements for the quality of education are increasing, the importance of the structural and functional development of this sphere on the basis of interaction with society is increasing. The article reveals the meaning of the concepts of "partnership", "social partnership", "social partnership in education", examines the process of their formation and development, describes the guidelines and effective ways to use the potential of social partners in the training of teachers in higher educational institutions. Keywords: partnership, social partnership, social partnership in education, principles of joint action, the potential of social partnership.
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HLA-B-associated transcript 3 (BAT3) was originally identified as one of the genes located within human major histocompatibility complex. It encodes a large proline-rich protein with unknown function. In this study, we found that a fragment of the BAT3 gene product interacts with a candidate tumor suppressor, DAN, in the yeast-based two-hybrid system. We cloned the full-length rat BAT3 cDNA from a fibroblast 3Y1 cDNA library. Our sequence analysis has demonstrated that rat BAT3 cDNA is 3617 nucleotides in length and encodes a full-length BAT3 (1098 amino acids) with an estimated molecular mass of 114,801 daltons, which displays an 87.4% identity with human BAT3. The deletion experiment revealed that the N-terminal region (amino acid residues 1-80) of DAN was required for the interaction with BAT3. Green fluorescent protein-tagged BAT3 was largely localized in the cytoplasm of COS cells. Northern hybridization showed that BAT3 mRNA was expressed in all the adult rat tissues examined but predominantly in testis. In addition, the level of BAT3 mRNA expression was more downregulated in some of the transformed cells, including v-mos- and v-Ha-ras-transformed 3Y1 cells, than in the parental cells.
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SUMMARY A hitherto unrecorded virus having flexible rod‐shaped particles about 740–760 × 13 nm was isolated from Anthoxanthum odoratwn L. It was transmitted by sap inoculation, but not by several species of insect, seed or soil to 18 species of Gramineae including wheat, oats and barley. In susceptible species the virus normally produced a mosaic mottling of the leaves which was sometimes followed by a necrotic streaking or striping.
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The evolutionary origin of vertebrate placodes remains controversial because divergent morphologies in urochordates, cephalochordates and vertebrates make it difficult to recognize organs that are clearly homologous to placode-derived features, including the olfactory organ, adenohypophysis,lens, inner ear, lateral line and cranial ganglia. The larvacean urochordate Oikopleura dioica possesses organs that morphologically resemble the vertebrate olfactory organ and adenohypophysis. We tested the hypothesis that orthologs of these vertebrate placodes exist in a larvacean urochordate by analyzing the developmental expression of larvacean homologs of the placode-marking gene families Eya, Pitx and Six. We conclude that extant chordates inherited olfactory and adenohypophyseal placodes from their last common ancestor, but additional independent proliferation and perhaps loss of placode types probably occurred among the three subphyla of Chordata.
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