Thesis (M. Sc.) -- Lincoln University, 2009. / Also available via the World Wide Web.

The influence of hyperaccumulator and phytostabilizing plants on soil solution chemistry and subsequent metal dynamics in the rhizosphere was investigated to gain a better understanding of the mechanisms governing metal availability and plant uptake at the soil:root interface during phytoremediation of metal contaminated soils.

Phytophthora cinnamomi is an important pathogen of many plant species in natural ecosystems and horticulture industries around the world. In Western Australia, a high proportion of native plant species are susceptible to P. cinnamomi attack. Acacia pulchella, a resistant legume species native to Western Australia has been considered as a potential biological control tool against P. cinnamomi. To develop effective control methods, it is important to understand the interactions between the control agent and the different life forms of the pathogen. In this thesis the interactions are investigated between P. cinnamomi and varieties of A. pulchella which occur in jarrah (Eucalyptus marginata) forest and sand plain ecosystems. The soil inoculum of P. cinnamomi was compared under the potted plants of the three common varieties of A. pulchella, var. pulchella, var. glaberrima and var. goadbyi. These were grown in infected jarrah forest soil in the glasshouse and in vitro in a sterilised soil-less mix aseptically. Acacia urophylla (a species non suppressive towards P. cinnamomi) was also included as a control. An isolate of the most commonly found clonal lineage of P. cinnamomi in the jarrah forest, A2 type 1 was selected for use in experiments after testing showed it reliably produced zoospores and chlamydospores both axenically and in non-sterile conditions, in comparison to several other isolates. The lowest survival of P. cinnamomi inoculum was found under A. pulchella var. goadbyi plants grown both in non sterile soil and in aseptic soil-less mix. All the life forms of P. cinnamomi were affected by A. pulchella (Chapters 2, 3, 4 and 5). The soil leachates from potted plants of A. pulchella var. goadbyi reduced sporangial production (Chapter 2) and caused cytoplasm collapse of chlamydospores (Chapter 3). The confirmation was obtained that soil under A. pulchella was inhibitory to sporangial stage of P. cinnamomi and new evidence was obtained on chlamydospore inactivation. Cytoplasm collapse in the chlamydospores was observed both for chlamydospores on mycelial discs on Mira cloth exposed to the soil leachate and within infected roots buried in soils under the three varieties of A. pulchella plants. The effect was strongest under the plants of A. pulchella var. goadbyi and indicated that the chlamydospores of P. cinnamomi are unlikely to act as persistent structures under A. pulchella var. goadbyi plants. In Chapter 4, bioassays were conducted with axenically produced mycelia, chlamydospores and zoospores to test the inhibitory effect of the root exudates collected from aseptically grown A. pulchella var. goadbyi plants. The zoospores of the same isolate used in the soil leachate tests were immobilised (became sluggish and encysted) within one to two minutes. When incubated for 24 h, zoospores predominantly clumped and germ tubes were observed only from the clumped ones. Chlamydospores produced by four isolates of the common A2 type 1 strain and the only one A2 type 2 strain available at the time were tested. A higher percentage of chlamydospores collapsed and a very low percentage germinated after 24 h. Chlamydospores of all the A2 type 1 isolates were inhibited by the root exudates whilst the A2 type 2 isolate remained viable. The findings showed that the suppressive effect must be due at least in part to substances exuded by the A. pulchella plants. However, it appeared that the A2 type 1 isolates were more vulnerable to this effect than the single A2 type 2 isolate. In Chapter 5, the effect of season on sporangial suppression of P. cinnamomi was shown using field soils collected from three jarrah forest soil vegetation types and a Banksia woodland on Bassendean sand, collected in winter and summer. The effect of age of A. pulchella plants was demonstrated using the soils collected from rehabilitated bauxite mine pits. In all the locations soils were collected under A. pulchella plants and 5 m away from the nearest A. pulchella. An effect of soil type was evident as whilst the soil leachates made from the three lateritic jarrah forest soil types where A. pulchella is common in the understorey were suppressive to the sporangial stage of P. cinnamomi, this effect was not evident in the Bassendean sand under A. pulchella. A. pulchella soils collected in winter were less suppressive towards sporangial production than soils collected in summer. An effect of plant age was demonstrated as soil leachates from four year-old A. pulchella stands in rehabilitated bauxite mine sites were more suppressive for sporangia than leachates from one year-old stands. Further information on the behaviour of the pathogen in soil and in potting mix with and without A. pulchella was obtained by infecting lupin radicles with an isolate of each A2 type, 1 and 2 strains of P. cinnamomi and burying them in the soil under the three varieties of A. pulchella plants. After a week, the chlamydospores were mostly collapsed and hyphae deteriorated. Oospores were observed and in significant numbers under the potted plants of A. pulchella var. glaberrima. Isolates of all three clonal lineages of P. cinnamomi found in Australian soil were tested for the ability to produce oospores. Two isolates of the A1 and A2 type 2 and three isolates of the common A2 type 1 were screened. The two isozyme types of the A2 clonal lineage isolated in Australia varied in ability to self and produce oospores in planta in several soils from the jarrah forest. The isozyme type 2 of the A2 clonal lineage of P. cinnamomi produced oospores under these experimental conditions. This stimulation was not effective for most of the tested isolates of the A2 type 1 and the A1 clonal lineage. The in planta oospores were viable but dormant and the oogonial-antheridial associations were amphigynous both in vitro and in vivo. For the first time it was established that, the stimulus for selfing and oospore formation in the A2 type 2 of P. cinnamomi is available in some jarrah forest soils, with and without A. pulchella and also in the potting mix used. This raises important questions for the management of the pathogen. Several factors were identified as potential stimuli for selfing. Among them, soil nutrient levels and essentially enhanced sulphur presence were found important. Temperature also played a key role. Oospores were produced abundantly at 21 – 25 ºC but not over 28 ºC. The biology of P. cinnamomi has been studied for several decades but some important aspects remain un-researched. This thesis pioneers research into the in planta selfing aspect of the pathogen in soil. It also improved the understanding of the interactions between P. cinnamomi and A. pulchella which to some extent supports use of A. pulchella as a biological control tool against P. cinnamomi. However, attention is drawn to the natural mechanisms of this complex pathogen to survive in planta by producing oospores, the most persistent form of its life cycle.

Thesis (Ph. D.)--Oregon State University, . / Printout. Includes bibliographical references. Also available on the World Wide Web.

This study examined the rehabilitation potential of AM fungi with organic and inorganic fertilisers under pot and field trial conditions as well as their interaction with rhizospheric organisms and specific functional groups. In addition, the study highlighted the effects of land-use management on AM fungal populations in soil and the mycorrhizal status of some selected plants from one of the study sites. The study focussed on two sites that differ in operational activities and these included a mined area that was to be rehabilitated and a commercial farming site. A pot trial was conducted using an overburdened soil resulting from kaolin clay mining. Pots were seeded with Cynodon dactylon and treated with either Organic Tea or NPK (3:1:5) fertiliser, with or without AM fungal inoculum. The compatibility of these fertilisers with AM fungi was assessed by plant growth and percentage root colonisation. Maximum shoot height and plant biomass were observed at the 28th week with NPK (3:1:5) fertiliser supporting mycorrhizal colonisation by 80%. The result indicated the potential of AM fungi to be used in rehabilitation with minimal phosphate fertiliser. Similarly, a field trial was set-up using 17 x 17 m[superscript 2] plots in the mining site that were treated with the same organic and inorganic fertilisers as well as with AM fungal inoculum in different combinations. The interaction between AM fungi and soil microbial population was determined using culture dependent and culture independent techniques. The culture dependent technique involved the use of soil dilution and plating on general purpose and selective media. The result showed that there was no change in the total culturable bacterial number in the untreated and AM fungal treated plots, while a change in species composition was observed in the functional groups. Different functional groups identified included nitrogen fixing bacteria, pseudomonads, actinomycetes, phosphate solubilisers and the fungal counterparts. Gram-positive bacteria were observed as the predominant phenotypic type, while nitrogen fixers and actinomycetes were the predominant functional groups. Species identified from each functional group were Pseudomonas fulva, Bacillus megaterium, Streptomyces and actinomycetales bacteria. Meanwhile, fungi such as Ampelomyces, Fusarium, Penicillium, Aspergillus, Cephalosporium and Exserohilium were identified morphologically and molecularly. Furthermore, the mining site had a significantly higher bacterial number than the farming site thereby indicating the effects of land-use management on culturable bacterial numbers. The culture independent technique was carried out by cloning of the bacterial 16S rDNA and sequencing. Identified clones were Bradyrhizobium, Propionibacterium and Sporichthya. A cladogram constructed with the nucleotides sequences of identified functional species, clones and closely related nucleotide sequences from the Genbank indicated that nucleotide sequences differed in terms of the method used. The activity and establishment of the introduced AM fungal population was determined by spore enumeration, infectivity assay, percentage root colonisation and assessment of glomalin concentrations. The results indicated that the two land use types affected AM fungal populations. However, the establishment of AM fungi in the farming site was more successful than in the mining site as indicated by the higher infectivity pontential. Selected host plants, which were collected around the mine area, were observed to be mainly colonised by AM fungi and these were identified as Pentzia incana, Elytropappus rhinocerotis, Euphorbia meloformis, Selago corymbosa, Albuca canadensis and Helichrysum rosum. These plant species were able to thrive under harsh environmental conditions, thereby indicating their potential use as rehabilitation host plants. Generally, the findings of this study has provided an insight into the interaction between arbuscular mycorrhizal fungi and other soil microorganisms in two fields with differing land use management practices.

Cette étude s’inscrit dans le contexte du stockage profond de déchets radioactifs sur le site de Meuse-Haute Marne (Andra) et plus précisément de l’évolution bio-physico-chimique de roches sédimentaires argileuses (Callovo-Oxfordien, COx), excavées et stockées en surface sous forme de verses. Durant la phase préparatoire et la phase d’exploitation, plusieurs millions de mètres cubes d’argilites seront excavées. L’argilite stockée à l’air libre sera ainsi exposée durant plusieurs décennies aux altérations météoritiques et aux conditions oxydantes de surface et à la colonisation biologique (plantes, bactéries, champignons). L’objectif de la thèse était d’étudier l’impact de molécules antioxydantes et de la végétalisation des verses par des plantes produisant ces molécules, sur les processus d’altération physiques, chimiques ou microbiens de l’argilite du COx. Ce travail visait à (i) identifier des molécules antioxydantes et des plantes d’intérêt (ii) évaluer les effets inhibiteurs des substances antioxydantes sur l’altération des minéraux et la lixiviation des métaux du COx au laboratoire, (iv) tester la cultivabilité des plantes sélectionnées sur les verses, (iii) suivre in situ l’évolution physico-chimique et microbiologique de l’argilite d’une verse plantée ou non. Des expériences de percolation en colonnes avec des molécules antioxydantes « modèles » des Lamiacées (linalol, thymol, carvacrol) ont montré des taux d’altération/lixiviation très variables en fonction de l’élément. Ils étaient très faibles pour l’aluminium (<1‰), compris entre 1-3% pour les autres métaux (Ca, Mg, Fe…) et atteignaient plus de 60% pour le sodium. Avec le thymol à 20 mg/l ont été observés sur 3 mois une diminution des taux de lixiviation du soufre et des éléments métalliques constitutifs des sulfures (Fe, As) et carbonates (Ca, Sr) et une diminution de l’abondance microbienne bactérienne et fongique. Cependant, l’apport d’exsudats racinaires synthétiques dans les colonnes a stimulé le développement microbien et amélioré la disponibilité de l’aluminium et du fer et la séquestration du calcium. Parmi les plantes testées, la lavande et le lavandin ont été sélectionnés. Deux essais successifs de plantations ont été menés in situ sur une verse d’argilite âgée (10 ans) durant un an. Le lavandin s’est mieux développé que la lavande et a été conservé pour la deuxième étude in situ. La comparaison de la partie plantée de la verse avec la partie nue a montré (i) une diminution significative des quantités de calcium, strontium, fer et soufre lixiviées (ii) une réduction importante de la quantité de matériel érodé (de deux ordres de grandeur) sur le talus planté par rapport au non planté (iii) un développement microbien et un taux de mycorhization important des racines. En conclusion, même si les molécules antioxydantes n’inhibent pas significativement l’altération de l’argilite, le lavandin s’est révélé une plante tout à fait pertinente pour la phytostabilisation des verses et la production de molécules antioxydantes in situ a été montrée / This study is a part of the deep disposal site development for radioactive waste in Meuse-Haute Marne (France), most specifically on the bio-physico-chemical conversion of sedimentary clay rocks (Callovo-Oxfordian, COx), excavated and stored on surface in the form of heap. During the experimental and operational phases, several million cubic meters of argillite will be excavated. Argillite stored in the open air will be exposed to meteoritic alterations, oxidizing conditions of surface and colonized biologically (plants, bacteria, fungi). The aim of the thesis is to study the impact of naturally derived antioxidants from revegetation of heap with antioxidant-producing plants on the physical, chemical or microbial weathering processes of argillite. This work was designed to (i) identify suitable naturally derived antioxidants and the plants to produce them (ii) assess the antioxidant inhibitory effects on weathering and leaching COx metals in the laboratory, (iv) field test selected plants on the heap, (iii) follow in situ physicochemical and microbiological evolution of the argillite heap planted with antioxidant producing plants. In the laboratory, percolating model antioxidants of Lamiaceae (linalool, thymol, carvacrol) through a packed column of argillite showed variable water weathering/leaching rate depending on the metal elements present; very low for aluminum (<1 ‰), between 1-3% for other metals (Ca, Mg, Fe ...) and reach more than 60% for sodium. With thymol at 20 mg/l for 3 months, it was found that there are a decrease in sulfur leached amount and the metal elements from the sulfides (Fe, As) and carbonates (Ca, Sr) and inhibition of bacterial and fungal microflora growths. However, intake of artificial root exudates in columns stimulates microbial growth, improves the availability of aluminum, iron and provides sequestration of calcium. Among the tested plants, lavender and lavandin were selected. Two successive plantation tests were carried out in situ on a heap of old argillite (10 years) for one year. The lavandin grew better than lavender and was retained for the second study in situ. The comparison of the planted part of the COx heap with bare COx showed (i) a significant reduction in the quantities of calcium, strontium, iron and sulfur leached (ii) a significant reduction (by two orders of magnitude) to the amount of eroded material on the slope planted compared to unplanted (iii) a significant rate of mycorrhiza roots and microbial growth. In conclusion, although the naturally derived antioxidants did not significantly inhibit the alteration of argillite, the lavandin is an excellent plant for phytostabilisation of heap and for production of antioxidants.

Submitted by ROBERTH NASCIMENTO DA TRINDADE null (octuberman@gmail.com) on 2016-02-02T12:22:18Z No. of bitstreams: 1 ROBERTH TRINDADE - Exploração racional da rizosfera de Senna spectabilis - interações entre as bactérias Pseudoxanthomonas indica e Shigella sp..pdf: 2399531 bytes, checksum: 1d992c19e1d2db2f229774b0f45cc074 (MD5) / Approved for entry into archive by Sandra Manzano de Almeida (smanzano@marilia.unesp.br) on 2016-02-03T17:44:59Z (GMT) No. of bitstreams: 1 trindade_rn_me_araiq_par.pdf: 740045 bytes, checksum: 46f1e680a7415dd924948bb180d6dfc7 (MD5) / Made available in DSpace on 2016-02-03T17:44:59Z (GMT). No. of bitstreams: 1 trindade_rn_me_araiq_par.pdf: 740045 bytes, checksum: 46f1e680a7415dd924948bb180d6dfc7 (MD5) Previous issue date: 2016-01-22 / O descobrimento de novas moléculas bioativas tem sido o grande alvo ao decorrer dos anos da química dos produtos naturais, particularmente, micro-organismos tem se evidenciado como uma importante fonte do descobrimento de novos fármacos. Uma ampla gama de compostos provenientes de organismos microbianos são relatados na literatura, porém, recentes pesquisas demonstram que tais micro-organismos podem sofrer indução por determinados agentes externos, químicos ou físicos, através de mecanismos de defesa ou até mesmo o mutualismo existente em determinado meio, produzindo novas estruturas químicas, que até então, tinham sua rota biosintética silenciada devido a metodologias padrões de cultivo isolado. Através de utilização de culturas mistas de bactérias, o presente trabalho proporciona o conhecimento da relação existente entre Pseudoxanthomonas indica e Shigella sp., ambas provenientes da rizosfera de Senna spectabilis. Para isso, as bactérias foram cultivadas em meio de cultivo líquido czapek broth, sendo realizado o estudo do crescimento das bactérias e produção de metabolitos frente ao tempo, tendo em vista uma maximização de resultados e maior indução de compostos químicos. A utilização de ferramentas analíticas de análise rápida e eficiente como a cromatografia líquida de alta eficiência (HPLC) associada à espectrometria de massas de alta resolução (HRMS) propiciaram a obtenção do perfil cromatográfico dos micro-organismos estudados em cultura mista e simples, sendo possível observar a existência de compostos químicos produzidos apenas em co-cultura, evidenciado o potencial existente da abordagem utilizada. / The discovery of new bioactive molecules has been the big target to over the years the chemistry of natural products, particularly micro-organisms has been shown to be an important source of discovery of new drugs. A wide range of compounds from microbial organisms are reported in the literature, however, recent research shows that these micro-organisms can undergo induction by certain external, chemical or physical agents, through defense mechanisms or even the existing mutualism on a particular medium, producing new chemical structures, which until then had silenced their biosynthetic route due to methodologies patterns of isolated farming. Through use of mixed cultures of bacteria, this study provides knowledge of the relationship between Pseudoxanthomonas indica and Shigella sp., Both from the rhizosphere of Senna spectabilis. For this, bacteria were grown in liquid Czapek broth cultivation being conducted the study of the growth of bacteria and production of metabolites against time, with a view to maximizing results and greater induction of chemical compounds. The use of analytics quickly and efficiently analyzes such as high-performance liquid chromatography tools (HPLC) associated with high resolution mass spectrometry (HRMS) enabled the obtaining of the chromatographic profile of microorganisms studied in mixed and single culture, and you can to observe the existence of chemical compounds produced only in co-culture demonstrated the potential of the approach used.

Trichoderma spp. is at the present time, one of the fungi most studied as biocontrol agent, being antagonistic to several pathogens in different crops, besides promoting vegetable growth. The pathogen Fusarium oxysporum causes the fusarial wilt and is difficult to control mainly because of its capacity to remain in the soil for long periods, even without the presence of the host. Studies of the population dynamics of Trichoderma spp., Fusarium spp. and native microorganisms are necessary, mainly to observe the impact of the biocontrol agent addition to the soil. Vegetables as cucumber and tomato are commonly cultivated in South Brazil and are sensitive to a variety of diseases, as the fusarial wilt which is one of, their main diseases, specially in protected environment. For the biological control of the fusarial wilt in the cultivation of tomato and cucumber by Trichoderma and to study the population dynamics of the biocontrol agent when added to the soil, the following objectives were proposed: to study the space distribution of both Trichoderma and Fusarium in rhizosphere and bulk soil, in the cultivation of cucumber and tomato, in vegetable garden and greenhouse; to find a method for the mass selection of fungi isolates antagonistic to Fusarium solani and Fusarium oxysporum in microenvironment, and to identify the more effective ones; to verify the action of Trichoderma harzianum isolates in the development and protection of seedlings against the fusarial wilt of tomato and cucumer, identifying the best form of the biocontrol agent application in the control of the fusarial wilt; to analyze the population dynamics of Trichoderma and Fusarium, and of part of the microorganisms of the soil, with the addition of the biocontrol agents, in the cultivation of the tomato and cucumber, in greenhouse and vegetable garden. Both Trichoderma and Fusarium were found in the rhizosphere and bulk soil and the rhizosphere soil had the greater frequence of Trichoderma specially in greenhouse. The method of mass selection, in substrat, of fungi isolates antagonistic to the pathogens F. solani and F. oxysporum was efficient, since the three isolates of Trichoderma harzianum selected, besides reducing the population of the pathogens in substrate were also effective against the fusarial wilt of tomato and cucumber when applied as seed or substrate treatment. A population flutuation of Trichoderma spp. ocurred when isolates of T. harzianum were added to the soil in the cultivation of tomato and cucumber, in vegetable garden and greenhouse. There was a tendency of the population of Trichoderma spp. to return to the initial parameters, i.e. before the biocontrole agent was added to the soil. The population of bacteria, Fusarium spp. and general fungi did not show great alterations with the presence of the isolates of the biocontrol agent. / Trichoderma spp. é um dos fungos mais pesquisados na atualidade como agente de biocontrole, sendo antagonista a vários fitopatógenos em diferentes culturas, além de auxiliar no desenvolvimento vegetal. O patógeno Fusarium oxysporum causador da murcha de fusário ou fusariose é difícil de ser controlado, principalmente pela sua capacidade em manter-se no solo por longos períodos, mesmo sem a presença do hospedeiro. Estudos da dinâmica populacional de Trichoderma spp., Fusarium spp. e microbiota nativa são necessários, principalmente para observar-se o impacto da adição do agente de biocontrole no ambiente solo. Olerícolas, como pepineiro e tomateiro, são comumente cultivadas na Região Sul, porém são sensíveis a uma gama de doenças, dentre as quais, a fusariose, que figura como principal doença, principalmente em ambiente protegido. Para buscar o controle biológico da fusariose no cultivo do tomateiro e pepineiro por Trichoderma e estudar a dinâmica populacional desse agente de biocontrole quando adicionado ao solo, foram propostos os seguintes objetivos: estudar a distribuição espacial dos gêneros Trichoderma e Fusarium em solo rizosférico e não rizosférico, no cultivo do pepineiro e tomateiro, em horta e estufa; utilizar micro-ambiente para realizar a seleção massal de isolados fúngicos antagônicos a Fusarium solani e Fusarium oxysporum e identificar, em nível de espécie, os isolados fúngicos mais efetivos; verificar a ação de isolados de Trichoderma harzianum no desenvolvimento e na proteção de mudas contra a murcha de fusário do tomateiro e do pepineiro, identificando a melhor forma de aplicação do agente de biocontrole no controle da fusariose; analisar a dinâmica populacional dos gêneros Trichoderma e Fusarium e de parte da microbiota do solo, com a adição de agente de biocontrole, no cultivo do tomateiro e pepineiro, em estufa e horta. Tanto Trichoderma quanto Fusarium foram encontrados em solo rizosférico e não rizosférico de horta e estufa, sendo que Trichoderma foi encontrado em maior número de coletas em solo rizosférico de estufa. O método de seleção massal, em substrato, de isolados fúngicos antagônicos aos patógenos F. solani e F. oxysporum foi eficiente, pois os três isolados de Trichoderma harzianum selecionados, além de reduzirem a população dos patógenos em substrato, foram efetivos contra a fusariose do tomateiro e pepineiro, em tratamento de semente ou de substrato. Ocorreu flutuação populacional de Trichoderma spp. quando isolados de T. harzianum foram adicionados ao solo no cultivo do tomateiro e pepineiro, em horta e estufa. Observou-se uma tendência da população de Trichoderma spp. voltar aos parâmetros iniciais, ou seja, antes do agente de biocontrole ser adicionado ao ambiente solo. A população de bactérias, Fusarium spp. e fungos gerais não apresentou grandes alterações pela presença dos isolados do agente de biocontrole.

Submitted by ELIALDO ALVES DE SOUZA (eli_agronomo@yahoo.com.br) on 2017-07-03T17:28:37Z No. of bitstreams: 1 SOUZA, E.A..pdf: 3660134 bytes, checksum: bce1034cb117c1be8df868aa0e61ab8f (MD5) / Approved for entry into archive by Luiz Galeffi (luizgaleffi@gmail.com) on 2017-07-04T18:06:29Z (GMT) No. of bitstreams: 1 souza_ea_dr_bot.pdf: 3660134 bytes, checksum: bce1034cb117c1be8df868aa0e61ab8f (MD5) / Made available in DSpace on 2017-07-04T18:06:29Z (GMT). No. of bitstreams: 1 souza_ea_dr_bot.pdf: 3660134 bytes, checksum: bce1034cb117c1be8df868aa0e61ab8f (MD5) Previous issue date: 2017-02-13 / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / A aplicação de amônio pode, em algumas condições, melhorar a eficiência de uso do fósforo (EUP) e o desenvolvimento do milho, especialmente em solos tropicais, normalmente ácidos e pobres em P disponível. O presente trabalho tem por objetivo estudar o efeito da adubação amoniacal sobre o aproveitamento do P, as condições bioquímicas da rizosfera, a morfologia radicular e o desenvolvimento da cultura do milho. Os dois experimentos iniciais foram conduzidos em casa de vegetação, o primeiro em vasos de 12 L e o segundo em Plant Growth Containers (PGCs), com solo previamente corrigido e adubado segundo os tratamentos: 3 (três formas de adubação nitrogenada - amoniacal, nítrica e mista) x cinco doses de fosfato (0, 40, 80, 120 e 160 mg P kg-1 de solo). Aos 35 dias após a emergência as raízes foram removidas dos containers e vasos e as amostras de planta e solo foram coletadas para análises. O solo rizosférico no experimento I foi obtido por “agitação-lavagem” e no experimento II por “fatiamento em camadas”, de forma que quatro das oito repetições foram congeladas frescas (análises: amônio, nitrato, C orgânico e P microbiano) e quatro foram transformadas em TFSE (análises: fracionamento químico do P e pH). As amostras de planta foram submetidas a pesagem e análise nutricional. O experimento III foi conduzido em um sistema de scanners em solução nutritiva de acordo com os tratamentos: 2 (amônio ou nitrato) x (alta dose ou baixa dose de P), com 10 repetições. Imagens foram obtidas diariamente para avaliação do desenvolvimento radicular. Ao final dos ensaios foram obtidos peso fresco e seco, análises de P em tecidos e, com dados de diferentes parâmetros radiculares, foi feito o desenho da planta média no RootBox. Os tratamentos com amônio e nitrato + amônio, na dose mais alta de P no experimento I ou em todas as doses no experimento II, resultaram em maior produção de matéria seca, menor relação raiz: parte aérea, desenvolvimento de raiz mais aequado à absorção de P, maior recuperação de P, maior acúmulo de amônio, nitrato e N-mineral nas camadas mais próximas ao rizoplano, menor pH, maior mobilização de formas menos lábeis de P, maior consumo de P geoquímico e P biológico. Houve diferença entre solo rizosférico e solo não rizosférico e entre as diferentes camadas da rizosfera, para todos os parâmetros, entre as formas de nitrogênio. O amônio e nitrato + amônio resultaram em maior produção de C orgânico solúvel em água e maior dose de superfosfato triplo resultou em maior quantidade de P na fração microbiana. O amônio resultou desenvolvimento radicular mais ramificado e com maior número de raízes laterais. O amônio melhora a eficiência de uso do P, devido às mudanças químicas e biológicas na rizosfera, e às mudanças na arquitetura radicular, que favorecem a solubilidade, a mineralização e a absorção de fosfato e, consequentemente, aumenta a produção de matéria seca nos estádios iniciais da cultura do milho. / Ammonium application can improve phosphorus use efficiency (PUE) and the development of maize plants, especially in tropical soils, usually acids and P-limiting. The aim of this study is evaluate how ammoniacal fertilization impacts the P use efficiency (PUE), the biochemical conditions of the rhizosphere, the root morphology and the development of maize plants. Two initial experiments were carried on greenhouse, the first one in pots of 20 L and the second one in Plant Growth Containers (PGCs), using soil after liming and fertilized according to the following treatments: 3 (nitrogen fertilization: ammonium only, nitrate only and both) x five doses of phosphate (0, 40, 80, 120 and 160 mg P kg-1 of soil). At 35 days after emergence the roots were removed from the containers and pots and the plant and soil samples were collected for analysis. The rhizosphere soil in experiment I was obtained by "shaking-washing" and in the experiment II by "layer slicing". Four of the eight soil replicates were fresh frozen (analyzes: ammonium, nitrate, organic C and microbial P) and four of them were dried (analyzes: chemical fractionation of P and pH). Plant samples were weighed and analyzed for P content. The experiment III was carried on a system of nutrient solution scanners according to the treatments: 2 (ammonium or nitrate) x (high or low dose of P), with 10 replicates. Images were obtained in daily basis for the evaluation of root development. At the end of the tests, fresh and dry weights and P content were obtained. Data of different root traits were used to draw the average plant on the RootBox. The treatments with ammonium and nitrate + ammonium, plus the highest dose of P in the experiment I or at all doses in the experiment II, resulted in higher dry matter yield, lower root ratio: aerial part, root development adequate for P absorption, higher P recovering, higher ammonium, nitrate and N-mineral accumulation in the nearest layersto the rhizoplane, lower pH, greater mobilization of less labile P forms, higher mobilization of geochemical and biological P. There were differences between rhizospheric and bulk soils and between the different layers of the rhizosphere, for all parameters and treatments. Ammonium and nitrate + ammonium resulted in higher organic C water soluble organic C, and higher dose of triple superphosphate resulted in higher amount of P in the microbial fraction. Ammonium resulted in a branched root with a greater number of lateral roots. Ammonium improves the use efficiency, solubility, mineralization and uptake of P, due to chemical and biological changes in the rhizosphere and root architecture in the early stages of corn development. / FAPESP: 13/18870-1 / FAPESP: 15/12399-0

Em solos tratados com lodo de esgoto, a concentração de metais pesados em solução é baixa e a cinética de dissolução é lenta. Com isso, as reações de complexação que ocorrem na rizosfera passam a ser importantes para a fitodisponibilidade destes metais. Estudos recentes demonstraram que ácidos orgânicos liberados por raízes, como acético, cítrico, láctico, oxálico e tartárico, são importantes agentes complexantes e, conseqüentemente, fitodisponibilizadores de metais pesados. Soluções de ácidos acético, cítrico, lático, oxálico e tartárico, nas concentrações: 0,4; 0,6; 0,8 e 1,00 mol L-1 foram utilizadas para extrair Cd, Cu, Cr, Ni, Zn e Pb de amostras de um LATOSSOLO VERMELHO AMARELO Distrófico (LVAd) e de um LATOSSOLO VERMELHO Eutroférrico (LVef) tratados com doses de 0, 40 e 80 Mg ha-1 de lodo de esgoto. Nas mesmas amostras foram cultivadas plantas de arroz, pelo método de Neubauer. Os teores de metais pesados nas plantas, colhidas 18 dias após a germinação, foram correlacionados com os teores extraídos pelas diferentes soluções dos ácidos orgânicos. Os resultados mostraram que a fitodisponibilidade de Cu e Zn pode ser estimada por todos os ácidos estudados e em todas as concentrações. Os ácidos lático e tartárico, em concentrações de 0,4 até 1 mol L-1, apresentaram potencial para estimar a disponibilidade Ni, e o ácido oxálico, em todas as concentrações, para Cr. Com aplicação de doses de lodo de esgoto de até 80 Mg ha-1 (base seca) não é prevista a disponibilidade de Cd e Pb, por isso não foi possível avaliar a eficiência dos ácidos orgânicos na previsão da fitodisponibilidade desses elementos. / In soils treated with sewage sludge, heavy metals concentration in solution is low and solubilization kinetics is slow. So, soluble complex formation that occurs in the rhizosphere became to be important in plant availability of these metals. Recent studies showed that organic acids released by roots, like acetic, citric, lactic, oxalic and tartaric acids, are important agents of solubilization and consequently can change heavy metals availability. Solution of acetic, citric, lactic, oxalic and tartaric acids in concentrations: 0.4, 0.6, 0.8, and 1.0 mol L-1 were used to extract Cd, Cu, Cr, Ni, Pb and Zn of soil samples treated with sewage sludge, in levels of 0, 40 and 80 Mg ha-1. Soils samples were also used in a Neubauer essay with rice as test plant. Heavy metals concentrations in the plants harvested 18 days after the germination were correlated with metals quantities removed from the different organic acid solutions. The results showed that Cu and Zn plant availability can be evaluated with all tested acids in all tested concentrations. Lactic and tartaric acids, 0.4 to 1.0 mol L-1, can be used to evaluate availability of Ni and oxalic acid, in all concentrations, can be a Cr extractant. . In the treatment receiving 80 Mg ha-1 of sewage sludge the Cd and Pb were not available as a result it was not possible to determine the organic acids efficiency to evaluate the bioavailability of these elements.