Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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    A blueprint of seed desiccation sensitivity in the genome of Castanospermum australe
    Correia Silva Santana Marques, A. ; Dias Costa, M.C. ; Chathuri, Udisha ; Jonkheer, Eef ; Zhao, T. ; Schijlen, E.G.W.M. ; Derks, M.F.L. ; Nijveen, H. ; Marcet-Houben, Marina ; Julca, Irene ; Delahaie, Julien ; Schranz, Eric ; Gabaldon, Toni ; Pelletier, S. ; Leprince, O. ; Ligterink, W. ; Buitink, J. ; Hilhorst, H.W.M. ; Farrant, Jill M. - \ 2019
    Most angiosperms produce seeds that are desiccated on dispersal with the ability to retain viability in storage facilities for prolonged periods. However, some species produce desiccation sensitive seeds which rapidly lose viability in storage, precluding ex situ conservation. Current consensus is that desiccation sensitive seeds either lack or do not express mechanisms necessary for the acquisition of desiccation tolerance. We sequenced the genome of Castanospermum australe, a legume species producing desiccation sensitive seeds, and characterized its seed developmental physiology and - transcriptomes. C. australe has a low rate of evolution, likely due to its perennial life-cycle and long generation times. The genome is syntenic with itself, with several orthologs of genes from desiccation tolerant legume seeds, from gamma whole-genome duplication events being retained. Changes in gene expression during development of C. australe seeds, as compared to desiccation tolerant Medicago truncatula seeds, suggest they remain metabolically active, prepared for immediate germination. Our data indicates that the phenotype of C. australe seeds arose through few changes in specific signalling pathways, precluding or bypassing activation of mechanisms necessary for acquisition of desiccation tolerance. Such changes have been perpetuated as the habitat in which dispersal occurs is favourable for prompt germination.
    Climate change, reforestation/afforestation, and urbanization impacts on evapotranspiration and streamflow in Europe
    Teuling, Adriaan J. ; Badts, Emile A.G. De; Jansen, Femke A. ; Fuchs, Richard ; Buitink, Joost ; Hoek Van Dijke, Anne J. ; Sterling, Shannon M. - \ 2019
    Hydrology and Earth System Sciences 23 (2019)9. - ISSN 1027-5606 - p. 3631 - 3652.

    Since the 1950s, Europe has undergone large shifts in climate and land cover. Previous assessments of past and future changes in evapotranspiration or streamflow have either focussed on land use/cover or climate contributions or on individual catchments under specific climate conditions, but not on all aspects at larger scales. Here, we aim to understand how decadal changes in climate (e.g. precipitation, temperature) and land use (e.g. deforestation/afforestation, urbanization) have impacted the amount and distribution of water resource availability (both evapotranspiration and streamflow) across Europe since the 1950s. To this end, we simulate the distribution of average evapotranspiration and streamflow at high resolution (1 km2) by combining (a) a steady-state Budyko model for water balance partitioning constrained by long-term (lysimeter) observations across different land use types, (b) a novel decadal high-resolution historical land use reconstruction, and (c) gridded observations of key meteorological variables. The continental-scale patterns in the simulations agree well with coarser-scale observation-based estimates of evapotranspiration and also with observed changes in streamflow from small basins across Europe. We find that strong shifts in the continental-scale patterns of evapotranspiration and streamflow have occurred between the period around 1960 and 2010. In much of central-western Europe, our results show an increase in evapotranspiration of the order of 5 %-15 % between 1955-1965 and 2005-2015, whereas much of the Scandinavian peninsula shows increases exceeding 15 %. The Iberian Peninsula and other parts of the Mediterranean show a decrease of the order of 5 %-15 %. A similar north-south gradient was found for changes in streamflow, although changes in central-western Europe were generally small. Strong decreases and increases exceeding 45 % were found in parts of the Iberian and Scandinavian peninsulas, respectively. In Sweden, for example, increased precipitation is a larger driver than large-scale reforestation and afforestation, leading to increases in both streamflow and evapotranspiration. In most of the Mediterranean, decreased precipitation combines with increased forest cover and potential evapotranspiration to reduce streamflow. In spite of considerable local- and regional-scale complexity, the response of net actual evapotranspiration to changes in land use, precipitation, and potential evaporation is remarkably uniform across Europe, increasing by ĝ1/4 35-60 km3 yr-1, equivalent to the discharge of a large river. For streamflow, effects of changes in precipitation (ĝ1/4 95 km3 yr-1) dominate land use and potential evapotranspiration contributions (ĝ1/4 45-60 km3 yr-1). Locally, increased forest cover, forest stand age, and urbanization have led to significant decreases and increases in available streamflow, even in catchments that are considered to be near-natural.

    The distributed simple dynamical systems (dS2) model
    Buitink, J. ; Melsen, L.A. ; Kirchner, J.W. ; Teuling, A.J. - \ 2019
    Wageningen : Wageningen University & Research
    hydrological model - rainfall-runoff - simple dynamical systems approach
    We present a new numerically robust distributed rainfall runoff model for computationally efficiency simulation at high (hourly) temporal resolution: the distributed simple dynamical systems (dS2) model. The model is based on the simple dynamical systems approach as proposed by Kirchner (2009), and the distributed implementation allows for spatial heterogeneity in the parameters and/or model forcing fields for instance as derived from precipitation radar data. The concept is extended with snow and routing modules, where the latter transports water from each pixel to the catchment outlet. The sensitivity function, which links changes in storage to changes in discharge, is implemented by a new 3-parameter equation that is able to represent the widely observed downward curvature in log-log space. The simplicity of the underlying concept allows the model to calculate discharge in a computationally efficient manner, even at high temporal and spatial resolution, while maintaining proven model performance at high temporal and spatial resolution. The model code is written in Python in order to be easily readable and adjustable while maintaining computational efficiency. Since this model has short run times, it allows for extended sensitivity and uncertainty studies with relatively low computational costs.
    Evaluating seasonal hydrological extremes in mesoscale (pre-)Alpine basins at coarse 0.5° and fine hyperresolution
    Buitink, Joost ; Uijlenhoet, Remko ; Teuling, Adriaan J. - \ 2019
    Hydrology and Earth System Sciences 23 (2019)3. - ISSN 1027-5606 - p. 1593 - 1609.

    Hydrological models are being applied for impact assessment across a wide range of resolutions. In this study, we quantify the effect of model resolution on the simulated hydrological response in five mesoscale basins in the Swiss Alps using the distributed hydrological model Spatial Processes in Hydrology (SPHY). We introduce a new metric to compare a range of values resulting from a distributed model with a single value: the density-weighted distance (DWD). Model simulations are performed at two different spatial resolutions, matching common practices in hydrology: 500m×500m matching regional-scale models, and 40km×40km matching global-scale modeling. We investigate both the intra-basin response in seasonal streamflow and evapotranspiration from the high-resolution model and the difference induced by the two different spatial resolutions, with a focus on four seasonal extremes, selected based on temperature and precipitation. Results from the high-resolution model show that the intra-basin response covers a surprisingly large range of anomalies and show that it is not uncommon to have both extreme positive and negative flux anomalies occurring simultaneously within a catchment. The intra-basin response was grouped by land cover, where different dominant runoff-generating processes are driving the differences between these groups. The low-resolution model failed to capture the diverse and contrasting response from the high-resolution model, since neither the complex topography nor land cover classes were properly represented. DWD values show that, locally, the hydrological response simulated with a high-resolution model can be a lot more extreme than a low-resolution model might indicate, which has important implications for global or continental scale assessments carried out at coarse grids of 0:5°×0:5° or 0:25°× 0:25° resolution.

    Key genes involved in desiccation tolerance and dormancy across life forms
    Costa, M.C.D. ; Farrant, Jill M. ; Oliver, Melvin J. ; Ligterink, Wilco ; Buitink, Julia ; Hilhorst, H.M.W. - \ 2016
    Plant Science 251 (2016). - ISSN 0168-9452 - p. 162 - 168.
    ABI3 - Arabidopsis thaliana - Conserved genes - Desiccation tolerance - Dormancy

    Desiccation tolerance (DT, the ability of certain organisms to survive severe dehydration) was a key trait in the evolution of life in terrestrial environments. Likely, the development of desiccation-tolerant life forms was accompanied by the acquisition of dormancy or a dormancy-like stage as a second powerful adaptation to cope with variations in the terrestrial environment. These naturally stress tolerant life forms may be a good source of genetic information to generate stress tolerant crops to face a future with predicted higher occurrence of drought. By mining for key genes and mechanisms related to DT and dormancy conserved across different species and life forms, unique candidate key genes may be identified. Here we identify several of these putative key genes, shared among multiple organisms, encoding for proteins involved in protection, growth and energy metabolism. Mutating a selection of these genes in the model plant Arabidopsis thaliana resulted in clear DT-, dormancy- and other seed-associated phenotypes, showing the efficiency and power of our approach and paves the way for the development of drought-stress tolerant crops. Our analysis supports a co-evolution of DT and dormancy by shared mechanisms that favour survival and adaptation to ever-changing environments with strong seasonal fluctuations.

    Time-series of the re-establishment of desiccation tolerance by ABA in germinated Arabidopsis thaliana seeds
    Dias Costa, Maria ; Righetti, K. ; Ligterink, Wilco ; Buitink, J. ; Hilhorst, Henk - \ 2015
    Wageningen University
    GSE62876 - Arabidopsis thaliana - GSE62876 - Arabidopsis thaliana - PRJNA265873
    Mature seeds of Arabidopsis thaliana are desiccation tolerant, but they lose DT while progressing to germination. Yet, there is a small developmental window during which DT can be rescued by treatment with abscisic acid (ABA).
    Lighting schedule and dimming period in early life: consequences for broiler chicken leg bone development
    Pol, C.W. van der; Molenaar, Roos ; Buitink, J. ; Roovert-Reijrink, I.A.M. van; Maatjens, C.M. ; Brand, H. van den; Kemp, B. - \ 2015
    Poultry Science 94 (2015)12. - ISSN 0032-5791 - p. 2980 - 2988.
    bone development - light-dark schedule - dimming - broiler
    Prolonged (>20 h) light periods during grow-out of broiler chickens have been shown to increase the occurrence of skeletal abnormalities, but the effects of early life light-dark schedules are not well known. The present experiment investigated the effect of lighting schedule and light-dark transition during the first days of a broiler chicken's life on leg bone development. In 2 experiments, Ross-308 broiler chicks (n = 2,500 per experiment) were subjected to 1 of 5 treatments for 4 d: 24L; 2L:1D lighting schedule with either an abrupt or gradual light-dark transition (“dimming”); and a 2L:6D lighting schedule with an abrupt transition or dimming. At d 4, tibia and femur weight, length, and diameter, yolk free body mass, organ weights, realized weight gain, feed intake, feed conversion ratio, and mortality were determined. In Experiment 2, chick length and relative asymmetry of the femur and tibia were determined additionally. Data were analyzed using orthogonal contrasts. 24L resulted in higher femur diameter (P < 0.028; both experiments), tibia diameter (P < 0.001; Experiment 1), relative asymmetry of tibia length (P = 0.002; Experiment 2), and relative asymmetry of femur length (P = 0.003) than applying a light-dark schedule. A 2L:1D lighting schedule resulted in higher femur length (P = 0.039; Experiment 1) and relative asymmetry of tibia length (P = 0.032; Experiment 2) and lower relative asymmetry of tibia diameter (P = 0.016) than a 2L:6D lighting schedule. An abrupt light-dark transition resulted in higher relative asymmetry of tibia length (P = 0.004; Experiment 2) and relative asymmetry of tibia diameter (P = 0.018) than dimming. To conclude, leg bone development in the first 4 d of a broiler chicken's life was higher for 24L than when a lighting schedule was applied, but relative asymmetry was higher as well, suggesting developmental instability. The effect of dimming on leg bone development was less pronounced, but the decreased relative asymmetry levels in the dimming treatment suggested lower environmental stress than for the abrupt light-dark transition.
    A gene co-expression network predicts functional genes controlling the re-establishment of desiccation tolerance in germinated Arabidopsis thaliana seeds
    Dias Costa, M.C. ; Righetti, K. ; Nijveen, H. ; Yazdanpanah, F. ; Ligterink, W. ; Buitink, J. ; Hilhorst, H.W.M. - \ 2015
    Planta 242 (2015)2. - ISSN 0032-0935 - p. 435 - 449.
    medicago-truncatula seeds - transcription factors - expression data - abiotic stress - dormancy - drought - identification - maturation - longevity - software
    Main conclusion During re-establishment of desiccation tolerance (DT), early events promote initial protection and growth arrest, while late events promote stress adaptation and contribute to survival in the dry state. Mature seeds of Arabidopsis thaliana are desiccation tolerant, but they lose desiccation tolerance (DT) while progressing to germination. Yet, there is a small developmental window during which DT can be rescued by treatment with abscisic acid (ABA). To gain temporal resolution and identify relevant genes in this process, data from a time series of microarrays were used to build a gene co-expression network. The network has two regions, namely early response (ER) and late response (LR). Genes in the ER region are related to biological processes, such as dormancy, acquisition of DT and drought, amplification of signals, growth arrest and induction of protection mechanisms (such as LEA proteins). Genes in the LR region lead to inhibition of photosynthesis and primary metabolism, promote adaptation to stress conditions and contribute to seed longevity. Phenotyping of 12 hubs in relation to re-establishment of DT with T-DNA insertion lines indicated a significant increase in the ability to re-establish DT compared with the wild-type in the lines cbsx4, at3g53040 and at4g25580, suggesting the operation of redundant and compensatory mechanisms. Moreover, we show that re-establishment of DT by polyethylene glycol and ABA occurs through partially overlapping mechanisms. Our data confirm that co-expression network analysis is a valid approach to examine data from time series of transcriptome analysis, as it provides promising insights into biologically relevant relations that help to generate new information about the roles of certain genes for DT.
    Time-series analysis of the transcriptome of the re-establishment of desiccation tolerance by ABA in germinated Arabidopsis thaliana seeds
    Dias Costa, M.C. ; Nijveen, H. ; Ligterink, W. ; Buitink, J. ; Hilhorst, H.W.M. - \ 2015
    Genomics Data 5 (2015). - ISSN 2213-5960 - p. 154 - 156.
    Expression analyses of time series have become a very popular method for studying the dynamics of a wide range of biological processes. Here, we present expression analysis of a time series with the help of microarrays used to study the re-establishment of desiccation tolerance (DT) in germinated Arabidopsis thaliana seeds. Mature seeds of A. thaliana are desiccation tolerant (survive the loss of most of their water content), but they become desiccation sensitive while progressing to germination. Yet, there is a small developmental window during which DT can be re-established by treatment with the plant hormone abscisic acid (ABA). We studied germinated A. thaliana seeds at the stage of radicle protrusion during ABA incubation for 0 h, 2 h, 12 h, 24 h and 72 h. We describe in detail the methodology applied for generating and analyzing this expression data of time series. The microarray raw data (http://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE62876) may be valuable for further studies on this experimental system, such as the construction of a gene co-expression network [1].
    Effect of light schedule and dimming in early life on bone developement in the broiler chicken
    Pol, C.W. van der; Buitink, C.J. ; Maatjens, C.M. ; Roovert-Reijrink, I.A.M. van; Brand, H. van den; Molenaar, R. - \ 2013
    MtPM25 is an atypical hydrophobic late embryogenesis-abundant protein that dissociates cold and desiccation-aggregated proteins
    Boucher, V. ; Buitink, J. ; Lin, X. ; Boudet, J. ; Hoekstra, F.A. ; Hundertmark, M. ; Renard, D. ; Leprince, O. - \ 2010
    Plant, Cell & Environment 33 (2010)3. - ISSN 0140-7791 - p. 418 - 430.
    medicago-truncatula seeds - lea proteins - arabidopsis-thaliana - aqueous-solution - dry state - in-vitro - tolerance - germination - stress - water
    Late embryogenesis-abundant (LEA) proteins are one of the components involved in desiccation tolerance (DT) by maintaining cellular structures in the dry state. Among them, MtPM25, a member of the group 5 is specifically associated with DT in Medicago truncatula seeds. Its function is unknown and its classification as a LEA protein remains elusive. Here, evidence is provided that MtPM25 is a hydrophobic, intrinsically disordered protein that shares the characteristics of canonical LEA proteins. Screening protective activities by testing various substrates against freezing, heating and drying indicates that MtPM25 is unable to protect membranes but able to prevent aggregation of proteins during stress. Prevention of aggregation was also found for the water soluble proteome of desiccation-sensitive radicles. This inhibition was significantly higher than that of MtEM6, one of the most hydrophilic LEA protein associated with DT. Moreover, when added after the stress treatment, MtPM25 is able to rapidly dissolve aggregates in a non-specific manner. Sorption isotherms show that when it is unstructured, MtPM25 absorbs up to threefold more water than MtEM6. MtPM25 is likely to act as a protective molecule during drying and plays an additional role as a repair mechanism compared with other LEA proteins.
    Dormancy in Plant Seeds
    Hilhorst, H.W.M. ; Finch-Savage, W.E. ; Buitink, J. ; Bolingue, W. ; Leubner-Metzger, G. - \ 2010
    In: Dormancy and Resistance in Harsh Environments / Cerda, J., Clark, M., Lubzens, E., Heidelberg : Springer-Verlag, Berlin (Topics in Current Genetics 21) - ISBN 9783642124211 - p. 43 - 67.
    Seed dormancy has been studied intensely over the past decades and, at present, knowledge of this plant trait is at the forefront of plant biology. The main model species is Arabidopsis thaliana, an annual weed, possessing nondeep physiological dormancy. This overview presents the state-of-the-art of seed dormancy research, focusing mainly on physiological and molecular-genetic aspects in this species. It has become clear that, like in many other organisms, the dormancy and stress responses are tightly associated in seeds. The plant hormones abscisic acid and gibberellins play a pivotal role in the acquisition of developmental arrest or repression of metabolic inactivity, respectively. Some attention is given to the overlapping dormancy and stress responses, commonly studied in many other organisms but only marginally in seeds
    Comparative analysis of the heat stable proteome of radicles of Medicago truncatula seeds during germination identifies late embryogenesis abundant proteins associated with desiccation tolerance
    Boudet, J. ; Buitink, J. ; Hoekstra, F.A. ; Rogniaux, H. ; Larré, C. ; Satour, P. ; Leprince, O. - \ 2006
    Plant Physiology 140 (2006). - ISSN 0032-0889 - p. 1418 - 1436.
    arabidopsis-thaliana - secondary structure - abscisic-acid - lea protein - saccharomyces-cerevisiae - cellular-localization - dehydration tolerance - freezing tolerance - gene-expression - reference maps
    A proteomic analysis was performed on the heat stable protein fraction of imbibed radicles of Medicago truncatula seeds to investigate whether proteins can be identified that are specifically linked to desiccation tolerance (DT). Radicles were compared before and after emergence (2.8 mm long) in association with the loss of DT, and after reinduction of DT by an osmotic treatment. To separate proteins induced by the osmotic treatment from those linked with DT, the comparison was extended to 5 mm long emerged radicles for which DT could no longer be reinduced, albeit that drought tolerance was increased. The abundance of 15 polypeptides was linked with DT, out of which 11 were identified as late embryogenesis abundant proteins from different groups: MtEm6 (group 1), one isoform of DHN3 (dehydrins), MtPM25 (group 5), and three members of group 3 (MP2, an isoform of PM18, and all the isoforms of SBP65). In silico analysis revealed that their expression is likely seed specific, except for DHN3. Other isoforms of DNH3 and PM18 as well as three isoforms of the dehydrin Budcar5 were associated with drought tolerance. Changes in the abundance of MtEm6 and MtPM25 in imbibed cotyledons during the loss of DT and in developing embryos during the acquisition of DT confirmed the link of these two proteins with DT. Fourier transform infrared spectroscopy revealed that the recombinant MtPM25 and MtEm6 exhibited a certain degree of order in the hydrated state, but that they became more structured by adopting helices and sheets during drying. A model is presented in which DT-linked late embryogenesis abundant proteins might exert different protective functions at high and low hydration levels.
    Changes in DNa and microtubules during loss and re-establishment of desiccation tolerance in germinating Medicago truncatula seeds
    Faria, J.M.R. ; Buitink, J. ; Lammeren, A.A.M. van; Hilhorst, H.W.M. - \ 2005
    Journal of Experimental Botany 56 (2005)418. - ISSN 0022-0957 - p. 2119 - 2130.
    celcyclus - uitdrogingstolerantie - dna - medicago truncatula - microtubuli - cell cycle - desiccation tolerance - dna - medicago truncatula - microtubules - nuclear replication activity - programmed cell-death - hydration-dehydration - recalcitrant seeds - plant-cells - fragmentation - localization - integrity - radicles - survival
    Desiccation tolerance (DT) in orthodox seeds is acquired during seed development and lost upon imbibition/germination, purportedly upon the resumption of DNA synthesis in the radicle cells. In the present study, flow cytometric analyses and visualization of microtubules (MTs) in radicle cells of seedlings of Medicago truncatula showed that up to a radicle length of 2 mm, there is neither DNA synthesis nor cell division, which were first detected in radicles with a length of 3 mm. However, DT started to be lost well before the resumption of DNA synthesis, when germinating seeds were dried back. By applying an osmotic treatment with polyethylene glycol (PEG) before dehydration, it was possible to re-establish DT in seedlings with a radicle up to 2 mm long. Dehydration of seedlings with a 2 mm radicle, with or without PEG treatment, caused disassembly of MTs and appearance of tubulin granules. Subsequent pre-humidification led to an almost complete disappearance of both MTs and tubulin granules. Upon rehydration, neither MTs nor tubulin granules were detected in radicle cells of untreated seedlings, while PEG-treated seedlings were able to reconstitute the microtubular cytoskeleton and continue their normal development. Dehydration of untreated seedlings also led to an apoptotic-like DNA fragmentation in radicle cells, while in PEG-treated seedlingss DNA integrity was maintained. The results showed that for different cellular components, desiccation-tolerant seedlings may apply distinct strategies to survive dehydration, either by avoidance or further repair of the damages
    Understanding and predicting optimal storage conditions and longevity: a biophysical approach
    Buitink, J. ; Hoekstra, F.A. - \ 2003
    In: Seed conservation: turning science into practice / Smith, R.D., Dickie, J.B., Linington, S.L., Pritchard, H.W., Probert, R.J., Kew : Kew: Royal Botanic Gardens - p. 518 - 529.
    Biochemistry and biophysics of tolerance systems
    Buitink, J. ; Hoekstra, F.A. ; Leprince, O. - \ 2002
    In: Desiccation and survival in plants: drying without dying / Black, M., Pritchard, H.W., Wallingford : CABI - p. 293 - 318.
    plantenweefsels - verdroging - biochemie - biofysica - tolerantie - plant tissues - desiccation - biochemistry - biophysics - tolerance
    Mechanisms of plant desiccation tolerance.
    Hoekstra, F.A. ; Golovina, E.A. ; Buitink, J. - \ 2001
    Trends in Plant Science 6 (2001). - ISSN 1360-1385 - p. 431 - 438.
    Anhydrobiosis (`life without water') is the remarkable ability of certain organisms to survive almost total dehydration. It requires a coordinated series of events during dehydration that are associated with preventing oxidative damage and maintaining the native structure of macromolecules and membranes. The preferential hydration of macromolecules is essential when there is still bulk water present, but replacement by sugars becomes important upon further drying. Recent advances in our understanding of the mechanism of anhydrobiosis include the downregulation of metabolism, dehydration-induced partitioning of amphiphilic compounds into membranes and immobilization of the cytoplasm in a stable multicomponent glassy matrix.
    A study of water relations in neem (Azadirachta indica) seed that is characterised by complex storage behaviour
    Sacandé, M. ; Buitink, J. ; Hoekstra, F.A. - \ 2000
    Journal of Experimental Botany 51 (2000). - ISSN 0022-0957 - p. 635 - 643.
    Neem (Azadirachta indica) seed is reputed to have limited tolerance to desiccation, to be sensitive to chilling and imbibitional stress, and to display intermediate storage behaviour. To understand this behaviour the properties of water in seed tissues were studied. Water sorption isotherms showed that at similar relative humidity (RH), the water content was consistently higher in axes than in cotyledons, mainly due to the elevated lipid content (51€in the cotyledons. Using differential scanning calorimetry, melting transitions of water were observed at water contents higher than 0.14 g H2O g-1 DW in the cotyledons and 0.23 g H2O g-1 DW in the axes. Beside melting transitions of lipid, as verified by infrared spectroscopy, changes in heat capacity were observed which shifted with water content, indicative of glass-to-liquid transitions. State diagrams are given on the basis of the water content of seed tissues, and also on the basis of the RH at 20 °C. Longevity was considerably improved, and the sensitivity to chilling/subzero temperatures was reduced when axis and cotyledons were dehydrated to moisture contents of approximately 0.05 g H2O g-1 DW. However, longevity during storage at very low water contents was limited. A possible mechanism for the loss of sensitivity to chilling/subzero temperatures at low water contents is discussed. The results suggest that dry neem seeds in the glassy state have great potential for extended storability, also at subzero temperatures
    Molecular mobility in the cytoplasm : An approach to describe and predict lifespan of dry germplasm
    Buitink, J. ; Leprince, O. ; Hemminga, M.A. ; Hoekstra, F.A. - \ 2000
    Proceedings of the National Academy of Sciences of the United States of America 97 (2000). - ISSN 0027-8424 - p. 2385 - 2390.
    Molecular mobility is increasingly considered a key factor influencing storage stability of biomolecular substances, because it is thought to control the rate of detrimental reactions responsible for reducing the shelf life of, for instance, pharmaceuticals, food, and germplasm. We investigated the relationship between aging rates of germplasm and the rotational motion of a polar spin probe in the cytoplasm under different storage conditions using saturation transfer electron paramagnetic resonance spectroscopy. Rotational motion of the spin probe in the cytoplasm of seed and pollen of various plant species changed as a function of moisture content and temperature in a manner similar to aging rates or longevity. A linear relationship was established between the logarithms of rotational motion and aging rates or longevity. This linearity suggests that detrimental aging rates are associated with molecular mobility in the cytoplasm. By measuring the rotational correlation times at low temperatures at which experimental determination of longevity is practically impossible, this linearity enabled us to predict vigor loss or longevity. At subzero temperatures, moisture contents for maximum life span were predicted to be higher than those hitherto used in genebanks, urging for a reexamination of seed storage protocols.
    The effects of moisture and temperature on the ageing kinetics of pollen : Interpretation based on cytoplasmic mobility
    Buitink, J. ; Leprince, O. ; Hemminga, M.A. ; Hoekstra, F.A. - \ 2000
    Plant, Cell & Environment 23 (2000). - ISSN 0140-7791 - p. 967 - 974.
    This study shows that characterization of the molecular mobility in the cytoplasm of pollen provides a new understanding of the effects of moisture and temperature on ageing rates. Using EPR spectroscopy, we determined the rotational motion of the polar spin probe, 3-carboxy-proxyl, in the cytoplasm of Typha latifolia pollen, under different temperature and moisture content conditions. Increasing the temperature resulted in faster rotational motion, analogous to faster ageing rates. With decreasing moisture content, rotational motion first decreased until a minimum was reached, after which rotational motion slightly increased again. The moisture content at which this minimal rotational motion was observed increased with decreasing temperature, comparable to the pattern of ageing rate. A significant linear relationship was found between ageing rates and rotational motion in the cytoplasm, suggesting that these parameters are causally linked. Upon melting of the intracellular glass, a twofold increase in activation energy of rotational motion and ageing rate was observed. In contrast, melting of the sucrose glass resulted in an increase in rotational motion of five orders of magnitude. The difference in rotational motion upon melting glasses of pollen or sucrose suggests that other molecules beside sugars play a role in intracellular glass formation in pollen.
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