Root and nodule : lateral organ development in N2-fixing plants
Xiao, T.T. - \ 2015
Wageningen University. Promotor(en): Ton Bisseling, co-promotor(en): Rene Geurts; Henk Franssen. - Wageningen : Wageningen University - ISBN 9789462572768 - 198
medicago - wortelknolletjes - endosymbiose - symbiose - mycorrhizae - stikstoffixatie - plantenontwikkeling - moleculaire biologie - medicago - root nodules - endosymbiosis - symbiosis - mycorrhizas - nitrogen fixation - plant development - molecular biology
Plants are sessile organisms. This characteristic severely limits their ability of approaching nutrients. To cope with this issue, plants evolved endosymbiotic relationships with soil fungi to extend their interface with surrounding environment. In case of arbuscular mycorrhizae (AM) fungi this occurred about 400 million years ago. The AM fungi can interact with most angiosperms. In this symbiotic relationship, the plant get nutrients, especially phosphate, from the fungi, and plants provide carbohydrates to the fungi in return. About 60 million years ago, a group of plants evolved N2-fixing nodule symbiosis. This includes interactions of legumes plants with rhizobium bacteria and actinorhizal plants with Frankia bacteria. Currently, all plant species that are able to establish a nodule symbiosis belong to the Rosid I clade. In the nodule symbioses the bacteria produce ammonia and the plant provides carbohydrates to the bacteria.
In the root nodule symbiosis, the nitrogen fixing bacteria are hosted in the cell of the root nodule. Although the function and structure of the root nodule are different from the other plant organs, it does share some features with other organs, especially the lateral root. To get further insight into the similarities and differences between root nodule and lateral root, I made use of the model legume (Medicago truncatula) and the non-legume Parasponia (Parasponia andersonii) that is the only genus outside the legumes that forms nodules with rhizobium.
In Chapter 1, I will give a general introduction on the process of root nodule formation in legume plants. I will mainly focus on nodule organogenesis and the plant hormones that are known to be important for this process. Root nodules are supposed to have a close relationship with lateral roots. Therefore a comparison between lateral root and root nodule development will be included in this introduction.
Lateral root development has especially been studied in in Arabidopsis. To be able to compare the root and root nodule developmental process, especially at the early stages, a Medicago lateral root development fate map has been made. This will be described in Chapter 2 and showed that in addition to the pericycle, endodermis and cortex are also mitotically activated during lateral root formation. Pericycle derived cells only form part of the stem cell niche as endodermis derived cells also contribute to this.
In Chapter 3, a Medicago root nodule fate map is presented. In this Chapter, the contribution of different root cell layers to the mature nodule will be described. A set of molecular markers for root tissue, cell cycle and rhizobial infection have been used to facilitate this analysis. The fate map showed that nodule meristem originates from the third cortical layer and many cell layers of the base of the nodule are directly derived from cells of the inner cortical layers, root endodermis and pericycle. The inner cortical cell layers form about 8 cell layers of infected cells while the root endodermis and pericycle derived cells forms the uninfected tissues that are located at the base of the mature nodule. Nodule vascular is formed from the part of the primordium derived from the cortex. The development of primordia was divided in 6 stages. To illustrate the value of this fate map, a few published mutant nodule phenotypes are re-analyzed.
In Chapter 4, the role of auxin at early stages of Medicago nodule formation is studied. In this chapter auxin accumulation is studied during the 6 stages of primordium development. It is studied by using DR5::GUS as an auxin reporter. Auxin accumulation associates with mitotic activity within the primordium. Previously, it has been postulated by theoretical modelling that the accumulation of auxin during nodulation is induced by a local reduction of PIN (auxin efflux carriers) levels. We tested this theory, but this was hampered due to the low level of PIN proteins in the susceptible zone of the root. It is still possible that auxin accumulation is initiated by a decrease of PIN levels. However, the level of 2 PIN already increase before the first divisions are induced. In young primordia they accumulate in all cells. At later stages PINs mainly accumulate at the nodule periphery and the future nodule meristem. The subcellular position of PINs strongly indicates they play a key role in the accumulation of auxin in primordia.
Previous studies showed that a group of root apical meristem regulators is expressed in the nodule meristem. In Chapter 5, we tested whether the Medicago nodule meristem expresses PLETHORA genes that are expressed in the root meristem. These PLETHORAs were functionally analysed, by using RNAi approach using a nodule specific promoter. Knockdown of PLETHORAs expression hampers primordium formation and meristem growth. Hence, we conclude rhizobium recruited key regulators of root development for nodule development.
In Chapter 6, we first introduced the non-legume lateral root and nodule fate maps by using Parasponia. In Parasponia nodules the nodule central vascular bundle is completely derived from the pericycle similar as its lateral roots. The nodule infected cells were shown to be derived from cortex. Together with the data obtained in this thesis, this Chapter further discussed several developmental aspects of the different lateral root organs. Especially, it focused on the vasculature and meristem formation of legume and non-legume nodules.
Soil and plant responses to pyrogenic organic matter: carbon stability and symbiotic patterns
Sagrilo, E. - \ 2014
Wageningen University. Promotor(en): Thomas Kuijper; Ellis Hoffland. - Wageningen : Wageningen University - ISBN 9789462571679 - 128
organisch bodemmateriaal - grondverbeteraars - koolstofvastlegging in de bodem - vesiculair-arbusculaire mycorrhizae - bodemvruchtbaarheid - glycine max - biochar - stikstoffixatie - kooldioxide - emissie - brazilië - soil organic matter - soil amendments - soil carbon sequestration - vesicular arbuscular mycorrhizas - soil fertility - glycine max - biochar - nitrogen fixation - carbon dioxide - emission - brazil
Soil and plant responses to pyrogenic organic matter: carbon stability and symbiotic patterns
Pyrogenic organic matter (PyOM), also known as biochar, is the product of biomass combustion under low oxygen concentration. There is currently a growing interest in research on the use of PyOM as a soil amendment, inspired by the existence of highly fertile, PyOM-rich anthropogenic soils in the Amazon basin. The presence of PyOM in these so-called Amazonian Dark Earths (ADE) in quantities larger than in the non-anthropogenic surrounding soils is considered one of the main reasons for their high fertility.
Soil additions of PyOM have been suggested to increase soil fertility and crop yields, simultaneously providing additional important environmental services. The offset of CO2 emissions through sequestration of a larger pool of recalcitrant soil organic carbon (SOC) is one of these services. This would at the same time sustain soil microbial activity, which is directly associated to soil quality, for instance, nutrient cycles and plant growth. This multiple win scenario suggests that the addition of PyOM to the soil would be the solution for the “carbon dilemma”. The dilemma states that the main biological benefits from soil organic matter are a consequence of its decay. Therefore, it is unlikely that increased C sequestration and the benefits from its decay can be simultaneously maximized. Rather than win-win, PyOM would then also be subjected to inevitable trade-offs.
Additions of PyOM can modify the turnover rate of native SOC by either accelerating or decelerating its decomposition through a mechanism known as priming. Although positive priming by PyOM has been reported, negative priming has also been found. The higher amount of non-pyrogenic C in ADE, compared to non-anthropogenic surrounding soils has been considered evidence that PyOM can stabilize SOC in the long-term. A complicating issue in studies is that short-term increases in CO2 emission can be due to decomposition of labile PyOM fractions, erroneously suggesting positive priming of SOC. Addition of PyOM can also lead to modifications in the microbial activity and assemblages. Changes in microbial populations can have impacts on their functionality, favouring mutualistic root symbioses such as the arbuscular mycorrhizal fungal (AMF) symbiosis and the rhizobial symbiosis with legumes that is responsible for biological nitrogen fixation (BNF). Although soil amendments with PyOM can stimulate AMF and BNF, results are contrasting and mechanisms are not clear. Most studies of PyOM effects on SOC and on mutualistic root symbioses are from short-term experiments, often conducted in greenhouse or laboratory. Although such studies provide insights in potential factors driving changes in SOC and symbiotic relationships in PyOM-amended soils, they do not assess changes under realistic conditions over periods of time longer that one or a few cropping cycles. Therefore, there is still a gap in our understanding regarding the duration and magnitude of effects over time under field conditions and possible mechanisms involved. This thesis addresses these gaps.
The aim of this research was to provide a better understanding of interactions between PyOM and SOC and the factors controlling symbiotic patterns in a tropical soil amended with PyOM. To reach this aim, I combined greenhouse and field studies. I also used meta-analytic methods in order to quantitatively synthesize data in literature.
In Chapter 2, I combined the results of 46 studies in a meta-analysis. I investigated changes in CO2 emission patterns from an array of PyOM-amended soils and identified the causes of these changes and the possible factors involved. I showed an overall increase of 29% in CO2 emission from PyOM-amended soils. Such increases were only evident in soils amended with a PyOM-C (PyC):SOC ratio >2. These data are consistent with the hypothesis that increased CO2 emission after PyOM addition is additive and mainly derived from PyOM’s labile C fractions rather than from SOC. Therefore, positive priming is not a main driver of increases in CO2 emission in PyOM-amended soils. This PyC:SOC ratio provided the best predictor of increases in CO2 production after PyOM addition to soil. This meta-analysis indicates (i) the importance of taking into account the amount of applied PyC in relation to SOC for designing future decomposition experiments and that (ii) the recalcitrance of PyOM in soil-PyOM mixtures may be less than usually assumed.
A technical problem of separating PyOM-induced priming on SOC from other non-additive interactions is the uncertainty regarding the origin of the respired CO2 (whether from SOC or PyOM). This issue can only be solved with the use of isotopes. In a field study (Chapter 3), I quantified changes in the PyOM and SOC stocks over four soybean cropping cycles (CC) in a sandy Ferralsol, previously supporting a vegetation with C4 plants, amended with different rates of PyOM (0, 5, 10, 20 and 40 Mg ha-1). The PyOM was produced from C3 woody species using traditional pyrolysis methods employed in Northeast Brazil. I used 13C isotopic analysis to discriminate the origin of the C in the soil and quantify the decomposition rates of native SOC and PyOM. I showed that decomposition of traditionally produced PyOM is faster (25-60% within first year) than normally assumed (10-20% within 5-10 years), which was higher than that of native SOC (5-14%). The data indicate preferential decomposition of PyOM compared to native SOC. The intensity of that effect depends on the rate of PyOM applied to the soil. Only on the longer term (>1 yr) addition of PyOM seems to stabilize SOC.
In Chapter 4 I explored mechanisms controlling AMF activity and crop yield in PyOM-amended soils through the use of path analysis. I tested the effects of PyOM rates and P fertilization on soybean root colonization by AMF, soil P and plant performance over four cropping cycles (CCs). Data showed a major effect of CC and P, as well an interaction effect of PyOM x CC on mycorrhizal colonization. There was a linear decrease in root colonization by AMF in CC1 with increasing PyOM rates in contrast to a consistent linear increase in CC4. Plant performance was mainly affected by CC, but a significant interactive effect of PyOM x P was also observed on grain yield. Grain yield was highest at high PyOM rates (20 and 40 Mg ha-1) in the P-fertilized treatments in CC4. Soil pH increased in CC1 with increasing PyOM rates, but no effects were observed in CC4. Path analysis indicated that PyOM effects on root colonization by AMF were not mediated by changes in soil pH or P content. My data are consistent with the hypothesis that interference of PyOM in signalling processes is an important driver of change in AMF activity and that positive effects of PyOM on AMF and crop yield develop with time.
In Chapter 5, I assessed the effects of PyOM application rates and P fertilization on BNF in soybean inoculated with Bradyrhizobium japonicum over four cropping cycles. Again I observed that CC had a significant main effect on most dependent variables, while PyOM was not a significant source of variation. There was a significant PyOM × CC interaction effect on shoot N concentration. In CC1 shoot N concentration after application of 5 Mg PyOM was significantly lower than that of plants grown on plots to which 10 or 20 Mg PyOM was applied. In CC4 shoot N concentration was not affected by PyOM. The major effect of CC was explained through changes in nutrient management, more specifically the addition of micronutrients in CC3 and CC4. Alleviation of micronutrient deficiency increased BNF and also resulted in a positive effect of P on BNF. I conclude that under conditions of adequate management, PyOM application does not improve BNF in soybean.
In Chapter 6 (General Discussion) I synthesize the findings of the previous chapters and use data from additional greenhouse and litterbag field experiments to integrate the results. Data from Chapters 2 and 3 show that if any positive priming occurs due to PyOM addition, it is a small short-term event and does not lead to significant losses of native SOC in the long-term. This was confirmed by data from a 2 yr litterbag experiment, which showed no interaction between decomposition of PyOM and fresh organic matter.
Stability of SOC has been considered an ecosystem property rather than a consequence of recalcitrance, but this definition has not yet been extended to PyOM. In this thesis I demonstrated that stability of PyOM can also be influenced by the soil environment. In order to link PyOM effects to SOC and on root symbioses, I performed path analysis integrating root colonization by AMF, SOC content and Ndfa in one model. We found no significant path coefficients linking AMF and BNF. The model indicated a significant positive path coefficient linking AMF root colonization and SOC in CC4, but not in CC1. The data suggest that PyOM may increase SOC stability through increased AMF activity. Soil aggregation and C sequestration are tightly correlated with abundance of AMF in the soil. I propose that the same mechanism through which AMF stabilizes native SOC may also positively influence PyOM stabilization in the long-term.
In conclusion, I have shown that main beneficial effects of PyOM on AMF and crop yield develop with time, but in well-managed soils increased crop yield is not a direct consequence of increased AMF due to PyOM addition. Finally, although PyOM additions represent an effective form of sequestering C, positive effects of PyOM on crop yield are likely to occur after partial decomposition of PyOM. Therefore, although some benefits of adding PyOM can be simultaneously obtained (C sequestration and increased crop yield), they cannot be simultaneously maximized. This means that the carbon dilemma can only be partially solved by adding PyOM to the soil.
Transcriptional regulation of nodule development and senescence in Medicago truncatula
Karmarkar, V.M. - \ 2014
Wageningen University. Promotor(en): Ton Bisseling, co-promotor(en): Rene Geurts. - Wageningen : Wageningen University - ISBN 9789462570214 - 110
medicago truncatula - plantenontwikkeling - veroudering - wortelknolletjes - stikstoffixatie - genexpressie - symbiose - transcriptie - transcriptiefactoren - medicago truncatula - plant development - senescence - root nodules - nitrogen fixation - gene expression - symbiosis - transcription - transcription factors
Comparative and functional analysis of NODULATION SIGNALING PATHWAY 1 (NSP1) and NSP2 in rice and Medicago
Liu, W. - \ 2013
Wageningen University. Promotor(en): Ton Bisseling, co-promotor(en): Rene Geurts. - S.l. : s.n. - ISBN 9789461736369 - 147
oryza - medicago - knobbelvorming - symbiose - genen - rhizobium - wortelknolletjes - stikstoffixatie - oryza - medicago - nodulation - symbiosis - genes - rhizobium - root nodules - nitrogen fixation
The formation of endosymbiotic membrane compartments: membrane identity markers and the regulation of vesicle trafficking
Ivanov, S. - \ 2012
Wageningen University. Promotor(en): Ton Bisseling, co-promotor(en): Elena Fedorova; Erik Limpens. - S.l. : s.n. - ISBN 9789461733436 - 121
planten - rhizobium - stikstof - stikstoffixatie - medicago - endosymbiose - celmembranen - blaasjes - biochemische omzettingen - moleculaire biologie - wortels - mycorrhizae - plants - rhizobium - nitrogen - nitrogen fixation - medicago - endosymbiosis - cell membranes - vesicles - biochemical pathways - molecular biology - roots - mycorrhizas
In symbiosis of plants and arbuscular mycorrhizal fungi as well as in rhizobium-legume symbiosis the microbes are hosted intracellularly, inside specialized membrane compartments of the host. These membrane compartments are morphologically different but similar in function, since they control the exchange of compounds between host and its microsymbiont thus forming a highly specialized symbiotic interface. These are the arbuscules, containing highly branched fungal hyphae, and organelle-like symbiosomes containing rhizobium bacteria. Recent studies have markedly extended our insight in the evolution of the signaling mechanism underlying the formation of these symbiotic interfaces. These studies strongly suggest that rhizobium co-opted the complete signaling mechanism (including lipo-oligosaccharides signal molecules) from the more ancient AM fungi symbiosis. Further, in plant species (Parasponia) where rhizobium nodulation evolved rather recent and independent from legumes, the same lipo-oligosaccharide receptor is essential for the formation of the rhizobium symbiotic interface as well as arbuscules. Therefore it seems likely that rhizobium also co-opted the cellular mechanism controlling arbuscule formation to form a rhizobium symbiotic interface. This would imply that even after co-evolution in legumes the key regulators involved in the formation of these interfaces are similar or even identical.
Co-option of pre-existing pathways during Rhizobium-legume symbiosis evolution
Lillo, A. - \ 2012
Wageningen University. Promotor(en): Ton Bisseling, co-promotor(en): Rene Geurts. - S.l. : s.n. - ISBN 9789461733443 - 151
rhizobium - fabaceae - symbiose - evolutie - stikstoffixatie - wortels - fylogenetica - genomen - medicago - eerste wortels - rhizobium - fabaceae - symbiosis - evolution - nitrogen fixation - roots - phylogenetics - genomes - medicago - root primordia
Fixed nitrogen is one of the most limiting factors for plant growth. One of the most important nitrogen-fixing systems is the rhizobium root nodule symbiosis. In this Thesis I have studied the legume-rhizobium symbiosis, starting from the idea that part of pre-existing signalling pathways have been co-opted during evolution of this mutualistic interaction. Gene duplications -of which a whole genome duplication (WGD) is the most dramatic variant- are known as important driving forces in evolution of new traits. 56 to 65 million years ago an ancestral legume species within the Papilionoidae subfamily (Papilionoids) experienced a WGD event and subsequently gave rise to several major phylogenetic crowns. I hypothesize that among the orthologous gene pairs maintained are genes that are essential for nodulation. I adopted a phylogenetic strategy to identify new candidate genes involved in the legume-Rhizobium symbiosis
Problems and opportunities of wetland management in Rwanda
Nabahungu, N.L. - \ 2012
Wageningen University. Promotor(en): Leo Stroosnijder, co-promotor(en): Saskia Visser. - S.l. : s.n. - ISBN 9789085859246 - 134
wetlands - landbouw - landbouw bedrijven - gewasproductie - voedingsstoffen - stikstoffixatie - middelen van bestaan - rwanda - wetlands - agriculture - farming - crop production - nutrients - nitrogen fixation - livelihoods - rwanda
The aim of this research was to identify problems and opportunities regarding management of wetlands in Rwanda, with a focus on their agricultural use. In Rwanda cultivated wetlands cover 148,344 ha and they play an important role in supporting farmers’ livelihood through agriculture. This thesis reveals the extent to which degradation of wetlands negatively affects individuals, households, communities, the national economy and even potentially the greater hydrology of a region. Cyabayaga and Rugeramigozi wetlands were selected as representatives for agricultural wetlands. The rice in Cyabayaga was the largest contributor to household income with $ 1045 per household per season whereas vegetables cultivated in the dry season in Rugeramigozi have high potential as cash crops. Nutrient balances in wetland fields are influenced by agricultural potential, farming system, access to resources, gross margin, size of livestock herd and farmers resource endowment. The marketability of the crops is critical factor in the decision to invest in soil fertility improvement. Legumes and maize yields were lowest on the hillside plots compared to wetlands. Fertilizer application increased grain yield of both legumes and maize and nitrogen fixation, the highest yield was observed in the treatment combining organic and inorganic fertilizers. Maize yield after legume was higher than continuous maize production. The nitrogen balance was negative in both sites at all landscape positions. Findings of this study stress the need of integrated watershed management for improved wetland management.
De kracht van de stikstofbinders
Giller, K.E. ; Bisseling, T. - \ 2012
WageningenWorld 2012 (2012)1. - ISSN 2210-7908 - p. 30 - 37.
peulgewassen - stikstoffixatie - wortelknolletjes - stikstofbindende bacteriën - rhizobium - veldgewassen - afrika - legumes - nitrogen fixation - root nodules - nitrogen fixing bacteria - rhizobium - field crops - africa
Hoogleraar Ken Giller propageert onder Afrikaanse boeren het gebruik van peulvruchten. Die hebben dankzij hulp van bacteriën geen stikstofmeststof nodig. In Wageningen onderzoekt hoogleraar Ton Bisseling de finesses van deze symbiose.
Vlinderbloemigen brengen bemesting in evenwicht
Holwerda, J. ; Wel, C. van der; Sukkel, W. - \ 2008
Wageningen : Wageningen UR (BioKennis Bericht : Akkerbouw en vollegrondsgroente ) - 4
biologische landbouw - bodemvruchtbaarheid - organische stikstof - stikstoffixatie - peulgewassen - luzerne - rotaties - groenbemesters - grasklaver - vollegrondsteelt - organic farming - soil fertility - organic nitrogen - nitrogen fixation - legumes - lucerne - rotations - green manures - grass-clover swards - outdoor cropping
Vlinderbloemigen vormen de stikstofbron voor de biologische landbouw. Dit omdat ze in staat zijn stikstof uit de lucht te binden. Voor een duurzame biologische akkerbouw en de groenteteelt zijn ze daarom onontbeerlijk, evenals voor de veehouderij. Uiteindelijk is ook de stikstof uit dierlijke mest in eerste instantie via vlinderbloemigen gebonden.
Exploring socio-ecological niches for legumes in western Kenya smallholder farming systems
Ojiem, J.O. - \ 2006
Wageningen University. Promotor(en): Ken Giller, co-promotor(en): Nico de Ridder; B. Vanlauwe. - [S.l.] : S.n. - ISBN 9789085045137 - 169
peulgewassen - aanpassingsvermogen - biofysica - sociale economie - kenya - heterogeniteit - economische analyse - stikstoffixatie - productiviteit - agro-ecosystemen - legumes - adaptability - biophysics - socioeconomics - kenya - heterogeneity - economic analysis - nitrogen fixation - productivity - agroecosystems
Keywords: adaptability, agro-ecosystems, biophysical and socio-economic heterogeneity, economic benefits, N2-fixation, productivity.This thesis explores the potential of using herbaceous and grain legume species to improve soil fertility and farm productivity in the heterogeneous smallholder farming systems of western
Onderzoek vruchtwisseling: geen bemesting snijmaïs na scheuren van gras-klaver
Boer, H.C. de - \ 2005
V-focus 2 (2005)dec. - ISSN 1574-1575 - p. 30 - 31.
maïs - zea mays - graslandbeheer - klavers - zaadmengsels - stikstoffixatie - mineralisatie - bodemkwaliteit - bemesting - maize - zea mays - grassland management - clovers - seed mixtures - nitrogen fixation - mineralization - soil quality - fertilizer application
In 2002 is op het biologisch praktijkcentrum Aver Heino onderzoek gestart naar de effecten van gras-klaver in vruchtwisseling en snijmaïs in continuteelt op de stikstofbenutting en bodemkwaliteit. Het onderzoek loopt naar verwachting tot 2012 en wordt gefinancierd uit het LNV-programma '100 procent biologische mest'.
Uitwisselen van teelten helpt kwekers verder : biologische teelt
Pronk, A.A. ; Reuler, H. van - \ 2004
De Boomkwekerij 17 (2004)9. - ISSN 0923-2443 - p. 12 - 13.
houtachtige planten als sierplanten - nematoda - stikstoffixatie - uitspoelen - teeltsystemen - tagetes - gewasbescherming - biologische landbouw - ornamental woody plants - nematoda - nitrogen fixation - leaching - cropping systems - tagetes - plant protection - organic farming
Beschrijving van ontwikkelingen in de biologische teelt van boomkwekerijgewassen. Genoemd worden: biologische bestrijding van aaltjes met tagetes; tussengewas als vanggewas om uitspoelen van stikstof te voorkomen
Adapting to change in banana-based farming systems of northwest Tanzania: the potential role of herbaceous legumes
Baijukya, F.P. - \ 2004
Wageningen University. Promotor(en): Ken Giller, co-promotor(en): Nico de Ridder. - Wageningen : Wageningen University - ISBN 9789085040941 - 192
musa - bananen - fabaceae - peulgewassen - zea mays - maïs - stikstoffixatie - landbouwplantenteelt - musa - bananas - fabaceae - legumes - zea mays - maize - nitrogen fixation - crop husbandry
Keywords: Land use changes; Herbaceous legumes; Adoptability; N 2 -fixation; Residual effect; Legume management; Exploration of options, Nutrient depleted soils.The banana-based farming system in
Nitrogen Cycling in Agroforestry Systems of Sub-humid Zimbabwe: Closing the loop
Chikowo, R. - \ 2004
Wageningen University. Promotor(en): Ken Giller, co-promotor(en): Peter Leffelaar; P. Mapfumo. - Wageningen : S.n. - ISBN 9789058089861 - 116
agroforestrysystemen - stikstofkringloop - braaksystemen - verbeterde braak - stikstoffixatie - uitspoelen - mineralisatie - stikstof - zimbabwe - agro-ecosystemen - agroforestry systems - nitrogen cycle - fallow systems - improved fallow - nitrogen fixation - leaching - mineralization - nitrogen - zimbabwe - agroecosystems
Keywords: improved fallows, biological N 2 -fixation, nitrogen cycling, nitrate leaching, oxide emissions, N mineralization -immobilization, granitic sandsThis thesis focuses on nitrogen: its acquisition in cropping systems through biological N 2 -fixation and subsoil capture, its release by legume prunings and litter, its use by maize and its loss through leaching and as nitrous oxide gas. The context of the study is improved fallows using leguminous trees/shrubs on a sandy clay loam soil under sub-humid conditions in
Two-year legume fallows of Sesbania Sesban, Acacia angustissima and Cajanuscajan were evaluated for their residual N effects on two subsequent maize crops under minimum and conventional tillage management. The proportion of N 2 -fixed in litter was 56, 55, 84 and 58 % for Acacia, Sesbania , Cajanus, and cowpea, respectively, resulting in inputs of biologically fixed N of 122, 84, 97 and 28 kg N ha -1 . Maize growth following the legumes for two subsequent cropping seasons was in most cases not directly related to the N inputs due to pest infestation and drought. On a sandy soil, these legumes adapted poorly and did not improve N cycling.
Soil samples for mineral N determination in profiles were taken at fallow termination and every two weeks during maize cropping with an auger in 0.2 m sections to 1.2 m depth. Pre-season NH 4+ amounts were > 12 kg N ha -1 in the 0-0.2 m layer for treatments that had a large litter layer. There was a flush of NO 3- -N in the Sesbania and Acacia plots with the first rains. Topsoil NO 3- had increased to >29 kg N ha -1 by the time of establishing the maize crop. NO 3- -N amounts decreased rapidly within three weeks of maize planting to 9 and 11 kg N ha -1 for the Sesbania and Acacia plots, respectively. Total NO 3- -N leaching losses from the 0-0.4mlayer ranged from 29-40 kg ha -1 for Sesbania and Acacia plots within two weeks when 104 mm rainfall was received to an already fully recharged soil profile. NO 3- -N then increased below the 0.4 m depth during early season when the maize had not developed a sufficient root length density to effectively capture nutrients. Nitrous oxide emissions were small, with a peak of 12 g N 2 O-N ha -1 day -1 from Sesbania plots and near background fluxes in maize monoculture plots. The decrease of mineral N concentration in the topsoil resulted in reduced N 2 O fluxes, despite very high soil moisture conditions. N 2 O-N emissions were greatest for Sesbania plots with only 0.3 kg ha -1 lost in 56 days.
The effects of improved fallows on rainfall partitioning and associated soil loss were investigated using simulated rainfall at 35 mm h -1 . Immediately after fallow clearance, infiltration rates were greater than water application rate for the Acacia and natural fallow treatments, but steady state infiltration rates were 24 mm h -1 in Sesban and 5 mm h -1 in continuous maize. The estimated runoff losses after 30 minutes of rainfall were 44% from continuous maize compared with 22% from Sesbania and none from Acacia and natural fallow plots. After one post-fallow crop, water infiltration was still greater than 35 mm h -1 in the Acacia plots. Steady state infiltration rates after 30 minutes of rainfall were 8 and 5 mm h -1 for Sesbania and continuous maize systems, respectively. Planted tree fallows increase infiltration rates, but the effect markedly decrease after one year of maize cropping in non-coppicing tree fallows.
In a field litterbag decomposition experiment, the course of the decomposition could be adequately described by the function Y = (Y0-Q)e -kt + Q, and the relative decomposition constants for Sesbania and Acacia litters were 0.053 and 0.039 d -1 , respectively. Under laboratory incubation conditions, N mineralized from fresh Sesbania prunings was 55% after 120 days compared with 27% only for the Sesbania litter. During the same period, fresh prunings of Acacia released only 12 % of the added N while Acacia litter released 9 %. N mineralization from Acacia fresh prunings was depressed by the high protein binding capacity of its polyphenols. Except for Sesbania litter, the rest of the senesced legume materials showed N immobilization up to 60 days.
The study showed that Sesbania, Acacia and Cajanus produced useful amounts of biomass on soils of at least loamy texture and improved N cycling significantly, but adapted poorly in lighter soils. Under conditions of severe texture constraints, mucuna showed robustness but has the disadvantage of having no direct food value. Gaseous N losses after incorporating legume materials were small, and the reduction of NO 3- leaching is the single largest challenge to increased N recovery in the highly porous soils.
Vanggewas voor snijmais: Oogsten of niet?
Laarhoven, G.C.P.M. van - \ 2003
Praktijkkompas. Rundvee 17 (2003)2. - ISSN 1570-8586 - p. 12 - 13.
teeltsystemen - tussenteelt - onderteelt - ondergewassen - maïs - rotaties - tussengewassen (intercrops) - oogsttijdstip - zaaitijd - oogsten - zaaien - opbrengsten - gewasopbrengst - stikstof - plantenvoeding - stikstoffixatie - proeven - experimenteel veldonderzoek - cropping systems - intercropping - catch cropping - catch crops - maize - rotations - intercrops - harvesting date - sowing date - harvesting - sowing - yields - crop yield - nitrogen - plant nutrition - nitrogen fixation - trials - field experimentation
Proefbedrijf Cranendonck voerde in de periode 1999 - 2001 een veldproef uit waarin vanggewassen op verschillende tijdstippen zijn gescheurd.
The Nifl PAS domain: Insight into its structure and function
Hefti, M.H. - \ 2003
Wageningen University. Promotor(en): Sacco de Vries, co-promotor(en): Jacques Vervoort. - [S.I.] : S.n. - ISBN 9789058088093 - 116
stikstoffixatie - azotobacter vinelandii - chemische structuur - nitrogen fixation - azotobacter vinelandii - chemical structure
Azotobacter vinelandii is an aerobic soil-dwelling organism with a wide variety of metabolic capabilities which include the ability to fix atmospheric nitrogen by converting it to ammonia. The biosynthesis of ammonia is controlled by 15 to 20 different nif gene products. The activation of nif gene expression by the regulatory enhancer binding protein NifA is controlled by the sensor flavoprotein NifL in response to changes in oxygen or nitrogen levels. NifL contains a PAS domain, which is an ubiquitous motif present in all kingdoms of life. PAS domains are involved in many regulatory signal transduction processes in a large variety of organisms and they function as on-off switches.
In this research the structure and function of this domain has been studied extensively using NMR and X-ray spectroscopy. Comparison of 1000 PAS protein sequences with predicted three dimensional structures resulted in a redefinition of this intriguing sensory domain.
T-DNA tagging in Medicago truncatula
Scholte, M. - \ 2002
Wageningen University. Promotor(en): T. Bisseling. - S.l. : S.n. - ISBN 9789058087409 - 109
medicago truncatula - rhizobium - merken van genen - dna - knobbelvorming - stikstoffixatie - wortelknolletjes - medicago truncatula - rhizobium - gene tagging - dna - nodulation - nitrogen fixation - root nodules
Symbiotic interaction between rhizobia and leguminous plants leads to the formation of N 2 -fixing root nodules. This interaction shows a high degree of host specificity based on the exchange of chemical signals between the symbiotic partners. Although much is known about the bacterial genes required for the establishment of this interaction, less is known about the plant genes involved.
Symbiotic plant mutants serve as a tool to identify genes involved in nodulation and to study their function. However, the isolation of the affected gene(s) found in natural populations or induced by 'classical' methods like EMS treatment or irradiation is difficult, and so far only few of such genetically identified genes resulting in a mutant phenotype have been isolated. Problems to isolate a mutated gene can be overcome by the use of T-DNA as a mutagen, because the known nucleotide sequence of the T-DNA can serve as a starting point for the identification of the flanking sequences. T-DNA tagging not only facilitates the cloning of new genes, but at the same time provides insight in the function of the identified genes. In addition, when the T-DNA tag contains a promoter-less reporter gene transcriptional and translational gene fusions may provide new marker genes for the different stages of nodule development.
The aim of the thesis work was to assess the possibilities of T-DNA tagging as a tool to discover M. truncatula genes involved in symbiosis and to study their function.
For this, a T-DNA insertion mutagenized M. truncatula population was produced and screened for GUS staining patterns and mutant phenotypes. Nineteen out of 187 lines showed GUS staining in the roots or the nodules and one line showed, in addition to the GUS staining, a dwarf phenotype.
The isolation and characterization of the T-DNA flanking regions of a selection of the GUS expressing lines showed that in two lines the T-DNAs had inserted in the ORF of a Narf -like gene (causing the dwarf phenotype in homozygous knock-outs) and in the ORF of a MtN3 -like gene (probably causing letality), respectively.
T-DNA tagging thus can be used as a tool for the discovery of genes or the production of new markers in M.truncatula
Lachgasemissie uit door klaver gebonden stikstof : verslag van een praktijkproef in Doorn
Corré, W.J. ; Hattum, Th.G. van; Pinxterhuis, J.B. - \ 2002
Wageningen : Plant Research International - 18
weidevlinderbloemigen - broeikaseffect - stikstofoxiden - luchtverontreiniging - graslanden - trifolium repens - klavers - stikstoffixatie - distikstofmonoxide - emissie - pasture legumes - greenhouse effect - nitrogen oxides - air pollution - grasslands - trifolium repens - clovers - nitrogen fixation - nitrous oxide - emission
Stable nitrogen isotopes : study about its use in the assessment of denitrification and N fixation
Carratala Sanchez, C. - \ 2001
Wageningen : Plant Research International (Note / Plant Research International 145) - 19
stikstof - stikstofkringloop - stabiele isotopen - stikstoffixatie - denitrificatie - meting - methodologie - nitrogen - nitrogen cycle - stable isotopes - nitrogen fixation - denitrification - measurement - methodology
|Nitrogen fixation in tropical cropping systems
Giller, K.E. - \ 2001
Wallingford : CAB International - ISBN 9780851994178 - 423
stikstoffixatie - stikstofbindende bacteriën - stikstofbindende bomen - bodembiologie - knobbelvorming - wortelknolletjes - rhizobium - teeltsystemen - peulgewassen - stikstof - nitrogen fixation - nitrogen fixing bacteria - nitrogen fixing trees - soil biology - nodulation - root nodules - cropping systems - legumes - nitrogen