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This (two-season) study was undertaken to assess the involvement of gibberellins (GAs), cytokinins (CKs), and auxins (AX) in dormancy of the sweet cherry buds ‘Summit’. Our hypothesis consisted in the assumption that representatives of these hormone groups are able to mark the transition between different dormancy phases. Changes in the transition between endo- and ecodormancy and the stages of ontogenetic development were not recognizable by bioactive GA1, GA5, GA7. The transient increase of GA3 during ecodormancy might be interpreted as an indication of the preservation of ecodormancy. The content of the biological active bases tZ, cZ, and DHZ was equal between endo- and ecodormancy. However, the content increased significantly in the first phase of ontogenetic development. The summation of the representatives of the various CKs (total iP-type, total tZ-type, total CK bases, total CK ribosides, total CK nucleotides, total O-glucosides, total N-glucosides, and total CKs) showed no differences regarding their levels during endo- and ecodormancy. These values increased markedly in the subsequent phase. AX increased after ecodormancy. By contrast, from side green until open cluster no differences occurred. As shown for AX, the content of oxIAA increased after ecodormancy. The content of IAAsp was low during endodormancy and increased transiently during ecodormancy and early ontogenetic development. This study revealed that no changes in the content of different bioactive GAs (exception GA3), CKs, and AX occurred during winter rest, and more precisely, during endo- and ecodormancy. These metabolites, therefore, are not suitable to differentiate between these dormancy phases. The ontogenesis is accompanied by specific changes in the content of bioactive molecules, precursors, and conjugation products.

High-entropy alloys are extensively studied due to their very promising properties. However manufacturing methods currently used to prepare HEAs are complicated, costly, and likely non-industrially scalable processes. This limits their evolution and poses questions regarding the material's applicability in the future. Considering the abovementioned point, we developed a novel methodology for efficient HEA production using a low ball-to-powder ratio (BPR). Using different milling times, we manufactured four HEA powder precursors using a BPR of 5:1, which were later sintered via the Spark Plasma Sintering technique and heat treated. Microstructural characterization was performed by optical microscopy, Scanning Electron Microscopy equipped with EDS and EBSD detectors, and X-ray diffraction. Mechanical properties were measured using nano and microhardness techniques. In this work, we follow the structural evolution of the material and connect it with the strengthening effect as a function of milling time. Furthermore, we discuss the impact of different sintering and annealing conditions, proving that HEAs characterized by high mechanical properties may be manufactured using low BPR.

Eine direkte Auswirkung des rezenten Klimawandels auf die Vegetation ist die Verfrühung phänologischer Stadien, besonders im Frühjahr (WALDAU & CHMIELEWSKI, 2018; CHMIELEWSKI et al., 2004; WOLFE et al., 2005). Diese Trends wurden weltweit beobachtet und sind hauptsächlich auf den Anstieg der Lufttemperatur zurückzuführen, was den engen Zusammenhang zwischen Pflanzenentwicklung und Temperatur belegt. Dieser stetige Temperaturanstieg wird sich in Zukunft fortsetzen und zu zeitlichen und räumlichen Verschiebungen in der Vegetationsentwicklung führen. Um diese Veränderungen abschätzen zu können, sind plausible phänologische Modelle erforderlich, wobei das Kältebedürfnis, das für die Überwindung der Dormanz erforderlich ist, hierbei eine der Schlüsselgrößen ist. Ziel dieser Studie war es die zukünftigen Auswirkungen des Klimawandels auf die natürliche Vegetation in Deutschland abzuschätzen. In einer dreijährigen Studie (Winter 2015/16 – 2017/18) wurde der Zeitpunkt der Dormanzbrechung für verschiedene Baumarten experimentell in Klimakammerversuchen bestimmt. Im Rahmen dieses Vortrages sollen die Ergebnisse für die Schwarzerle (Alnus glutinosa) dargestellt werden. Nach der Ermittlung des für den Blattaustrieb der Schwarzerle notwendigen Kältereizes wurde ein Chilling/Forcing Modell parametrisiert und anschließend an den phänologischen Beobachtungdaten des Deutschen Wetterdienstes (1951-2015) validiert. Für die Abschätzung der künftigen klimatischen Entwicklung wurde ein Klimaensemble aus sieben verschieden Klimamodellrechnungen für zwei Klimaszenarien (RCP 2.6 & 8.5) verwendet. Für den Zeitraum 2010-2100 werden neben den zeitlichen Trends der Lufttemperatur und der Phänologie zusätzlich die regionalen Unterschiede in Deutschland (Nord-Ost/Nord-West/Süd-Ost/Süd-West) aufgezeigt. Literatur: CHMIELEWSKI, F. M., MÜLLER, A. & BRUNS, E. (2004): Climate changes and trends in phenology of fruit trees and field crops in Germany, 1961–2000. Agricultural and Forest Meteorology 121 (1), 69-DOI: https://doi.org/10.1016/S0168-1923(03)00161-8. WALDAU, T. & CHMIELEWSKI, F. M. (2018): Spatial and temporal changes of spring temperature, thermal growing season and spring phenology in Germany 1951–2015. Meteorol. Z. 27 (4), 335-342.DOI: https://doi.org/10.1127/metz/2018/0923. WOLFE, D. W., SCHWARTZ, M. D., LAKSO, A. N., OTSUKI, Y., POOL, R. M. & SHAULIS, N. J. (2005): Climate change and shifts in spring phenology of three horticultural woody perennials in northeastern USA. International Journal of Biometeorology 49 (5), 303-309. DOI: https://doi.org/10.1007/s00484-004-0248-9.

Commonly used S235JR structural steel, generally associated with good weldability, was joined by high-speed friction welding (HSFW). The friction welding tests were performed with a rotational speed of n = 8000 rpm and four different values of the unit pressure in the friction phase (pf) in the range of 64–255 MPa. The obtained joints were subjected to metallographic observations using an optical microscope; in selected zones of friction joints the average grain size was specified in accordance with the EN ISO 643:2012 standard; the hardness of friction joints was measured using the Vickers method. The friction-welded joint with the highest pf was EBSD-investigated. The obtained friction-welded joints resembled an hourglass, and the microstructure of individual zones of the joints differed depending on the height (axis, radius) of the observations. The generated joining conditions resulted in a significant refinement of the microstructure in the friction weld—the average grain size is about 1 µm2 (for base material it was 21 µm2). The highest increase in hardness above 340 HV0.1 was recorded in the friction weld of the welded joint with the lowest used value pressure in the friction phase. Such a sharp increase in hardness can make the resulting friction-welded joint become sensitive to dynamic or fatigue loads. The electron backscatter diffraction (EBSD) investigation confirmed the strong refinement of the microstructure in the friction-welded joint and the occurrence of the phenomenon of dynamic recrystallization (DRX). The friction weld was also characterized by a large share of high-angle boundaries (HAGBs) >80%. These results may indicate that during high-speed friction welding it is possible to create conditions like those obtained during the High-Pressure Torsion (the method used to produce UFG materials) process.

The surfaces of engineering materials play key roles in interactions with the environment and very often influence durability under external conditions [...]

The paper presents the result of an analysis of applicability of various electromagnetic methods of nondestructive evaluation for creep damage detection in a novel heat resistant steel - T24 grade. Two sample sets, cut out from membrane wall tubes, were investigated – the as-delivered one and another exploited for 36,000 h in a power plant. There are described results of magnetic hysteresis loops B(H), Barkhausen noise (BN) and magnetoacoustic emission (MAE) signals measurements. Changes of the B(H) loops shape are observed mainly in the “knee” regions. The BN signal is practically unaffected by exploitation. The most strongly changing signal is the MAE signal, yet the change is not very easy to quantify as it concerns signal envelopes shape not overall intensity. The paper describes various possible signal parameters that can be used. The best one seems to be the ratio of the total pulse count for a quarter of magnetisation (demagnetisation) to the one for the magnetisation half-period. The important issue is in that case a proper choice of the threshold level in order to obtain good sensitivity to creep damage level and reasonably low stochastic pulse count scatter.

Models used to predict the onset of fruit tree blossom under changed climate conditions should be physiologically based as much as possible. Pure optimized phenology models carry the risk of unrealistic predictions due to a misinterpretation of metabolic processes. This was the motivation determining the relevant phases for chill and heat accumulation, which induces cherry blossom (cv. Summit). Investigations are based on 8 years of observational and analytical data, as well as on controlled experiments. For ‘Summit’ buds, to be released from endodormancy, 43 chill portions from 1 September are necessary. After endodormancy release (t1), on average on 30 November, no further chilling is required, because no correlation between chill accumulation during ecodormancy and the subsequent heat accumulation until ‘Summit’ blossom exist. The declining amount of heat, which induces cherry blossom after t1—shown in several forcing experiments—seems to be the result of the declining bud’s abscisic acid (ABA) content, up to ~50% until the beginning of ontogenetic development. Shortly after t1, when the bud’s ABA content is high, a huge amount of heat is necessary to induce cherry blossom under controlled conditions. Heat requirement reduces during ecodormancy along with the reduction in the ABA content. According to these findings, plant development during ecodormancy is suppressed by low temperatures in the orchard and a slowly declining bud’s ABA content. These results should lead to a better consideration of the ecodormancy phase in phenology models.

International audience; Spring phenology of temperate trees has advanced worldwide in response to global warming. However, increasing temperatures may not necessarily lead to further phenological advance, especially in the warmer latitudes because of insufficient chilling and/or shorter daylength. Determining the start of the forcing phase, i.e. when buds are able to respond to warmer temperatures in spring, is therefore crucial to predict how phenology will change in the future. In this study, we used 4,056 leaf-out date observations during the period 1969-2017 for clones of European beech (Fagus sylvatica L.) and pedunculate oak (Quercus robur L.) planted in 63 sites covering a large latitudinal gradient (from Portugal ~ 41°N to Norway ~ 63°N) at the International Phenological Gardens in order to (i) evaluate how the sensitivity periods to forcing and chilling have changed with climate warming, and (ii) test whether consistent patterns occur along biogeographical gradients, i.e. from colder to warmer environments. Partial Least Squares regressions suggest that the length of the forcing period has been extended over the recent decades with climate warming in the colder latitudes but has been shortened in the warmer latitudes for both species, with a more pronounced shift for beech. We attribute the lengthening of the forcing period in the colder latitudes to earlier opportunities with temperatures that can promote bud development. In contrast, at warmer or oceanic climates, the beginning of the forcing period has been delayed, possibly due to insufficient chilling. However, in spite of a later beginning of the forcing period, spring phenology has continued to advance at these areas due to a faster satisfaction of heat requirements induced by climate warming. Overall, our results support that ongoing climate warming will have different effects on the spring phenology of forest trees across latitudes due to the interactions between chilling and forcing requirements and photoperiod.

Winter dormancy is still a “black box” in phenological models, because it evades simple observation. This study presents the first step in the identification of suitable metabolites which could indicate the timing and length of dormancy phases for the sweet cherry cultivar ‘Summit’. Global metabolite profiling detected 445 named metabolites in flower buds, which can be assigned to different substance groups such as amino acids, carbohydrates, phytohormones, lipids, nucleotides, peptides and some secondary metabolites. During the phases of endo- and ecodormancy, the energy metabolism in the form of glycolysis and the tricarboxylic acid (TCA) cycle was shut down to a minimum. However, the beginning of ontogenetic development was closely related to the up-regulation of the carbohydrate metabolism and thus to the generation of energy for the growth and development of the sweet cherry buds. From the 445 metabolites found in cherry buds, seven were selected which could be suitable markers for the ecodormancy phase, whose duration is limited by the date of endodormancy release (t1) and the beginning of ontogenetic development (t1*). With the exception of abscisic acid (ABA), which has been proven to control bud dormancy, all of these metabolites show nearly constant intensity during this phase.

Climate change has a strong impact on vegetation dynamics and the relationship between temperature changes and shifts in plant development is well known. However, temperature does not change homogeneously and high spatial and temporal variabilities are possible. For a 65-year period from 1951–2015, we examined trends of mean air temperatures and bioclimatic parameters such as the onset of thermal growing season and two relevant phenological stages in Germany. We focused our analysis only on statistical significant trends. In order to compare them for the same spatial and temporal resolution, gridded datasets were used. From 1951–2015 spring air temperature (March-May) increased by 1.9 K. In the same time the average onset of thermal growing season started 20 days earlier and the beginning of cherry flowering and leaf unfolding of silver birch was advanced by 11 and 13 days, respectively. Nevertheless, a high spatial variability of trends was detected for all parameters. Strongest shifts were more pronounced in coastal areas of Germany and the regional investigation showed significantly stronger trends for North Germany than for South Germany. The study confirmed a strong synchronisation of the temporal and spatial changes in air temperature and the investigated bioclimatic parameters.

In this work, the effect of ion implantation and Cr content on structural properties of ODS steel have been investigated. Structural properties were measured by using Grazing Incidence X-ray Diffraction (GIXRD) and Small Angle Neutron Scattering (SANS) techniques. Mechanical properties, in the function of Cr addition were measured by means of nanoindentation technique. It has been found that bands characteristic for (100), (200) or (211) crystallographic planes, upon impact of ions change their position (shift towards lower 2θ). Implementation of Small-Angle Neutron Scattering (SANS) technique has help to estimate particle characteristics in ODS specimens. Finally, mechanical results clearly show impact of Cr addition on the hardness and Young modulus of the manufactured specimens.

One of the most important challenges faced while producing elements of a thermoelectric module (TEM) is the development of an appropriate joining technology affecting the performance of the whole thermoelectric generator. The produced joints must be characterized not only by high electrical conductivity, high heat conductivity and good adhesion, but also proper mechanical strength and, due to the working conditions, good chemical and temperature stability. This work presents lead-free junctions between a skutterudite material (CoSb3) and a metallic electrode for middle-temperature range applications. The production process and the properties of the obtained junctions are described. The materials were joined by the resistance soldering technique using the Spark Plasma Sintering (SPS) apparatus. The properties of the samples, including their electrical conductivity and Seebeck coefficient were determined and presented. Scanning electron microscopy (SEM) was used to investigate the microstructure, whereas electron dispersive spectroscopy (EDS) was employed to analyze the distribution of the elements. The research was aimed at examining the progress of diffusion between the bounded surfaces. The obtained junction was characterized by a very low resistivity. This work summarizes the properties of the produced junctions and the possibility of their application.

Spring frost can be a limiting factor in sweet cherry (Prunus avium L.) production. Rising temperatures in spring force the development of buds, whereby their vulnerability to freezing temperatures continuously increases. With the beginning of blossom, flowers can resist only light frosts without any significant damage. In this study, we investigated the risk of spring frost damages during cherry blossom for historical and future climate conditions at two different sites in NE (Berlin) and SW Germany (Geisenheim). Two phenological models, developed on the basis of phenological observations at the experimental sweet cherry orchard in Berlin-Dahlem and validated for endodormancy release and for warmer climate conditions (already published), were used to calculate the beginning of cherry blossom in Geisenheim, 1951-2015 (external model validation). Afterwards, on the basis of a statistical regionalisation model WETTREG (RCP 8.5), the frequency of frost during cherry blossom was calculated at both sites for historical (1971-2000) and future climate conditions (2011-2100). From these data, we derived the final flower damage, defined as the percentage of frozen flowers due to single or multiple frost events during blossom. The results showed that rising temperatures in this century can premature the beginning of cherry blossom up to 17 days at both sites, independent of the used phenological model. The frequency and strength of frost was characterised by a high temporal and local variability. For both sites, no significant increase in frost frequency and frost damage during blossom was found. In Geisenheim, frost damages significantly decreased from the middle of the twenty-first century. This study additionally emphasises the importance of reliable phenological models which not only work for current but also for changed climate conditions and at different sites. The date of endodormancy release should always be a known parameter in chilling/forcing models.

Six phenological models, two simple forcing (F)-models and one sequential chilling/forcing (CF)-model, each with and without day length (DL)-term in the forcing approach were optimised (2001–2010) and validated (2011–2015) on very accurate blossoming data of an experimental sweet cherry orchard at Berlin-Dahlem (cultivar ‘Summit’). In parallel, in 3 seasons (2011/2012–2013/2014) climate chamber experiments were performed in order to determine the end of dormancy for ‘Summit’, which is usually an unknown or uncertain parameter in phenological modelling. Additionally, in the season 2013/2014 an in situ climate change experiment on three trees in the sweet cherry orchard were arranged, which was used to validate the phenological models for distinctly warmer climate conditions at the experimental site. On the basis of our climate chamber experiments we quantified the chilling requirement of ‘Summit’ trees. Thus, we were able to identify a CF-model for the beginning of sweet cherry blossom which is mostly physiologically based and works well for current and for future climate conditions at the experimental site. This paper also shows how phenological models can fail under warmer climates, if either the model is too simple or the model parameters are wrong. Additional, we confirmed that phenological models with DL-term in the forcing approach clearly surpassed the conventional phenological models without this parameter. The reason for this behaviour is extensively discussed.

International audience; AbstractGrain legumes produce high-quality protein for food and feed, and potentially contribute to sustainable cropping systems, but they are grown on only 1.5% of European arable land. Low temporal yield stability is one of the reasons held responsible for the low proportion of grain legumes, without sufficient quantitative evidence. The objective of this study was to compare the yield stability of grain legumes with other crop species in a northern European context and accounting for the effects of scale in the analysis and the data. To avoid aggregation biases in the yield data, we used data from long-term field experiments. The experiments included grain legumes (lupin, field pea, and faba bean), other broad-leaved crops, spring, and winter cereals. Experiments were conducted in the UK, Sweden, and Germany. To compare yield stability between grain legumes and other crops, we used a scale-adjusted yield stability indicator that accounts for the yield differences between crops following Taylor’s Power Law. Here, we show that temporal yield instability of grain legumes (30%) was higher than that of autumn-sown cereals (19%), but lower than that of other spring-sown broad-leaved crops (35%), and only slightly greater than spring-sown cereals (27%). With the scale-adjusted yield stability indicator, we estimated 21% higher yield stability for grain legumes compared to a standard stability measure. These novel findings demonstrate that grain legume yields are as reliable as those of other spring-sown crops in major production systems of northern Europe, which could influence the current negative perception on grain legume cultivation. Initiatives are still needed to improve the crops agronomy to provide higher and more stable yields in future.

Trees control the flowering processes in response to both environmental and endogenous (mechanisms at cellular/tissue level) conditions. Dormancy of flower buds is characterized by the reduction of growth and the enhancement of frost and desiccation resistance. The release of endodormancy and the beginning of ontogenetic development, as two important dates for developing reliable phenological models, escape from any visible signs. Thus, we identified - to our knowledge as first - relevant proteins in sweet cherry buds occurring during these phenological phases at high time resolution in three seasons (2012/13–2014/15) under natural conditions in Northeast Germany. The protein content of buds from the first week of October to leaf fall, from leaf fall to the end of endodormancy (t1), from t1 to the beginning of ontogenetic development (t1*), and from t1* until swollen bud, was comparable in each of the seasons. The increase of the protein content began after swollen bud and markedly differences occurred at side green, green tip, tight and open cluster. SDS gel electrophoresis followed by peptide mass fingerprinting accomplished by MALDI-TOF MS was applied for protein identification. ‘Volume intensity’ has been used to demonstrate the pattern and changes of proteins. None of the analysed proteins like for cell proliferation/differentiation (Phytosulfokines 3), carbon fixation (Rubisco), and defense against pathogenes (Major allergen Pru sv 1) indicates the date of endodormancy release or the beginning of the (invisible) ontogenetic development. The stages around green tip, tight, and open cluster resulted in markedly increase of the volume intensity of the protein for cell proliferation/differentiation and the carbon fixation, whereas the volume intensity of a protein for defense against pathogens markedly decreased. The pattern and changes of the volume intensity of neoxanthin synthase (NXS) in sweet cherry buds followed the increasing demand during endo- and ecodormancy to produce neoxanthin, which is a prominent member of the group of reactive oxygen species (ROS) scavengers.

Many biochemical processes are involved in regulating the consecutive transition of different phases of dormancy in sweet cherry buds. An evaluation based on a metabolic approach has, as yet, only been partly addressed. The aim of this work, therefore, was to determine which plant metabolites could serve as biomarkers for the different transitions in sweet cherry buds. The focus here was on those metabolites involved in oxidation-reduction processes during bud dormancy, as determined by targeted and untargeted mass spectrometry-based methods. The metabolites addressed included phenolic compounds, ascorbate/dehydroascorbate, reducing sugars, carotenoids and chlorophylls. The results demonstrate that the content of phenolic compounds decrease until the end of endodormancy. After a long period of constancy until the end of ecodormancy, a final phase of further decrease followed up to the phenophase open cluster. The main phenolic compounds were caffeoylquinic acids, coumaroylquinic acids and catechins, as well as quercetin and kaempferol derivatives. The data also support the protective role of ascorbate and glutathione in the para- and endodormancy phases. Consistent trends in the content of reducing sugars can be elucidated for the different phenophases of dormancy, too. The untargeted approach with principle component analysis (PCA) clearly differentiates the different timings of dormancy giving further valuable information. Deutsche Forschungsgemeinschaft (DFG)

Many biochemical processes are involved in regulating the consecutive transition of different phases of dormancy in sweet cherry buds. An evaluation based on a metabolic approach has, as yet, only been partly addressed. The aim of this work, therefore, was to determine which plant metabolites could serve as biomarkers for the different transitions in sweet cherry buds. The focus here was on those metabolites involved in oxidation-reduction processes during bud dormancy, as determined by targeted and untargeted mass spectrometry-based methods. The metabolites addressed included phenolic compounds, ascorbate/dehydroascorbate, reducing sugars, carotenoids and chlorophylls. The results demonstrate that the content of phenolic compounds decrease until the end of endodormancy. After a long period of constancy until the end of ecodormancy, a final phase of further decrease followed up to the phenophase open cluster. The main phenolic compounds were caffeoylquinic acids, coumaroylquinic acids and catechins, as well as quercetin and kaempferol derivatives. The data also support the protective role of ascorbate and glutathione in the para- and endodormancy phases. Consistent trends in the content of reducing sugars can be elucidated for the different phenophases of dormancy, too. The untargeted approach with principle component analysis (PCA) clearly differentiates the different timings of dormancy giving further valuable information.

Many biochemical processes are involved in regulating the consecutive transition of different phases of dormancy in sweet cherry buds. An evaluation based on a metabolic approach has, as yet, only been partly addressed. The aim of this work, therefore, was to determine which plant metabolites could serve as biomarkers for the different transitions in sweet cherry buds. The focus here was on those metabolites involved in oxidation-reduction processes during bud dormancy, as determined by targeted and untargeted mass spectrometry-based methods. The metabolites addressed included phenolic compounds, ascorbate/dehydroascorbate, reducing sugars, carotenoids and chlorophylls. The results demonstrate that the content of phenolic compounds decrease until the end of endodormancy. After a long period of constancy until the end of ecodormancy, a final phase of further decrease followed up to the phenophase open cluster. The main phenolic compounds were caffeoylquinic acids, coumaroylquinic acids and catechins, as well as quercetin and kaempferol derivatives. The data also support the protective role of ascorbate and glutathione in the para- and endodormancy phases. Consistent trends in the content of reducing sugars can be elucidated for the different phenophases of dormancy, too. The untargeted approach with principle component analysis (PCA) clearly differentiates the different timings of dormancy giving further valuable information.

Assessing the distribution of chloroplast DNA (cpDNA) haplotype variation is useful for studying the phylogeography of angiosperms. In the last two decades the cpDNA phylogeography of white oaks in Europe has been extensively studied, mostly based on the PCR-RFLP technique. However, PCR-RFLPs have low mutation rates and are primarily useful for reconstructing patterns at large geographical scales and lack resolution at fine spatial scales. Here we evaluate the usefulness of chloroplast microsatellites (cpSSR) as an alternative to PCR-RFLPs in Polish oak populations which have been underrepresented in previous studies. Eighty-five cpSSR haplotypes were detected using 14 cpSSR loci and a broad collection of 6680 trees sampled throughout Poland. Haplotype diversity was significantly lower in Q. petraea (He = 0.798) than in Q. robur (He = 0.820). Only 17 haplotypes (H01-H17) were found in 13 or more individuals, comprising together 97.9% of the sample. Most frequent cpSSR haplotypes were related to PCR-RFLP haplotypes, establishing the cross-references between the two marker systems. There was significant concordance between the matrices of genetic distances obtained by PCR-RFLP haplotypes and cpSSR haplotypes. Phylogenetic relationships among cpSSR haplotypes supported the existence of the three predominant maternal lineages of oaks in Poland: Iberian (7.8%), Apennine (20.6%) and Balkan (65.5%). The results are discussed with regards to the usefulness of cpSSR markers for phylogeographic studies.

Spring frost is a significant production hazard in nearly all temperate fruit-growing regions. Sweet cherries are among the first fruit varieties starting their development in spring and therefore highly susceptible to late frost. Temperatures at which injuries are likely to occur are widely published, but their origin and determination methods are not well documented. In this study, a standardized method was used to investigate critical frost temperatures for the sweet cherry cultivar 'Summit' under controlled conditions. Twigs were sampled at four development stages ("side green," "green tip," "open cluster," "full bloom") and subjected to three frost temperatures (-2.5, -5.0, -10.0 °C). The main advantage of this method, compared to other approaches, was that the exposition period and the time interval required to reach the target temperature were always constant (2 h). Furthermore, then, the twigs were placed in a climate chamber until full bloom, before the examination of the flowers and not further developed buds started. For the first two sampling stages (side green, green tip), the number of buds found in open cluster, "first white," and full bloom at the evaluation date decreased with the strength of the frost treatment. The flower organs showed different levels of cold hardiness and became more vulnerable in more advanced development stages. In this paper, we developed four empirical functions which allow calculating possible frost damages on sweet cherry buds or flowers at the investigated development stages. These equations can help farmers to estimate possible frost damages on cherry buds due to frost events. However, it is necessary to validate the critical temperatures obtained in laboratory with some field observations.

Grain harvesting is one of the most weather-dependent processes in agriculture. Grain moisture contents decide on machinery use and costs and determine the necessary grain harvesting and preservation capacities of farms. The objective of this work is to investigate whether and how recent climate changes in the German state of Brandenburg affect the available field time and the required combine harvester capacity. Weather data, the beginning of harvesting, available hours with defined grain moisture contents and total required harvesting capacity are analyzed for the years 1961–2013 for winter wheat, winter rye, winter barley and spring barley. The trends found differ for the four cereal crops. Compared with 53 years ago, today harvesting starts significantly earlier for two cereal crops (−16 days for spring barley and −11 days for winter wheat). The available harvesting hours show a clear and highly significant increase for winter wheat (up to +9%), a distinct and highly significant decrease for winter barley (up to −20%), as well as a slight and significant decrease for winter rye (up to −3%). Inter-annual variability decreases for winter wheat and increases for winter barley. The unfavorable changes for winter barley do not ultimately affect the total required machinery capacity due to the separate harvesting period and relatively small cropping area for winter barley. In contrast, the primarily favorable trends for winter wheat lead to an increase in the total required combine harvester capacity, since the earlier harvesting period overlaps with the rye harvesting period.

The Pan European Phenology (PEP) project is a European infrastructure to promote and facilitate phenological research, education, and environmental monitoring. The main objective is to maintain and develop a Pan European Phenological database (PEP725) with an open, unrestricted data access for science and education. PEP725 is the successor of the database developed through the COST action 725 “Establishing a European phenological data platform for climatological applications” working as a single access point for European-wide plant phenological data. So far, 32 European meteorological services and project partners from across Europe have joined and supplied data collected by volunteers from 1868 to the present for the PEP725 database. Most of the partners actively provide data on a regular basis. The database presently holds almost 12 million records, about 46 growing stages and 265 plant species (including cultivars), and can be accessed via http://www.pep725.eu/ . Users of the PEP725 database have studied a diversity of topics ranging from climate change impact, plant physiological question, phenological modeling, and remote sensing of vegetation to ecosystem productivity.

Some important stages of plant development, such as dormancy release and beginning of ontogenetic development, cannot be easily observed so that semi-mechanistic phenological models of spring phases mostly does not accurately reflect the control of these physiological stages. For this reason, over 6 years we studied weekly changes of Fresh Weight (FW), Dry Weight (DW), Water (WC), Nitrogen (NC) and Carbon Content (CC) in sweet cherry buds (Prunus avium L., cultivar ‘Summit’), from October to mid of April (stage ‘open cluster’, BBCH 56). Together with an experimental study to determine the date of endodormancy release, we were able to define the annual variability and average duration in the timing of para- endo-, and ecodormancy phase for sweet cherries, cultivar ‘Summit’. The secession of growth in autumn starts when all leafs has fallen down (BBCH 97) and marks the transition from para-to endodormancy. During endodormancy all investigated parameters reached a constant level which also did not change during ecodormancy. Our results showed that ecodormancy can be a relatively long phase in temperate climates, which must be adequately handled in phenological models. Beginning of ontogenetic development was clearly related to steadily rising water contents in cherry buds, which stayed stable during endo- and ecodormancy. Thus, this study highlights the importance of bud’s water content to define dormancy phases as well as beginning of ontogenetic development. The latter one was induced by continuously rising air temperatures above the freezing point. Physiologically, beginning of ontogenetic development is a flexible date which occurred on average 26 days before bud swelling was observed.

This study examined changes in sweet cherry buds of ‘Summit’ cultivar in four seasons (2011/12–2014/15) with respect to the nitrogen (N) content and the profile of eight free amino acids (asparagine (Asn), aspartic acid (Asp), isoleucine (Ile), glutamine (Gln), glutamic acid (Glu), arginine (Arg), alanine (Ala), histidine (His)). The presented results are to our knowledge the first under natural conditions in fruit tree orchards with a high temporal resolution from the dormant stage until cluster development. The N content in the buds from October, during endo- and ecodormancy until the beginning of ontogenetic development was a relatively stable parameter in each of the four seasons. The N accumulation into the buds began after ‘swollen bud’ and significant differences were visible at ‘green tip’ with an N content of 3.24, 3.12, 3.08, 2.40 which increased markedly to the mean of ‘tight’ and ‘open cluster’ by 3.77%, 3.78%, 3.44% and 3.10% in 2012–2015, respectively. In the buds, levels of asparagine were higher (up to 44 mg g−1 DW−1) than aspartic acid (up to 2 mg g−1 DW−1) and aspartic acid higher than isoleucine (up to 0.83 mg g−1 DW−1). Levels of glutamine were higher (up to 25 mg g−1 DW−1) than glutamic acid (up to 20 mg g−1 DW−1). The course of the arginine content was higher in 2011/12 compared to 2012/13, 2013/14 and 2014/15 which showed only slight differences. The alanine content in the buds was denoted in the four seasons only by relatively minor changes. The histidine content was higher in 2011/12 and 2012/13 compared to 2013/14 and 2014/15 which showed a comparable pattern. For 6 amino acids (Asn, Asp, Ile, Glu, Arg, Ala), the highest content was observed in 2012/13, the warmest period between swollen bud and open cluster. However in 2014/15, the season with the lowest mean temperature of 8.8 °C, only the content of Gln was the lowest. It was not possible to explain any seasonal differences in the amino acid content by environmental factors (air temperature) on the basis of few seasons. From none of the measured free amino acids could a clear determination of the date of endodormancy release (t1) or the beginning of the ontogenetic development (t1*) be derived. Therefore, these amino acids are no suitable markers to improve phenological models for the beginning of cherry blossom.