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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Physiological responses of rice to increased day and night temperatures
Shi, Wanju - \ 2017
University. Promotor(en): Paul Struik, co-promotor(en): Xinyou Yin. - Wageningen : Wageningen University - ISBN 9789463437110 - 202
crops - rice - oryza sativa - plant physiology - temperature - crop yield - grain - agronomy - gewassen - rijst - plantenfysiologie - temperatuur - gewasopbrengst - graan - agronomie

A more rapid increase in night-time temperature compared with day-time temperature and the increased frequency of heat waves associated with climate change present a serious threat to rice (Oryza sativa L.) production and food security. This thesis aims to understand the impact of high night-time temperature (HNT) and high day-time temperature (HDT) on rice grain yield and grain quality and to examine adaptation strategies to cope with high-temperature stresses.

Grain yield and quality of a susceptible indica genotype (Gharib) and all tested hybrids, when exposed to HNT in the field, were significantly reduced across seasons, with less average reduction in the dry season than in the wet season, indicating that other environmental factors under field conditions may contribute to impacts of HNT on yield. Among the different yield components, a reduced number of spikelets m−2 significantly contributed to yield loss under HNT followed by the consistently lower single-grain weight across all genotypes, while the impact of the decrease in percentage seed-set was less and season-specific. Lower grain yield and poorer grain quality in susceptible cultivar Gharib were associated with a significant reduction in non-structural carbohydrate translocation after flowering, resulting in reduced grain-filling duration. Increased total nitrogen application did not alleviate the negative impact of HNT. The proposed model approach showed that there were significant differences among cultivars in their changes in source-sink relationships in response to HNT. Given that rice grain yield and quality are challenged by a rise in HDT and HNT, in particular at flowering and during grain filling, differential impacts of HNT and HDT during these critical stages were observed. For the single-grain growth during grain filling, HDT either independently or in combination with HNT exerted greater influences than HNT on the grain filling dynamics, activities of starch metabolism enzymes, temporal starch accumulation patterns, and the process of chalk formation. During flowering, HDT increased spikelet sterility in tested hybrids and hybrids were less tolerant to high temperatures than high-yielding inbred varieties. Moreover, in contrast with HNT, HDT played a dominant role in determining spikelet fertility. Novel observations with a series of snapshots of dynamic fertilization processes demonstrated that disturbances in the pre-fertilization phase were the primary causes for heat-induced spikelet sterility, indicating the effectiveness of employing the early-morning flowering trait for mitigating the impact of heat stress at flowering on rice.

A floor cover to improve temperature distribution and quality preservation in maritime refrigerated container transport of grapes : GreenCHAINge WP1 - Table Grapes
Lukasse, Leo ; Mensink, Manon ; Wissink, Edo - \ 2017
Wageningen : Wageningen Food & Biobased Research (Wageningen Food & Biobased Research report 1733) - ISBN 9789463436601 - 32
refrigerated transport - containers - sea transport - grapes - covers - temperature - food quality - koeltransport - zeetransport - druiven - bedekkingsmaterialen - temperatuur - voedselkwaliteit
Like many other fruits, table grapes depend on accurate temperature management during transport in maritime refrigerated containers. Ideally the temperature inside the container is equal to set point in every location in the container. Unfortunately door-end temperatures are always higher due to poor air flow distribution. In climate chamber tests Lukasse & Staal (2016a and 2016b) investigated the effect of covering sections of the container’s T-bar floor. The best T-bar floor cover found in that study was a trapezoid-shape floor cover. The aim of this study is to assess the effect of that trapezoid-shape T-bar floor cover on temperature and fruit quality in commercial reefer container transports of grapes. A field experiment was done in a commercial container shipment of six standard 40 ft. HC reefer containers travelling from South Africa to The Netherlands taking 24 days. The three test containers contained a T-bar floor cover. The three reference containers did not contain the T-bar floor cover. All other parameters were, to the extent possible, the same for all containers. In 31 locations air temperature between the fruit was logged at an interval of 10 min. with an accuracy of approx. ± 0.1 °C. 15 Trays, evenly distributed in a vertical plane on the container’s longitudinal centre line, were weighed at origin and at destination. At destination the fruit quality of these 15 trays was analysed. A clear positive effect on temperature was observed. The floor cover reduces the average difference between warmest and coldest temperature in the trays by approx. 30%. An effect on grape quality could not be assessed.
Metropolitan solutions: Droge voeten in een groene stad
Hattum, T. van - \ 2017
Wageningen : Wageningen University & Research
klimaat - hittetolerantie - stedelijke gebieden - luchtkwaliteit - regenwateropvang - temperatuur - climate - heat tolerance - urban areas - air quality - water harvesting - temperature
Door klimaatverandering krijgen we steeds vaker te maken met hevige regenval en periodes van extreme hitte en droogte. Veel steden zijn hier niet tegen opgewassen en moeten anders ingericht gaan worden. Groene oplossingen kunnen wateroverlast beperken, de temperatuur verlagen en de luchtkwaliteit verbeteren. Tim van Hattum van Wageningen University & Research vertelt er alles over.
Gezondheidseffecten onder de loep : weldadig groen
Spijker, J.H. ; Vries, S. de - \ 2017
Stadswerk (2017)6. - ISSN 0927-7641 - p. 34 - 36.
gezondheid - warmtestress - temperatuur - kwaliteit - beplantingen - biodiversiteit - stedelijke gebieden - bevolking - stressfactoren - sociaal welzijn - klimaat - health - heat stress - temperature - quality - plantations - biodiversity - urban areas - human population - stress factors - social welfare - climate
Groen speelt een sleutelrol bij een gezonde leefomgeving. De gezondheidseffecten spelen op diverse manieren, maar vooral door de stressverlagende effecten van groen en de hittedempende werking op warme dagen. Het is daarbij wel belangrijk om niet alleen naar de kwantiteit maar ook naar de kwaliteit van het groen te kijken.
Greenery and residential : a summary of the positive effects of greenery on well-being in residential
Hiemstra, J.A. ; Vries, S. de; Spijker, J.H. - \ 2017
Wageningen University & Research - 7 p.
residential areas - housing - plantations - public green areas - gardens - domestic gardens - health indicators - green roofs - green walls - temperature - climate - heat stress - health - woonwijken - huisvesting - beplantingen - openbaar groen - tuinen - tuinen bij het huis - gezondheidsindicatoren - groene daken - groene gevels - temperatuur - klimaat - warmtestress - gezondheid
Greenery and residential : a summary of the positive effects of greenery on well-being in residential
Crop growth and development in closed and semi-closed greenhouses
Qian, Tian - \ 2017
University. Promotor(en): Leo Marcelis, co-promotor(en): Anja Dieleman; Anne Elings. - Wageningen : Wageningen University - ISBN 9789463430708 - 112
crops - crop production - growth - greenhouse crops - greenhouse horticulture - climate - semi-closed greenhouses - photosynthesis - temperature - gewassen - gewasproductie - groei - kasgewassen - glastuinbouw - klimaat - semi-gesloten kassen - fotosynthese - temperatuur

(Semi-)closed greenhouses have been developed over the last decades to conserve energy. In a closed greenhouse, window ventilation is fully replaced by mechanical cooling while solar heat is temporarily stored in an aquifer. A semi-closed greenhouse has a smaller cooling capacity than a closed greenhouse and, in which mechanical cooling is combined with window ventilation. (Semi-)closed greenhouses create new climate conditions: high CO2 concentrations irrespective of the outdoor climate, and vertical gradients in temperature and vapour pressure deficit throughout the canopy. This thesis focuses on the crop physiology in (semi-)closed greenhouses, and investigates the effects of the new climate conditions on crop growth, development and underlying processes.

Cumulative production in (semi) closed greenhouses increased by 6-14% compared to the open greenhouse, depending on the cooling capacity. The production increase in the (semi-)closed greenhouses was explained by the higher CO2 concentrations. In many species, feedback inhibition of photosynthesis occurs when plants are grown at high CO2. The results, however, suggest that high CO2 concentrations do not cause feedback inhibition in high producing crops, because the plants have sufficient sink organs (fruits) to utilise all assimilates. Pruning experiments showed that photosynthetic acclimation to elevated CO2 concentration only occurred when the number of fruits was considerably reduced.

Cooling below the canopy induced vertical temperature and vapour pressure deficit gradients. These gradients correlated with outside radiation and outside temperature. Despite the occurrence of vertical temperature gradients, plant growth and fruit yield were mostly unaffected. Leaf and truss initiation rates did not differ in the presence or absence of a vertical temperature gradients, since air temperatures at the top of the canopy were kept comparable. The only observed response of plants to the vertical temperature gradient was the reduced rate of fruit development in the lower part of the canopy. This resulted in a longer period between anthesis and fruit harvest and an increase in the average fruit weight in summer. However, total fruit production over the whole season was not affected.

The effects of the climate factors light, CO2 concentration, temperature, and humidity on leaf photosynthesis were investigated. The photosynthesis model of Farquhar, von Caemmerer and Berry (FvCB) was modified by adding a sub-model for Ribulose-1,5-bisphosphate carboxylase (Rubisco) activation. The photosynthetic parameters: the maximum carboxylation capacity (Vcmax) and the maximum electron transport rate (Jmax), α (the efficiency of light energy conversion), θ (the curvature of light response of electron transport), and Rd (the non-photorespiratory CO2 release) were estimated based on measurements under a wide range of environmental conditions in the semi-closed greenhouse. The simultaneous estimation method and the nonlinear mixed effects model were applied to ensure the accuracy of the parameter estimation. Observations and predictions matched well (R2=0.94).

The yield increase in a closed greenhouse, compared to that in an open greenhouse was analyzed based on physiological and developmental processes. The yield increase in the (semi-)closed greenhouses was the result of an increase of net leaf photosynthesis. The (semi-)closed greenhouses have been applied commercially first in the Netherlands, and later in other countries. The knowledge obtained from (semi-)closed greenhouses is applied in conventional open greenhouse as well, which is called the next generation greenhouse cultivation. A number of innovations are being developed for greenhouse industry to reduce energy consumption while improving production and quality.

Groen en wonen : de meerwaarde van groen voor het welbevinden in de woonomgeving samengevat
Spijker, J.H. - \ 2017
- 7 p.
woonwijken - huisvesting - beplantingen - openbaar groen - tuinen - tuinen bij het huis - gezondheidsindicatoren - culturele waarden - hoveniers - groene daken - groene gevels - temperatuur - plaatsbepaling van bomen - klimaat - warmtestress - welzijn - residential areas - housing - plantations - public green areas - gardens - domestic gardens - health indicators - cultural values - landscape gardeners - green roofs - green walls - temperature - tree orientation - climate - heat stress - well-being
Groen in en rondom woonhuizen en appartementen is goed voor het (leef)klimaat binnen en buiten de woning. Het heeft een positief effect op de gezondheid en het algehele welbevinden van bewoners en bezoekers en verhoogt de waarde van het vastgoed. Dit document biedt meer inzicht in de voordelen van groen in relatie tot wonen en welbevinden, inclusief verwijzingen naar de wetenschappelijke onderbouwing. Het document sluit af met tips die helpen om groen succesvol en volwaardig toe te passen
Groen en herstellen : de meerwaarde van groen voor het welbevinden in de herstelomgeving samengevat
Spijker, J.H. - \ 2017
- 6 p.
welzijn - gezondheid - gezondheidsindicatoren - tuinen - warmtestress - klimaat - temperatuur - luchtkwaliteit - stress - sociaal welzijn - participatie - beplantingen - herstellen - well-being - health - health indicators - gardens - heat stress - climate - temperature - air quality - social welfare - participation - plantations - reconditioning
Groen in en rondom verzorgingshuizen, ziekenhuizen en overige klinieken is goed voor het klimaat binnen en buiten de instelling en heeft een positief effect op het herstellend vermogen en de gemoedstoestand van patiënten, en het algehele welbevinden van patiënten, medewerkers en bezoekers. Dit document biedt meer inzicht in de voordelen van groen in relatie tot herstellen en welbevinden, inclusief verwijzingen naar de wetenschappelijke onderbouwing. Het document sluit af met tips die helpen om groen succesvol en volwaardig toe te passen.
Groen en leren : de meerwaarde van groen voor het welbevinden in de leeromgeving samengevat
Spijker, J.H. - \ 2017
- 7 p.
beplantingen - onderwijs - leren - schoolterrein - leerprestaties - openbaar groen - klimaat - temperatuur - gezondheid - sociaal welzijn - luchtkwaliteit - lichamelijke activiteit - lichamelijke fitheid - stressfactoren - kinderen - plantations - education - learning - school site - educational performance - public green areas - climate - temperature - health - social welfare - air quality - physical activity - physical fitness - stress factors - children
de meerwaarde van groen voor het welbevinden in de leeromgeving samengevat
Temperature in water and sediment in the pesticide model TOXSWA : implementation report
Beltman, W.H.J. ; Adriaanse, P.I. ; Jacobs, C.M.J. ; Mulder, H.M. - \ 2017
Wageningen : Wageningen Environmental Research (Wageningen Environmental Research report 2794) - 67
pesticides - water - temperature - models - sediment - surface water - pesticiden - temperatuur - modellen - oppervlaktewater
TOXSWA simuleert het gedrag van stoffen in oppervlaktewater om blootstellingsconcentratie te berekenen voor organismen die in water of sediment leven, als onderdeel van de aquatische risicobeoordeling van gewasbeschermingsmiddelen (GBM). Het vernieuwde concept voor de beschrijving van de temperatuur in het TOXSWA model werd getest aan de hand van een bestaande implementatie van het 1D bulk model.
The hot, the cold and the tulip : the regulation of flowering time and dormancy release
Leeggangers, Hendrika A.C.F. - \ 2017
University. Promotor(en): Richard Immink, co-promotor(en): Henk Hilhorst. - Wageningen : Wageningen University - ISBN 9789463430289 - 244
tulipa - lilium - tulips - flowering date - flowering - dormancy - plant development - temperature - plant physiology - vegetative propagation - tulpen - bloeidatum - bloei - slaaptoestand - plantenontwikkeling - temperatuur - plantenfysiologie - vegetatieve vermeerdering

The ornamental geophyte Tulipa gesneriana is the most cultivated bulbous species in the Netherlands. It is widely grown in the field for vegetative propagation purposes and in greenhouses for the production of high quality cut flowers. Over the last decade, the tulip bulb industry is affected by the rapid climate change the world is facing. Temperature is rising and influences the vegetative to reproductive phase change (floral induction) inside the tulip bulbs in spring and processes that are occurring during winter, such as dormancy release.

In this thesis the two temperature-dependent processes related to tulip flowering, being floral induction and dormancy release, were investigated in detail with a special focus at the molecular level. Flowering time has been studied in a broad range of species, including the model species Arabidopsis thaliana and Oryza sativa. The current understanding of this process can be translated to non-model species, such as tulip, through a ‘bottom-up’ and ‘top-down’ approach (Chapter 2). For the ‘bottom-up’ approach conservation of molecular pathways is assumed and researchers make use of sequence homology searches to identify candidate genes. The ‘top-down’ approach starts from large scale data mining, such as RNA-sequencing (RNA-seq) data or microarrays, followed by the association between phenotypes, genes and gene expression patterns. Here, a comparison with data from model plant species is made at the end of the process and this also leads to the identification of candidate genes for a particular process.

Large scale genomics data mining in tulip is only possible via transcriptome analysis with RNA-seq derived data, because no full genome-sequence is present at this moment. Genome sequencing remains a challenge for species with a large and complex genome, containing probably a large number of repetitive sequences, which is the case for tulip and lily. In chapter 3 a high quality transcriptome of tulip and lily is presented, which is derived from a collection of different tissues. In order to obtain good transcriptome coverage and to facilitate effective data mining, different filtering parameters were used. This analysis revealed the limitations of commonly applied methods used in de novo transcriptome assembly. The generated transcriptome for tulip and lily is made publicly available via a user friendly database, named the ‘Transcriptome Browser’.

The molecular regulation of the temperature-dependent floral induction was studied through the use of RNA-seq (Chapter 4). A better understanding of this process is needed to prevent floral bud blasting (dehydration of the flower) in the future. The development at the shoot apical meristem (SAM) was morphologically investigated in two contrasting temperature environments, high and low. Meristem-enriched tissues were collected before and during the start of flower development. The start of flower development is morphologically visible by rounding of the SAM and correlates with the up-regulation of TGSQA, an AP1-like gene. A ‘top-down’ approach was used to identify possible regulators of the floral induction in tulip. However, Gene ontology (GO)-enrichment analysis of the differentially expressed genes showed that the floral induction, maturation of the bulb and dormancy establishment are occurring around the same period in time. Therefore a ‘bottom-up’ approach was followed to identify specific flowering time regulators based on knowledge obtained from other species. Expression analysis in tulip, heterologous analysis in Arabidopsis and yeast two hybrid-based protein-protein interaction studies revealed that Tulipa gesneriana TERMINAL FLOWER 1 (TgTFL1) is likely a repressor of flowering, whereas Tulipa gesneriana SUPPRESSOR OF OVEREXPRESSION OF CONSTANS-LIKE2 (TgSOC1L2) acts probably as a floral activator.

Another well-known flowering time regulator is FLOWERING LOCUS T (FT), which is a member of the PEBP gene family found in Arabidopsis and many more plant species. In tulip and lily, a total of four highly similar sequences to FT and HEADING DATA 3A (Hd3a) were identified (Chapter 5). Overexpression of Lilium longiflorum FT (LlFT) and TgFT2 in Arabidopsis resulted in an early flowering phenotype, but upon overexpression of TgFT1 and TgFT3 a late flowering phenotype was observed. The tulip PEBP genes TgFT2 and TgFT3 have a similar expression pattern during development, but show a different behaviour in Arabidopsis. Therefore the difference within the amino acid sequence was investigated, which resulted in the identification of two important amino acids for the FT function, which appeared to be mutated in TgFT3. Interchanging of these amino acids between TgFT2 and TgFT3 resulted in conversion of the phenotype, showing the potential importance of these positions in the protein and these specific amino acids for the molecular mode of action of these two proteins. Based on all the data, LlFT is considered to play a role in creating meristem competency to flowering related cues and TgFT2 to act as a florigen involved in the floral induction. The function of TgFT3 is not clear, but phylogenetic analysis suggests a bulb specific function.

After the floral induction and completion of flower development inside the tulip bulb, a period of prolonged cold is required for proper flowering in spring. Low temperature stimulates the re-mobilization of carbohydrates from the scale tissues to the sink organs, such as the floral stem, floral bud and leaves. Not many details are known about the molecular and metabolic changes during this cold period. In chapter 6, first insights are shown on the development of the different tissues inside the bulbs. The floral bud appears to be the least active tissue in comparison with the floral stem and leaves, suggesting a type of floral bud dormancy in tulip. However, metabolic changes are suggesting that the floral bud is still showing active cell division and/or preparation for elongation by turgor-driven cell wall extension. Dormancy of all tissues seems to be released ten weeks after planting and is correlated with the increase of glucose levels. In the leaves, from this same moment, photosynthesis related genes are up-regulated suggesting that the leaves are preparing for photosynthesis while still beneath the soil surface.

At the end of the thesis a glance is given at different perspectives of the tulips life cycle, categorizing tulip as a perennial, biennial or annual plant species, respectively. The perennial way of life is applicable when growing bulbs from seeds, while biennial and annual are more in relation to vegetative propagation. Also the importance of bulb size is highlighted, because it will determine if the bulbs are able to flower or not the following spring. Two scenarios are discussed related to availability of energy in the presence of carbohydrates and meristem incompetency to floral inducing signals. Throughout all research done for this thesis, it became clear that tulip bulbs and seeds have a lot in common. By combining the knowledge of processes in different plant species or developmental systems it is possible to understand how flowering and dormancy release are regulated and this provides us with novel insights how these processes are regulated in bulbous plant species, such as tulip.

Koudetolerantie Phalaenopsis : GreenCHAINge onderzoek potplanten 2016
Harkema, Harmannus ; Hogeveen, Esther ; Otma, Els ; Leentfaar, Gerard - \ 2017
Wageningen : Wageningen Food & Biobased Research (Wageningen Food & Biobased Research rapport 1698) - ISBN 9789463430593 - 48
koudebeschadiging - potplanten - orchideeën als sierplanten - koudeopslag - temperatuur - gevoeligheidsanalyse - chilling injury - pot plants - ornamental orchids - cold storage - temperature - sensitivity analysis
Ambient temperature‐directed flowering time regulation : the role of alternative splicing
Verhage, Dina Sara Leonie - \ 2017
University. Promotor(en): Gerco Angenent, co-promotor(en): Richard Immink; Guusje Bonnema. - Wageningen : Wageningen University - ISBN 9789462579705 - 161
plants - flowering date - flowering - temperature - alternative splicing - molecular biology - genes - planten - bloeidatum - bloei - temperatuur - alternatieve splitsing - moleculaire biologie - genen

As a consequence of a sessile lifestyle, plants are constantly facing a fluctuating environment. In order to both profit maximally and protect themselves from these environmental cues, plants evolved ways to sense and respond to signals.

Ambient temperature is one of the cues for which plants have acquired a strategy to enhance their chance of survival and reproduction. Small changes in ambient temperature can have major effects on plant architecture and development, such as the transition from the vegetative to the reproductive flowering phase. The moment of flowering is an important event in the life cycle of a plant, since reproductive success depends on it.

In Chapter 1, I introduced the concept of alternative splicing, a molecular mechanism with a pivotal role in ambient temperature regulation of flowering time. In the model plant Arabidopsis thaliana, approximately 60% of the intron-containing genes show alternative splicing. Gene splicing varies depending on developmental stage and tissue type, but also environmental changes trigger differential splicing. Splicing is conducted by a large cellular machinery called the spliceosome, which recognizes intron-defining sequences and other cis-regulatory elements acting as splicing enhancers or silencers. Moreover, factors like chromatin structure, histone marks, RNA polymerase II (polII) elongation speed and the secondary structure of the pre-mRNA all play a role in the splicing outcome. Due to alternative splicing, a single gene can yield various transcripts. However, this does not cause an equal expansion of the proteome. Part of the transcripts are targeted for nonsense-mediated decay, or will be translated into unstable proteins. This is a way of regulating gene expression at the post-transcriptional or –translational level. Other transcripts will be translated into functional proteins that may be structurally and functionally different. Hence, alternative splicing creates additional complexity in the transcriptome, providing plants with molecular tools to respond to their environment, including the translation of ambient temperature alterations into a flowering time response.
In Chapter 2, we reviewed the current knowledge on molecular mechanisms that control the ambient-temperature directed flowering time pathway in the plant model species Arabidopsis thaliana. Several different mechanisms have been proposed, like alternative splicing of FLOWERING LOCUS M (FLM) (described in Chapter 4) and protein degradation of SHORT VEGETATIVE PHASE (SVP), two mechanisms that probably work in a cooperative manner to release floral repression at higher ambient temperatures. Another mechanism that is involved at high ambient temperature is the replacement of the canonical histone H2A by the variant H2A.Z. As a consequence of this replacement, chromatin becomes less tightly wrapped around the nucleosomes, which allows transcription of flowering time activators, such as PHYTOCHROME INTERACTING FACTOR 4 (PIF4). Lastly, we discuss microRNAs (miRNA) that can either repress or activate flowering (miR156 and miR172, respectively). These miRNAs have been proposed to be regulated by low and high ambient temperature. However, due to the lack of mutant analyses, more research is necessary to show the true involvement of these factors. Altogether, there are several mechanisms acting partly in cooperation to regulate thermosensitive floral timing.
In Chapter 3, we analysed ambient temperature-directed alternative splicing events that occur after a temperature shift by RNAseq. We performed the experiment in two different accessions of A. thaliana, and in one variant of B. oleracea (cauliflower). We showed that flowering time genes are overrepresented amongst the ambient temperature induced alternatively spliced genes, but also genes encoding components of the splicing machinery itself, indicating that alternative splicing is one of the potential mechanisms by which plants are able to sense temperature and adapt floral timing. Analysis of a mutant for one of these alternatively-spliced splicing related factors, ATU2AF65A, showed a temperature-dependent flowering time phenotype, confirming its proposed role in the flowering time response upon temperature fluctuations. Based on these findings, we proposed a two-step model in which splicing related genes are targeted for differential splicing upon ambient temperature fluctuations, which results in changes in the composition of the spliceosome, causing differential splicing of downstream genes that affect the development and architecture of the plant, including flowering time.
In Chapter 4, we investigated the molecular mode-of-action of FLM, one of the differentially spliced flowering time regulating genes that we identified in Chapter 3. We showed that in A. thaliana Col-0, the main splice forms of FLM are FLMβ and FLMδ. FLMβ forms an obligate heterodimer with SVP, and this complex represses floral integrators like SUPPRESSOR OF OVEREXPRESSION OF CONSTANS1 (SOC1) by binding to the regulatory regions of these genes. FLMδ also dimerizes with SVP, but this complex is not able to bind to DNA. When temperature rises, more FLMδ is produced at the cost of FLMβ. Hence, less repressive complexes can be formed. However, the fact that FLMδ is still able to binds SVP makes it function as a dominant negative form, titrating out SVP and preventing repressive SVP/FLMβ-complex formation.
Chapter 5 is a short comment written to clarify the concept of thermoplasticity in flowering time control. Occasionally, this concept is confused with adaptation to different ambient temperature environments on the long term. Thermoplasticity is the ability to adapt flowering time to fluctuations in ambient temperature within one life cycle. Furthermore, some genes have been marked as players in the ambient temperature response, whereas these appear to be general flowering repressors or activators, affecting flowering time in a similar manner at low and high ambient temperature. In order to interpret novel findings on thermosensitive flowering time control, it is essential to distinguish between these various concepts.
In chapter 6, we unveiled the first indications that differential splicing of FLM can be caused by differences in polymerase II elongation rate. We mimicked a situation in which FLM is transcribed at a higher rate, by expressing the genomic FLM gene under a strong artificial promoter. Preliminary results showed that plants harbouring this construct have altered flowering time and temperature-responsiveness, which can be explained by the altered FLMβ/FLMδ ratio that we observed.
In chapter 7, we assessed the functional conservation between FLM and closely related genes at the intraspecific level in A. thaliana. FLM (also called MAF1) is a member of the FLC-clade, that consists of FLC, FLM and MAF2-5. FLC is widely known for its function in the vernalization pathway, whereas MAF2 has been shown to regulate flowering time through alternative splicing in a way very similar to FLM. For the other MAF genes, not much is known. We showed that all of these genes produce splicing isoforms that function in a more or less similar way to FLM and MAF2. Despite the high functional conservation at the intraspecific level, FLM and MAF orthologues are not widely present. Through synteny analysis, we showed that FLM and MAF2 are very recent genes, which are only present in a small group of Brassicaceae species. MAF3-5 originated less recently, but are not present outside the Brassicaceae. For FLC, it was previously shown that it originated from an ancestor of the seed plants, and in many plant species belonging to other families, presence of more than one FLC-like gene has been reported. This raises the question what the function of these genes is. In tomato, we showed that the FLC-like gene MBP8 becomes differentially spliced upon temperature changes, suggesting a function in the ambient temperature pathway. A binding assay showed high similarities of the different MBP8 isoforms to FLM and MAF isoforms, but suggests a slightly different functionality, since all three isoforms showed binding to the DNA. Further research is necessary to confirm the role of MBP8 in thermosensitive flowering time control, and elucidate the functionality of the different splice forms.
In Chapter 8, I discussed the finding of this thesis in a broader perspective, and make suggestions for future research. Over the last few years, several mechanisms that act in the temperature-directed floral pathway have been revealed. In this thesis, we showed that alternative splicing plays an important role, and we demonstrated how temperature may affect the splicing outcome directly through the effect of temperature on transcription elongation rate. It is becoming clear that most likely a single thermosensor does not exist in plants, and a model in which temperature is sensed through thermodynamic properties of DNA, RNA and proteins, is gaining support. Future research is assigned to the exiting task to elucidate the exact mechanisms by which temperature-sensing is achieved in different plant species and to determine how conserved the currently identified molecular mechanisms are.

Plant reageert bij bloei op externe signalen als temperatuur en daglengte : vernalisatie zorgt voor het juiste bloeitijdstip
Heuvelink, E. ; Kierkels, T. - \ 2016
Onder Glas 13 (2016)12. - p. 40 - 41.
temperatuur - fotoperiode - planten - bloei - milieufactoren - temperature - photoperiod - plants - flowering - environmental factors
Een plant die op het punt staat te gaan bloeien, kan zich niet bedenken als de omstandigheden toch tegen blijken te vallen. De overgang naar de bloei is onomkeerbaar. Daarom is het van het grootste belang voor het voortbestaan van de soort dat de bloei precies op het juiste tijdstip valt. Om dat voor elkaar te krijgen, reageert de plant op externe signalen, vooral de temperatuur en de daglengte.
Stress speelt een belangrijke rol : inzicht in koploosheid groeit door gezamenlijk onderzoek
Groot, S.P.C. ; Kierkels, T. ; Heuvelink, E. - \ 2016
Onder Glas 13 (2016)8. - p. 30 - 31.
tuinbouw - groenten - landbouwkundig onderzoek - groeistoornis - plantenontwikkeling - verlichting - tomaten - capsicum - brassica - gypsophila - stresstolerantie - temperatuur - horticulture - vegetables - agricultural research - failure to thrive - plant development - lighting - tomatoes - stress tolerance - temperature

Jonge tomaten- en paprikaplanten, maar ook een aantal andere gewassen, houden soms opeens op met groeien. Koploosheid was lange tijd een lastig maar zeer slecht begrepen fenomeen. De laatste jaren is het inzicht in een stroomversnelling gekomen. In ieder geval is het aantal mogelijke oorzaken drastisch ingeperkt.
Groene daken in Tilburg : ervaringen, motieven en opschalingsmogelijkheden
Hendriks, Kees ; Hommes, Saskia - \ 2016
Wageningen : Wageningen Environmental Research (Wageningen Environmental Research rapport 2767) - 49
groene daken - groene gevels - beplantingen - warmtestress - stedelijke gebieden - welzijn - luchtkwaliteit - temperatuur - regenwateropvang - milieufactoren - openbaar groen - green roofs - green walls - plantations - heat stress - urban areas - well-being - air quality - temperature - water harvesting - environmental factors - public green areas
Green roofs can contribute to climate adaptation and a sustainable urban environment. Whether
municipalities for these or other reasons should encourage green roofs, depends on the goals that are
aimed at. For the municipality of Tilburg opportunities were investigated for usage of green roofs as
measure for climate adaptation and for scaling up green roof in Tilburg and other municipalities. In
three projects in Tilburg the opportunities for the application of green roofs and the attitude of actors
involved were investigated. Also, the experiences of six other municipalities, which are promoting
green roofs, were examined. The type of project, purpose, and insight in costs and benefits affect the
attitude of actors and hence the opportunities for application and scaling. In the examined
municipalities green roofs in general are stimulated with subsidy, communication and pilot projects.
The experience with green roofs in other municipalities are predominantly positive.
Arctic climate change and decadal variability
Linden, Eveline C. van der - \ 2016
University. Promotor(en): Wilco Hazeleger, co-promotor(en): R. Bintanja. - Wageningen : Wageningen University - ISBN 9789462579453 - 197
climatic change - arctic regions - global warming - temperature - models - carbon dioxide - sea water - barents sea - klimaatverandering - arctische gebieden - opwarming van de aarde - temperatuur - modellen - kooldioxide - zeewater - barentszzee

High northern latitudes exhibit enhanced near-surface warming in a climate with increasing greenhouse gases compared to other parts of the globe, indicating an amplified climate response to external forcing. Decadal to multidecadal variability sometimes enhances and at other times reduces the long-term trends. Therefore, the influence of internal variability should be taken into account when externally forced climate signals are assessed.
This thesis contributes to our understanding of Arctic climate projections by clarifying the role of coupled ocean-sea-ice-atmosphere processes on the long-term trends and decadal variability of the Arctic climate system. Important mechanisms linked to the location of the sea ice margin and ocean heat transports into the Arctic have been identified and were shown to have a substantial effect on the Arctic's response to climate change.

Anaerobic treatment of municipal wastewater in a UASB-Digester system : temperature effect on system performance, hydrolysis and methanogenesis
Zhang, Lei - \ 2016
University. Promotor(en): Grietje Zeeman; Huub Rijnaarts, co-promotor(en): Tim Hendrickx. - Wageningen : Wageningen University - ISBN 9789462579798 - 165
municipal wastewater - anaerobic digesters - hydrolysis - temperature - water treatment sludge - sludges - water treatment - sewage sludge - sewage - stedelijk afvalwater - anaërobe verteerders - hydrolyse - temperatuur - waterzuiveringsslib - slib - waterzuivering - rioolslib - rioolwater

A novel treatment chain for low strength domestic sewage includes low temperature anaerobic treatment as the main process. It can improve the energy efficiency of sewage treatment compared with conventional aerobic sewage treatment. A combination of an Upflow Anaerobic Sludge Blanket reactor and a sludge digester, a UASB-digester system, was proven to be one of the successful anaerobic systems to challenge temperatures as low as 10°C and organic matter concentrations in the range of 382 and 1054 mg chemical oxygen demand (COD)/l. The UASB is operated at low sewage temperature (10°C) and high loading rate. The produced non-stabilised sludge in the UASB is recirculated over the mesophilic digester (35°C) to convert organic solids to methane gas and produce anaerobic biomass fed back into the UASB reactor, where it converts dissolved COD at the low temperature of the waste water.

The effect of sludge recirculation rate and sludge transfer point on the performance of a UASB-digester treating domestic sewage at 15 ˚C was studied in this research. The results show increased total COD removal efficiency when increasing the sludge recirculation rate from 1% to 2.6% of the influent flow rate. Methane gas production increases with the sludge recirculation rate, in the range of 1 to 12.5% of the influent flow rate. A higher sludge transfer point results in an increased suspended COD removal efficiency and a higher VSS concentration of the UASB sludge bed.

Co-digestion was applied for improving soluble COD removal efficiency of a UASB-digester system, operated at low temperatures and treating domestic sewage with a high dissolved/suspended COD ratio. Glucose was chosen as a model co-substrate and added to the sludge digester to produce additional methanogenic biomass, which was continuously recycled to inoculate the UASB reactor. Methane production in the UASB reactor almost doubles and soluble COD removal efficiency equals the biodegradability of the influent dissolved COD, due to a twofold increase in methanogenic capacity, when applying co-digestion 16% of influent organic loading rate. Therefore, co-digestion is a suitable approach to support a UASB-digester for treatment of low temperature domestic sewage.

A pilot scale UASB-digester (130 + 50 L) was studied to treat domestic wastewater at temperatures of 10-20°C at an HRT of 6 h in the UASB reactor and 15 h in the digester. The results show a stable COD removal efficiency of 60 ± 4.6% during the operation at 12.5 to 20°C. COD removal efficiency decreases to 51.5 ± 5.5% at 10°C. The decreased COD removal efficiency is attributed to an increased influent COD load, leading to insufficient methanogenic capacity of the UASB reactor at such low temperature. Suspended COD removal efficiency was 76.0 ± 9.1% at 10-20°C. The effluent COD concentration is 90 ± 23 mg/L at temperatures between 12.5 and 20°C, while soluble COD removal efficiency fluctuates due to variation in the influent COD concentration. 80% of the influent biodegradable COD is recovered as methane gas (including dissolved methane).

Low temperature (10-25°C) hydrolysis after applying a short pre-hydrolysis at 35°C was studied compared with those without the pre-hydrolysis. Batch experiments were executed using cellulose and tributyrin as model substrates for carbohydrates and lipids. Low temperature anaerobic hydrolysis rate constants increase by a factor 1.5 - 10 after applying a short anaerobic pre-hydrolysis at 35°C. The hydrolytic activity of the supernatant collected from the digestate after batch digestion of cellulose and tributyrin at 35°C was higher than that of the supernatants collected from the low temperature (≤ 25°C) digestates. The observed hydrolysis in the UASB of a UASB-digester system, treating domestic sewage at low temperatures (10-20°C) is in line with the elevated hydrolytic activity of mesophilic supernatant.

Effects of temperature and temperature shocks on specific methanogenic activity (SMA), and acetate affinity of the digester sludge were studied. Digester sludge from a UASB (12.5°C)-digester (35°C) system, was fed with acetate at constant temperatures of 10-35°C and at varying temperatures from 35°C to 25, to 15 to 10°C. The results show no lag phase in methane production rate when applying temperature shocks of 35°C to 25, 15, and 10°C. The temperature dependency of the SMA of the digester sludge after the temperature shocks was similar to the one at constant temperatures. Acetate affinity of the digester sludge was high at the applied temperatures (10-35°C). Latter is consistent with the finding of no VFA in the effluent of the UASB-digester, treating low strength, and low temperature (12.5°C) domestic wastewater.

The UASB-digester system to treat low strength, low temperature domestic sewage was provided with a proof-of-principle, and its essential underlying anaerobic processes were sufficiently elucidated to make the technology ready for further scaling up and demonstration in practice.

Refining a model-based assessment strategy to estimate the ammonia emission from floors in dairy cow houses
Snoek, Dennis J.W. - \ 2016
University. Promotor(en): Peter Groot Koerkamp, co-promotor(en): Nico Ogink; Hans Stigter. - Wageningen : Wageningen University - ISBN 9789462578852 - 182
dairy cows - stalls - ammonia emission - floors - modeling - mitigation - sensors - ph - temperature - urea - melkkoeien - stallen - ammoniakemissie - vloeren - modelleren - mitigatie - temperatuur - ureum

Ammonia (NH3) emission is still high, and agriculture is still the dominant contributor. In The Netherlands, the NH3 emission from dairy cow houses is one of the most important sources. A lot of research has been conducted to understand and model NH3 emission, to measure it, and to reduce it using identified and developed reduction measures. However, our understanding of how to measure and how to reduce the NH3 emission is still limited. In addition, the set emission ceilings were lowered for 2020.

The objective of this thesis was to refine a model-based assessment strategy to estimate the ammonia emission from floors in dairy cow houses. First the most important input variables and process parameters were identified with a sensitivity analysis in currently available mechanistic NH3 emission models and theory. It was concluded that five puddle related input variables caused the largest variation in NH3 emission estimation, being the puddle pH, depth (Dp), urinary urea nitrogen concentration (UUN), surface area (Ap), and temperature (Tliq). For each input variable the available data was scarce, and it was therefore recommended to measure these five most important variables in practice. However, measurement methods were hardly available. Therefore, sensors were chosen, new measurement methods were developed, and these were combined in a protocol to measure the pH, Dp, UUN, Ap and Tliq of fresh, random and manually created urine puddles in commercial dairy cow houses.

In total 16 commercial dairy cow houses were assessed in a factorial experimental setup based on four floor-management types in two Seasons, with PREclean treatment. PREclean represented intense-floor-cleaning that was compared to on-farm manure scraping. A V-shaped asphalt floor had significantly larger values for both Ap (1.04 m2) and Dp (1.5 mm) than did the slatted and grooved floors (0.76 m2, 0.93 mm). For both Ap and Dp the variation within a farm was large, but was negligible between farms. The Dp values and variation were 3 to 6 times larger than currently assumed. With PREclean treatment the Dp resulted in about 3 times lower values compared to the on-farm scraping. In short, the potential NH3 emission reduction of good floor cleaning is large. Overall mean values were 4.27 kg m-3 for UUN, an initial pH(t=0) of 8.3, both in fresh puddles, and a pH(t=ξ) of 9.0 for random puddles at a random time. For UUN both the variation within and between farms was large, whereas the variation for pH was small. Both the mean UUN and pH showed lower values than currently assumed. In a separate 4 h time series experiment at 3 commercial farms was shown that the pH, on average, quickly increased initially, declined after 1 h and then became stable. The calculated NH3 in kg puddle-1 showed a huge range and was considerably larger than currently assumed for the reference situation.

Compared to the aforementioned sensitivity analysis outcome, the UUN range at farm level is both slightly smaller and shifts to slightly lower values, while for Dp the range and values are both larger. These two variables caused the largest variation in the estimated NH3 emissions, and not the pH. In conclusion, these two variables certainly need to be measured in individual commercial dairy cow houses to estimate the NH3 emission. For Ap, pH and Tair the measured ranges at farm level were less large. The pH turns out to be fairly stable in commercial cow houses and, related to that, it causes less variation in the estimated NH3 emission. Nevertheless, the pH still ranks as the third most important variable, and therefore needs to be measured in individual cow houses. The Ap is fairly stable between farms, but varies within farms and it still has a significant effect on the NH3 emission. The floor design clearly affects the puddle area Ap. Therefore, it is not necessary to measure Ap at each individual farm, but it is sufficient to measure the Ap in only one commercial cow house per floor design. The Tair variable is of limited importance compared to the aforementioned four variables, but it is still significant.

Literatuurstudie watertemperatuur en glasaaluitzetting
Schram, Edward ; Graaf, Martin de - \ 2016
IJmuiden : Wageningen Marine Research (Wageningen Marine Research rapport C086/16) - 20
palingen - temperatuur - watertemperatuur - eels - temperature - water temperature
De doelen van deze studie zijn: - Het verkrijgen van inzicht in de richtlijnen voor de watertemperatuur in de protocollen voor het uitzetten van glasaal in andere Europese landen; - Nagaan of er sinds 2009 nieuwe onderzoeksresultaten zijn gepubliceerd in de wetenschappelijke literatuur die relevant zijn voor temperatuurrichtlijnen voor het uitzetten van glasaal in het buitenwater.
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