An analysis of protocols and publications suggested that most discontinuations of clinical trials were not based on preplanned interim analyses or stopping rules.

OBJECTIVES To investigate the frequency of interim analyses, stopping rules, and data safety and monitoring boards (DSMBs) in protocols of randomized controlled trials (RCTs); to examine these features across different reasons for trial discontinuation; and to identify discrepancies in reporting between protocols and publications. STUDY DESIGN AND SETTING We used data from a cohort of RCT protocols approved between 2000 and 2003 by six research ethics committees in Switzerland, Germany, and Canada. RESULTS Of 894 RCT protocols, 289 prespecified interim analyses (32.3%), 153 stopping rules (17.1%), and 257 DSMBs (28.7%). Overall, 249 of 894 RCTs (27.9%) were prematurely discontinued; mostly due to reasons such as poor recruitment, administrative reasons, or unexpected harm. Forty-six of 249 RCTs (18.4%) were discontinued due to early benefit or futility; of those, 37 (80.4%) were stopped outside a formal interim analysis or stopping rule. Of 515 published RCTs, there were discrepancies between protocols and publications for interim analyses (21.1%), stopping rules (14.4%), and DSMBs (19.6%). CONCLUSION Two-thirds of RCT protocols did not consider interim analyses, stopping rules, or DSMBs. Most RCTs discontinued for early benefit or futility were stopped without a prespecified mechanism. When assessing trial manuscripts, journals should require access to the protocol.

Premature Discontinuation of Randomized Trials in Critical and Emergency Care: A Retrospective Cohort Study.

OBJECTIVES Randomized clinical trials that enroll patients in critical or emergency care (acute care) setting are challenging because of narrow time windows for recruitment and the inability of many patients to provide informed consent. To assess the extent that recruitment challenges lead to randomized clinical trial discontinuation, we compared the discontinuation of acute care and nonacute care randomized clinical trials. DESIGN Retrospective cohort of 894 randomized clinical trials approved by six institutional review boards in Switzerland, Germany, and Canada between 2000 and 2003. SETTING Randomized clinical trials involving patients in an acute or nonacute care setting. SUBJECTS AND INTERVENTIONS We recorded trial characteristics, self-reported trial discontinuation, and self-reported reasons for discontinuation from protocols, corresponding publications, institutional review board files, and a survey of investigators. MEASUREMENTS AND MAIN RESULTS Of 894 randomized clinical trials, 64 (7%) were acute care randomized clinical trials (29 critical care and 35 emergency care). Compared with the 830 nonacute care randomized clinical trials, acute care randomized clinical trials were more frequently discontinued (28 of 64, 44% vs 221 of 830, 27%; p = 0.004). Slow recruitment was the most frequent reason for discontinuation, both in acute care (13 of 64, 20%) and in nonacute care randomized clinical trials (7 of 64, 11%). Logistic regression analyses suggested the acute care setting as an independent risk factor for randomized clinical trial discontinuation specifically as a result of slow recruitment (odds ratio, 4.00; 95% CI, 1.72-9.31) after adjusting for other established risk factors, including nonindustry sponsorship and small sample size. CONCLUSIONS Acute care randomized clinical trials are more vulnerable to premature discontinuation than nonacute care randomized clinical trials and have an approximately four-fold higher risk of discontinuation due to slow recruitment. These results highlight the need for strategies to reliably prevent and resolve slow patient recruitment in randomized clinical trials conducted in the critical and emergency care setting.

Planning and reporting of quality-of-life outcomes in cancer trials.

BACKGROUND Information about the impact of cancer treatments on patients' quality of life (QoL) is of paramount importance to patients and treating oncologists. Cancer trials that do not specify QoL as an outcome or fail to report collected QoL data, omit crucial information for decision making. To estimate the magnitude of these problems, we investigated how frequently QoL outcomes were specified in protocols of cancer trials and subsequently reported. DESIGN Retrospective cohort study of RCT protocols approved by six research ethics committees in Switzerland, Germany, and Canada between 2000 and 2003. We compared protocols to corresponding publications, which were identified through literature searches and investigator surveys. RESULTS Of the 173 cancer trials, 90 (52%) specified QoL outcomes in their protocol, 2 (1%) as primary and 88 (51%) as secondary outcome. Of the 173 trials, 35 (20%) reported QoL outcomes in a corresponding publication (4 modified from the protocol), 18 (10%) were published but failed to report QoL outcomes in the primary or a secondary publication, and 37 (21%) were not published at all. Of the 83 (48%) trials that did not specify QoL outcomes in their protocol, none subsequently reported QoL outcomes. Failure to report pre-specified QoL outcomes was not associated with industry sponsorship (versus non-industry), sample size, and multicentre (versus single centre) status but possibly with trial discontinuation. CONCLUSIONS About half of cancer trials specified QoL outcomes in their protocols. However, only 20% reported any QoL data in associated publications. Highly relevant information for decision making is often unavailable to patients, oncologists, and health policymakers.

Pollen record from Kleiner Mochowsee, Germany

A Holocene pollen diagram from Kleiner Mochowsee (northern Niederlausitz, East Germany) shows pine as an important constituent of the woodland south of the Schwielochsee. Oak woodland was widespread since the Atlantic. Betula lost its importance at the end of the Preboreal. Fagus is represented continuously in the pollen record since the Atlantic, Carpinus since the Subboreal. However, the two latter tree species remain without great importance throughout the whole pollen record. The poor sandy soils are furthermore reflected by the low values of Corylus during the Boreal, comparable to other records from Berlin and its surrounding area. The 'classical' elm decline could be shown for the Niederlausitz, radiocarbon dates assume a contemporaneous age for this event with other records from northern Germany. Only small-scaled human impact is indicated in prehistoric times, during the migration period it seems to have ceased completely. Later, in the Medieval, deforestation and tillage can be shown. Secale was cultivated since the early Medieval; an accompanying weed flora appeared at the same time. Cultivation of Fagopyrum and Linum usitatissimum could be shown for the late Medieval times.

Pollen record and age determination of a sediment profile from Frengstadsetra, Norway

Innerdalen was once a mountain valley (ca. 780 m a.s.l.) with birch forests, bogs and several summer farms. Today it is a 6.5 km**2 artifical lake. In 1980 and 1981 archaeological and palynological investigations were carried out due to the hydroelectric power plans. Radiocarbon dated pollen diagrams from 9 different localities in Innerdalen provide information on a mountain environment which has been exploited to varying degrees by human groups for thousands of years. In the Birch Zone, ca. 9500-8500 years B.P., the deglaciated surface is vegetated by the normal sequence of pioneering species, first show-bed communities, then shrub/dwarf-shrub communities, and finally a birch forest community. In the Pine Zone, ca. 8500-7500 years B.P., the mixed Birch-Pine forest which prevailed at the end of the Birch Zone is replaced by a dense pine forest. The tree limit was higher than it is today. In the Alder Zone, ca. 7500-4000 years B.P., the newly arrived alder gradually succeeded pine, particularily on good soils. This alder forest has a modem analog in the pre-alpine gray alder forests in Norway. In the last part of the Alder Zone, ca. 6000-4000 years B.P., elm and hazel are nominally present on particularily rich soils, marking the edaphic and climatic optimum in Innerdalen. During this time the first evidence of human impact on the vegetation is apparent in the pollen diagrams. At both Sætersetra in the south of the valley and Liabekken in the north, forest clearance and the development of grazed grass meadows is documented, and human impact continues until the present. The Herb Zone, ca. 4000 years B.P. to 1600 A.D., is characterized by the rapid decline of alder. The forest is increasingly open, and bog formation is initiated. The sub-alpine belt of birch forest is established, probably due to the shift to a cooler, moister climate. Human activity can also have influenced the vegetational changes, although at 4 of the localities human activity also is first apparent after the alder decline. Some localities show measurably less human impact on the vegetation ca. 2600-2000 years B.P. Grazing intensity increases ca. 2000 years B.P. At the end of the Herb Zone rye and barley pollen is registered at Sætersetra and Flonan, indicating contact between the grazing activities of Innerdal and grain cultivation activities outside the valley. The Spruce Zone, ca. 1600 A.D. to the present, does not begin synchronously since the presence of long-distance transported spruce pollen at a locality is entirely dependent on the density of the vegetation ie. degree of human impact. The youngest spruce rise is ca. 1500 A.D. at Røstvangen, when summerfarming is initiated. Summerfarming activities in Innerdal produce an increasingly open landscape. Rye and barley pollen at several localities may indicate limited local cultivation, but is more likely long-distance transport via humans and domesticated animals from cultivated areas outside Innerdalen.

Pollen records from Elbe-Weser Dreieck

A long-running interdisciplinary research project on the development of landscape, prehistoric habitation and the history of vegetation within a "siedlungskammer" (limited habitation areal from neolithic to modern times has been carried out in the NW German lowlands, The siedlungskammer Flögeln is situated between the rivers Weser and EIbe and comprises about 23.5 km^2. It is an isolated pleistocene area surrounded by bogs, the soils consisting mainly of poor sands. In this siedlungskammer large-seale archaeological excavations and mappings have been performed, parallel to pedological, historical and above all pollen analytical investigations. The aim of the project is to record the individual phases in time, to delimit the respective settlement areas and to reconstruct the conditions of life and economy for each time period. A dense network of 10 pollen diagrams has been constructed. Several of them derive from the marginal area and from the centre of the large raised bog north of the siedlungskammer. These diagrams reflect the history of vegetation and habitation of a large region; due to the large pollen source area the habitation phases in the diagrams are poorly defined. Even in the utmost marginal diagram of this woodless bog, a great village with adjoining fields, situated only 100 m away from it, is registered with only low values of anthropogenic indicators. In contrast to this, the numerous pollen diagrams from kettle-hole bogs inside the siedlungskammer yield an exact picture of the habitation of the siedlungskammer and their individual parts. Early traces of habitation can be identified in the pollen diagram soon after the elm decline (around 5190 BP). Some time later in the middle neolithic period there follows a marked habitation phase, which starts between 4500 and 4400 BP and reflects the immigration of the trichterbecher culture. It corresponds to the landnam phase of Iversen in Denmark and begins with a sharp decline of the pollen curves of lime and oak, followed by the increase of anthropogenic indicators pointing to arable and pastural farming. High values of wild grasses and Calluna witness extensive forest grazing. This middle to late neolithic habitation is also registered archaeologically by settlements and numerous graves. After low human activity during Bronze Age and Older Iron Age times the archaeological and pollen analytical records of Roman and Migration periods is again very strong. This is followed by a gap in habitation during the 6th and 7th centuries and afterwards in the western part of the siedlungskammer from about 700 AD until the 14th century by the activity of the medieval village of Dalem, that was also excavated and whose fields were recorded by phosphate mapping to a size of 117 hectares. This medieval settlement phase is marked by much cereal cultivation (mainly rye). The dense network of pollen diagrams offers an opportunity to register the dispersion of the anthropogenic indicators from the areas of settlement to different distances and thus to obtain quantitative clues for the assessment of these anthropogenic indicators in pollen diagrams. In fig. 4 the reflection of the neolithic culture in the kettle-hole bogs and the large raised bog is shown in 3 phases: a) pre landnam, b) TRB-landnam, c) post landnam. Among arboreal pollen the reaction of Quercus is sharp close to the settlement but is not found at more distant profiles, whilst in contrast to this Tilia shows a significant decline even far away from the settlements. The record of most anthropogenic indicators outside the habitation area is very low, in particular cereal pollen is poorly dispersed; much more certain as an indicator for habitation (also for arable farming!) is Plantago lanceolata. A strong increase of wild grasses (partly Calluna aswell) some distance from the habitation areas indicates far reaching forest grazing. Fig. 5 illustrates the reflection of the anthropogenie indicators from the medieval village Dalem. In this instance the field area could be mapped exactly using phosphate investigations, and it has been possible to indicate the precise distances of the profile sites from the medieval fields. Here also, there is a clear correlation between decreasing anthropogenic indicators and increasing distance. In a kettle-hole bog (FLH) a distance of 3000 m away this marked settlement phase is not registered. The contrast between the pollen diagrams SWK and FLH (fig. 2 + 3, enclosure), illustrates the strong differences between diagrams from kettlehole bogs close to and distant from the settlements, for the neolithic as well as for the medieval period. On the basis of the examples presented here, implications concerning the interpretation of pollen diagrams with respect to habitation phases are discussed.

Estudio de la ecología de Ulmus laevis Pallas en la Península Ibérica

Esta tesis doctoral pretende profundizar en el conocimiento de la ecología de Ulmus laevis Pallas, especie autóctona en peligro de extinción en la Península Ibérica, con el fin de proponer medidas adecuadas para su conservación. Se ha estudiado la distribución natural de la especie atendiendo a aspectos edáficos. Los resultados muestran que U. laevis presenta menor capacidad de acidificación de la rizosfera, menor actividad de la reductasa férrica y menor homeostasis que U. minor Mill. cuando crecen en sustratos con una disponibilidad de hierro limitada. Estas diferencias ayudan a comprender la distribución de ambas especies en la Península Ibérica: U. laevis se ve restringido a suelos ácidos o moderadamente ácidos, mientras que U. minor es capaz de habitar tanto suelos ácidos como básicos. Se han analizado las propiedades hidráulicas y anatómicas de U. laevis, constatando que sus características son favorables en ambientes con gran disponibilidad hídrica y que se trata del olmo ibérico más vulnerable a la cavitación por estrés hídrico, por lo que la aridificación del clima y la pérdida de los freáticos supone un riesgo para sus poblaciones. Para evaluar la capacidad de recuperación de la especie se han estudiado la diversidad y estructura genética espacial de las dos mayores poblaciones españolas. Los resultados evidencian que estas poblaciones mantienen niveles de diversidad equiparables o ligeramente superiores a los europeos, pese a haber sufrido un cuello de botella prolongado durante las glaciaciones y a las reducciones poblacionales recientes. En la actualidad la endogamia no representa un riesgo para estas poblaciones. También se ha analizado la producción, dispersión y predación de semillas en Valdelatas (Madrid). Los resultados han mostrado que el viento dispersa las sámaras a corta distancia (<30 m) y que los años no veceros las probabilidades de establecimiento de regenerado son bajas. Además, la producción de sámaras vanas puede tratarse de un carácter adaptativo que aumenta la eficiencia biológica de la especie, ya que favorece la supervivencia de las semillas embrionadas disminuyendo sus tasas de predación pre- y post-dispersión. La modificación del hábitat de esta especie como consecuencia de las actividades humanas afecta de manera negativa al establecimiento del regenerado. La conservación de esta especie a largo plazo requiere la recuperación de los niveles freáticos y de regímenes hidrológicos que permitan avenidas, ya que estas crean las condiciones adecuadas para el establecimiento de regenerado al eliminar la vegetación preexistente y depositar barro. ABSTRACT Ulmus laevis Pallas is an endangered species in the Iberian Peninsula. Therefore, in order to be able to propose adequate management guidelines for its conservation, this PhD Thesis intends to advance the knowledge on the species ecology in the region. Firstly, the species natural distribution was studied in relation to soil nature. Results show that U. minor Mill. had a higher root ferric reductase activity and proton extrusion capability than U. laevis, and maintained a better nutrient homeostasis when grown under iron limiting conditions. These differences in root Fe acquisition efficiencies proved helpful to understand the distribution of these species in the Iberian Peninsula, where U. laevis is restricted to acid or moderately acid soils, whereas U. minor can grow both in acid and basic soils. Secondly, we studied Ulmus laevis’ xylem anatomy and hydraulic traits. These proved favourable for growing under high water availability, but highly susceptible to drought-stress cavitation. Therefore, this species is vulnerable to the Iberian Peninsula’s aridification. Spatial genetic structure and diversity were evaluated in two of the biggest U. laevis populations in Spain in order to evaluate their recovery capabilities. These populations maintain similar or slightly higher diversity levels than European populations, despite having undergone an ancestral genetic bottleneck and having suffered recent population size reductions. No inbreeding problems have been detected in these populations. Seed production, dispersal and predation were assessed in Valdelatas’ elm grove (Madrid). Despite U. laevis samaras being winged nuts, wind dispersed them short distances from the mother tree (<30 m). The seed shadow models show that non-mast years provide very few chances for the stand to regenerate due to their low full seed flux. Empty samaras deceive pre- and post-dispersal predators increasing full seed survival probabilities. Therefore, empty fruit production might be an adaptive trait that increases plant fitness. Finally, human-induced changes in water-table levels and river regulation may affect U. laevis seed dispersal and regeneration establishment negatively. The long-term conservation and expansion of this species in the Iberian Peninsula requires the recovery of water-tables and of natural hydrological regimes, as flooding eliminates vegetation, creating open microhabitats and deposits mud, creating the ideal conditions for seedling establishment.

Ulmus laevis in the Iberian Peninsula: a review of its ecology and conservation

European white elm (Ulmus laevis Pallas) populations are scarce, small and fragmented in the Iberian Peninsula. Due to these characteristics the indigenous status of the species in the region has been questioned, whilst the species? role in Iberian riparian forest ecology has been neglected. Herein we review past studies regarding this species? distribution and ecology in the Iberian Peninsula, with special emphasis on the establishment of conservation priorities. We first present a collection of palaeogeographic, historic and genetic data suggesting that the Iberian Peninsula was a glacial refuge for U. laevis. Secondly, we analyse U. laevis distribution in relation to soil physico- chemical properties and water availability in Spain. Following this, we focus on the reproductive biology of the species, and investigate the effect of masting and empty seed production on predation and regeneration establishment. Finally, based on this knowledge, we propose conservation policies for U. laevis in the Iberian Peninsula.

Evaluación de Ulmus pumila L. y Populus spp. como cultivos energéticos en corta rotación

El presente trabajo estudia el empleo del olmo de Siberia (Ulmus Pumila L.) y el chopo (Populus spp.) en corta rotación y alta densidad para la producción de biomasa con fines energéticos. En el área mediterránea las disponibilidades hídricas son limitadas, por lo que la mayoría de los cultivos energéticos utilizados hasta el momento requieren el aporte de agua de riego; por ello resulta fundamental encontrar especies con bajos requerimientos hídricos, analizar la eficiencia en el uso del agua de diferentes materiales genéticos y optimizar la dosis de riego. Las parcelas experimentales se ubicaron en la provincia de Soria. En el ensayo llevado a cabo con olmo de Siberia se ha analizado el efecto en la producción de la disponibilidad de agua mediante el establecimiento de parcelas en secano y con dos dosis de riego (2000 m3 ha-1 año-1 y 4000 m3 ha-1 año-1 aproximadamente); además, al ser una especie poco estudiada hasta el momento, se ha estudiado también el efecto que tiene sobre el rendimiento la densidad de plantación (3.333 plantas ha-1 y 6.666 plantas ha-1), el tipo de suelo (2 calidades diferentes) y el turno de corta (3 y 4 años). En el caso del chopo, se han evaluado cuatro clones (AF-2, I-214, Monviso y Pegaso) establecidos con una densidad de 20.000 plantas por hectárea. Durante el primer ciclo de tres años se aportó el mismo volumen de riego a todas las parcelas, mientras que durante el segundo ciclo se establecieron 8 regímenes hídricos diferentes. Por otra parte, se ha investigado sobre el uso del potencial hídrico de las plantas para evaluar el estrés hídrico de las mismas y se ha estimado la producción de biomasa foliar y el Índice de Área Foliar (LAI) de ambas especies, relacionando los valores obtenidos con la dosis de riego y la producción de biomasa. Los resultados muestran que los suelos inundados reducen la tasa de supervivencia de los olmos durante el periodo de implantación, sin embargo la mortalidad durante los siguientes periodos vegetativos es baja y muestra buena capacidad de rebrote. La productividad (kg ha-1 año-1) obtenida fue mayor con un turno de corta de cuatro años que con turno de tres años. El área basal y la altura fueron variables eficaces para predecir la producción de biomasa del olmo de Siberia, obteniendo una variabilidad explicada de más del 80%. En cuanto a los parámetros que mayor influencia tuvieron sobre el crecimiento, el tipo de suelo resulto ser el más relevante, obteniéndose en un suelo agrícola considerado de buena calidad una producción en condiciones de secano de unos 8.000 kg ha-1 año-1. En condiciones de regadío el rendimiento del olmo de Siberia fue al menos el doble que en secano, pero la diferencia entre las dos dosis de riego estudiadas fue pequeña. La producción de biomasa fue mayor en la densidad de plantación más alta (6.666 plantas ha–1) en las parcelas de regadío, sin embargo no se encontraron diferencias significativas entre las dos densidades en secano. El clon de chopo que presentó un mayor rendimiento durante el primer ciclo fue AF-2, alcanzando los 14.000 kg ha-1 año-1, sin embargo la producción de este clon bajó sustancialmente durante el segundo ciclo debido a su mala capacidad de rebrote, pasando a ser I-214 el clon más productivo llegando también a los 14.000 kg ha-1 año-1. Un aporte adicional de agua proporcionó un incremento de la biomasa recogida, pero a partir de unos 6.500 m3 ha-1 año-1 de agua la producción se mantiene constante. El potencial hídrico foliar ha resultado ser una herramienta útil para conocer el estrés hídrico de las plantas. Los olmos de regadío apenas sufrieron estrés hídrico, mientras que los implantados en condiciones de secano padecieron un acusado estrés durante buena parte del periodo vegetativo, que se acentuó en la parte final del mismo. Los chopos regados con las dosis más altas no sufrieron estrés hídrico o fue muy pequeño, en las dosis intermedias sufrieron un estrés moderado ocasionalmente y únicamente en las dosis más bajas sufrieron puntualmente un estrés severo. El LAI aumenta con la edad de los brotes y oscila entre 2 y 4 m2 m−2 en los chopos y entre 2 y 7 m2 m−2 en los olmos. Se encontró una buena relación entre este índice y la producción de biomasa del olmo de Siberia. En general, puede decirse que el olmo de Siberia podría ser una buena alternativa para producir biomasa leñosa en condiciones de secano, mientras que el chopo podría emplearse en regadío siempre que se haga una buena elección del clon y de la dosis de riego. ABSTRACT This work explores the possibilities of biomass production, for energy purposes, of Siberian elm (Ulmus Pumila L.) and poplar (Populus spp.) in Spain. Irrigation is required for the viable cultivation of many energy crops in Mediterranean areas because of low water availability, for this reason species with low water requirements should be a good alternative for biomass production. Moreover, the optimal amount of irrigation water and the performance of the different genetic material in terms of production and water use efficiency should be studied in order to use water wisely. The experimental plots were established in the province of Soria in Spain. Given the small amount of information available about Siberian elm, besides studying the influence of water availability (rain-fed and two different irrigation doses) on biomass production, two different plantation densities (3,333 plants ha-1 and 6,666 plants ha-1), two different soil type and two cutting cycles (three years and four years) were assessed. In the case of poplar, four clones belonging to different hybrids (I-214, AF2, Pegaso, and Monviso) were included in a high density plantation (20,000 plants ha-1). During the first cycle, the water supplied in all plots was the same, while 8 different watering regimes were used during the second cycle. The suitability of the use of the leaf water potential to assess the water stress situations has also been investigated. Moreover, leaf biomass production and leaf area index (LAI) were estimated in both species in order to analyze the relationship between these parameters, irrigation dose and biomass production. The results shows that flooded soils have an adverse effect on elm survival in the implantation period, but the percentage of mortality is very low during the following vegetative periods and it shows a good ability of regrowth. The annual yield from a four-year cutting cycle was significantly greater than that from the three-year cutting cycle. Basal diameter and height are effective variables for predicting the production of total biomass; equations with R squared higher than 80% were obtained. The analysis of parameters having an influence on elm growth shows that soil type is the most important factor to obtain a good yield. In soils with enough nutrients and higher waterholding capacity, biomass productions of 8,000 kg ha-1 yr-1 were achieved even under rain-fed conditions. In irrigated plots, Siberian elm production was double than the production of biomass under rain-fed conditions; however, small differences were obtained between the 2 different irrigation doses under study. Biomass yield was greater for the highest planting density (6,666 plants ha–1) in irrigated plots, but significant differences were not found between the 2 densities in rain-fed plots. The clone AF-2 showed the highest production (14,000 kg ha-1 yr-1) during the first cycle, however during the second cycle its growth was lower because of a high mortality rate after regrowth and I-214 achieves the greatest production (14,000 kg ha-1 yr-1). An additional water supply provided a greater amount of biomass, but over about 6500 m3 ha-1 yr-1 of water the production is constant. Leaf water potential has been shown to be a useful tool for finding out plant water status. Irrigated elms hardly suffered water stress, while rain-fed elms suffered a pronounced water stress, which was more marked at the end of the vegetative period. Most of poplars did not show water stress; leaf water potentials only showed an important water stress in the plots irrigated with the lowest doses. LAI increases with shoot age and it ranges from 2 to 4 m2 m−2 in poplars and from 2 to 7 m2 m−2 in elms. A good relationship has been found between this index and Siberian elm production. In general, Siberian elm could be a good alternative to produce woody biomass in rainfed plots, while poplar could be used in irrigated plots if a suitable clone and irrigation dose are chosen.

Purification and Characterization of a Low-Molecular-Weight Phospholipase A2 from Developing Seeds of Elm1

Phospholipase A2 (PLA2) was purified about 180,000 times compared with the starting soluble-protein extract from developing elm (Ulmus glabra) seeds. On sodium dodecyl sulfate-polyacrylamide gel electrophoresis the purified fraction showed a single protein band with a mobility that corresponded to 15 kD, from which activity could be recovered. When analyzed by matrix-assisted laser-desorption ionization-time-of-flight mass spectrometry, the enzyme had a deduced mass of 13,900 D. A 53-amino acid-long N-terminal sequence was determined and aligned with other sequences, giving 62% identity to the deduced amino acid sequence of some rice (Oryza sativa) expressed sequence tag clones. The purified enzyme had an alkaline pH optimum and required Ca2+ for activity. It was unusually stable with regard to heat, acidity, and organic solvents but was sensitive to disulfide bond-reducing agents. The enzyme is a true PLA2, neither hydrolyzing the sn-1 position of phosphatidylcholine nor having any activity toward lysophosphatidylcholine or diacylglycerol. The biochemical data and amino acid sequence alignments indicate that the enzyme is related to the well-characterized family of animal secretory PLA2s and, to our knowledge, is the first plant enzyme of this type to be described.