Le nitrate, source majeur d’azote pour la plupart des plantes,n’est pas seulement un élément nutritif mais est aussi une molécule signale. Il existe cependant des réponses au nitrate contrastées entre les différentes plantes supérieures. Chez Medicago truncatula, espèce modèle de la famille des légumineuses, le nitrate a un effet inhibiteur sur la croissance de la racine primaire en phase post-germinative. Une étude de génétique quantitative a montré qu’un transporteur de nitrate se situe au pic d’un QTL impliqué dans la croissance de la racine primaire. La caractérisation fonctionnelle de ce transporteur, nommé MtNRT1.3 et renommé MtNPF6.8, a montré que celui-ci est à double affinité pour le nitrate. Ce transporteur est alors susceptible de participer à l’influx de nitrate dans la plante. Après l’obtention de trois génotypes mutants RNAi stables, les expérimentations utilisant duK15NO3 ont montré que ce transporteur participe effectivement à l’influx de nitrate lié au système de transport à faible affinité inductible dans la plante (iLATS). En revanche,la mutation de MtNPF6.8 ne semble pas avoir de conséquence sur le métabolisme azoté. Par ailleurs, les études sur la croissance de la racine primaire ont permis de confirmer l’implication du transporteur sur ce caractère phénotypique. L’inhibition de croissance de la racine primaire observée sur nitrate chez le génotype sauvage est alors imputée, à l’échelle cellulaire, à une modulation de l'élongation cellulaire. La possibilité que l’ABA, hormone végétale, joue un rôle dans la médiation de cette réponse dépendant du nitrate, est fortement favorisée. L’ensemble de résultats, conforté par une étude de mutants exprimant ce transporteur chez A. thaliana, indique donc que MtNPF6.8 est un senseur de nitrate pour la plante en phase post germinative,ceci indépendamment de sa fonction de transport de nitrate. / Nitrate, a major nitrogen source for most plants, is not only anutrient but also a signaling molecule. However, there arecontrasting responses to nitrate between different higherplants. In the model legume Medicago truncatula, nitrate hasan inhibitory effect on the primary root growth in postgerminationphase. A quantitative genetic study has shownthat a nitrate transporter is localized at the peak of a QTLinvolved in the primary root growth. Functionalcharacterization of the transporter, named MtNRT1.3 andrenamed MtNPF6.8, showed that it encodes a dual affinitynitrate transporter. MtNPF6.8 is likely to participate in thenitrate influx in the plant. After obtaining three knockdownlines by RNA interference, experiments using K15NO3 showedthat this transporter is effect involved in nitrate influx relatedto the inducible low affinity transport system (iLATS).However, mutation in MtNPF6.8 does not any effect onnitrogen metabolism. In addition, studies on the primary rootgrowth have confirmed the involvement of the transporteron phenotypic trait. In wild-type plants, cortical cell sizedecreased after nitrate treatment, showing that primary rootgrowth was due to this reduced cell elongation. Thepossibility that ABA also plays a role in mediating this nitratedependent response is heavily favored. All these results,reinforced by a study of mutants expressing this transporterin A. thaliana, indicate that MtNPF6.8 is a nitrate sensor forMedicago in the post-germination phase, independently ofits nitrate transport activity.

Made available in DSpace on 2014-08-20T13:25:42Z (GMT). No. of bitstreams: 1 Tese_Lorena_ Donini.pdf: 3190241 bytes, checksum: f4606822576585e47016056d80f7fb55 (MD5) Previous issue date: 2009-04-08 / The olive (Olea europaea L.) belongs to the Oleacea falmily, which include until 30 genera and 600 species distributed in tropical and temperate regions. The cutting is a widely used method, however the in vitro culture by micropropagation is a viable method of propagation providing the uniformity to the orchards, besides to enable the production of plants with health and accelerate the methods of conventional propagation. Thus, this work aimed to evaluate in vitro establishment and multiplication of olive through different treatments of culture medium. The article 1 aimed the in vitro established of different olive cultivars under different types of light and to evaluate combinations of zeatin and gibberellic acid of the in vitro establishment. The article 2 aimed to determine both the suitable culture medium and zeatin concentration for in vitro establishment of olive tree cv. Arbequina. The objective of article 3 was find alternatives to replace the use of zeatin or decrease this concentration in the culture medium to evaluate different cytokinins and concentrations of in vitro establishment and multiplication of olive tree cv. Arbequina. The article 4 aimed to evaluate two sugar types and concentrations on in vitro multiplication of olive cultivar Arbequina. The article 5 evaluated different types of closing and silver nitrate of in vitro multiplication of olive tree cultivar Arbequina. It was verified that: (1) the cultivars Koroneiki e Picual presented higher rate of in vitro establishment when cultivated under white light; the zeatin and AG3 combination is not efficient for in vitro establishment of olive tree; (2) the WPM and MO medium culture provide better results on in vitro establishment of olive cultivar Arbequina; (3) the use of 2 mg L-1 BAP is efficient for establishment and the use of 2 mg L-1 zeatin is efficient on in vitro multiplication of cultivar Arbequina; (4) Sucrose provides better results and the use of 15 g L-1 of sucrose is efficient as sugar source on in vitro multiplication of cultivar Arbequina; (5) the use of aluminum as sealing and the addition of 10 mg L-1 silver nitrate in the MO culture medium presents better results on in vitro multiplication of olive tree cultivar Arbequina. / A oliveira (Olea europaea L.) pertence à família Oleaceae, esta família inclui até 30 gêneros e 600 espécies distribuídas por regiões tropicais e temperadas. A estaquia é um método de propagação muito utilizado, mas o cultivo in vitro, por meio da micropropagação, é um método viável de propagação podendo assegurar a uniformidade dos pomares, além de possibilitar a produção de mudas com alta sanidade e acelerar os métodos de propagação convencional. Assim, este trabalho teve como objetivo estabelecer e multiplicar in vitro cultivares de oliveira através de diferentes tratamentos. O Artigo 1 consistiu no estabelecimento in vitro de diferentes cultivares de oliveira sob diferentes tipos de luz e avaliação de diferentes combinações de zeatina e ácido giberélico no estabelecimento in vitro. No Artigo 2 o objetivo foi determinar o meio de cultura e concentração de zeatina adequada no estabelecimento in vitro de oliveira cv. Arbequina. O Artigo 3 teve como objetivo buscar alternativas para substituir a utilização da zeatina ou diminuir a concentração desta no meio de cultura avaliando diferentes citocininas e concentrações no estabelecimento e multiplicação in vitro de oliveira cultivar Arbequina. O Artigo 4 teve como objetivo avaliar dois tipos de açúcar e concentrações na multiplicação in vitro de oliveira cultivar Arbequina. O Artigo 5 teve como objetivo avaliar diferentes tipos de vedação e nitrato de prata na multiplicação in vitro de oliveira cultivar Arbequina. De acordo com os resultados obtidos, na ordem dos artigos, verificou-se que: (1) as cultivares Koroneiki e Picual apresentam maior taxa de estabelecimento in vitro quando cultivadas sob luz branca; a combinação de zeatina e AG3 não é eficaz para o estabelecimento in vitro de oliveira; (2) os meios de cultura WPM e MO proporcionam melhores resultados no estabelecimento de oliveira Arbequina; (3) a utilização de 2 mg L-1 de BAP é eficiente para o estabelecimento e a utilização de 2 mg L-1 de zeatina é eficiente para a multiplicação in vitro de oliveira cultivar Arbequina; (4) dentre os açúcares testados, a sacarose proporciona melhores resultados e a utilização de 15 g L-1 de sacarose é eficiente como fonte de açúcar na multiplicação in vitro de oliveira cultivar Arbequina; (5) A utilização de papel alumínio como vedação e a adição de 10 mg L-1 de nitrato de prata ao meio de cultura MO apresenta melhores resultados na multiplicação in vitro de oliveira cultivar Arbequina.

Ingestion of vegetables rich in inorganic nitrate (NO3-) content has emerged as an effective method, via the formation of a nitrite (NO2-) intermediate, for acutely elevating vascular nitric oxide (NO) levels. As such a number of beneficial effects of NO3- ingestion have been demonstrated including the suggestion that platelet reactivity is reduced. I initially investigated whether inorganic NO3- supplementation might also reduce platelet reactivity in healthy volunteers and have determined the mechanisms involved in the effects seen. I conducted a randomised crossover study in 24 (12 of each sex) healthy subjects assessing the acute effects of potassium nitrate capsules (KNO3, 8 mmol) vs placebo (KCl) control capsule ingestion on platelet reactivity. Inorganic NO3- ingested via supplementation raised circulating NO3- and NO2- levels in both sexes and attenuated ex vivo platelet aggregation responses to adenosine diphosphate (ADP) and, albeit to a lesser extent, collagen but not epinephrine in male but not female volunteers. These inhibitory effects were associated with a reduced platelet P-selectin expression and elevated platelet cyclic guanosine monophosphate (cGMP) levels. In addition, I have shown that NO2- reduction to NO occurs at the level of the erythrocyte and not the platelet. These results demonstrate that inorganic NO3- ingestion, whether via the diet or through supplementation, results in a modest decrease in platelet reactivity in healthy males. I then sought to examine the effects of 6 weeks daily intake of NO3--rich beetroot juice versus a placebo NO3--deplete juice on endothelial and platelet function in a cohort of otherwise healthy non-diabetic untreated hypercholesterolaemics. In this randomised double blind placebo controlled parallel study 69 subjects were recruited. The primary end point was change in endothelial function determined using ultrasound flow-mediated dilatation (FMD). Secondary endpoints included change in pulse wave analysis (PWA), aortic pulse wave velocity (aPWV), platelet P-selectin and platelet monocyte aggregate (PMA) expression and plasma, urine and salivary NO3- and NO2- levels. Baseline characteristics, including lipid levels, were similar between the groups. Dietary NO3- caused an improvement in FMD of ~24% from 4.6%±2.2% to 5.7%±2.6% in the treatment group (p<0.001) not seen in the placebo group (4.5%±1.9% versus 4.3%±1.8% p=0.07). This improvement in FMD was also noted following acute administration of dietary NO3-. Small but significant improvements also occurred in aPWV and PWA augmentation index (p=0.04). The % of platelet monocyte aggregates was significantly reduced in the NO3- limb by 7.6% versus an increase of 10.1% in the placebo group (p=0.004). No adverse effects of dietary NO3- were detected. In this study population, chronic dietary NO3- ingestion improves endothelial function, vascular stiffness and platelet markers of atherogenesis in a cohort of hypercholesterolaemics who are otherwise at increased risk of cardiovascular disease (CVD). This thesis provides strong support for assessment of the potential of dietary NO3- as a primary prevention strategy to prevent atherothrombotic and atherogenic complications in larger cohorts.

Soil salinity is one of the major abiotic stresses that decreases agricultural crop production through imposition of both ionic and osmotic stresses. The accumulation of Na⁺ and Cl⁻ in the cytosol to toxic levels inhibits metabolism. Unlike Na⁺, less is known about Cl⁻ uptake and transport in plants. Grapevine is moderately sensitive to salinity and accumulation of toxic levels of Cl⁻ in leaves is the major reason for salt-induced symptoms. In this study Cl⁻ uptake and transport mechanism(s) were investigated in two grapevine (Vitis sp.) rootstock hybrids differing in salt tolerance: 1103 Paulsen (salt tolerant) and K 51-40 (salt sensitive). Increased external salinity caused high Cl⁻ accumulation in shoots of the salt sensitive K 51-40 in comparison to Paulsen. Measurement of ¹ ⁵ NO₃⁻ net fluxes under high salinity showed that by increasing external Cl⁻ concentrations K 51-40 roots showed reduced NO₃⁻ accumulation. This was associated with increased accumulation of Cl⁻. In comparison to Paulsen, K 51-40 showed reduced NO₃⁻ / Cl⁻ root selectivity with increased salinity, but Paulsen had lower selectivity over the whole salinity range (0-45 mM). In order to examine if root hydraulic and permeability characterisations accounted for differences between varieties, the root pressure probe was used on excised roots. This showed that the osmotic Lpr was significantly smaller than hydrostatic Lpr, but no obvious difference was observed between the rootstocks. The reflection coefficient (σ) values (0.48-0.59) were the same for both rootstocks, and root anatomical studies showed no obvious difference in apoplastic barriers of the main and lateral roots. Comparing the uptake of Cl⁻ with an apoplastic tracer, PTS (3-hydroxy-5, 8, 10-pyrentrisulphonic acid), showed that there was no correlation between Cl⁻ and PTS transport. These results indicated that by-pass flow of salts to the xylem is the same for both rootstocks (10.01±3.03 % and 12.1±1.21 %) and hence pointed to differences in membrane transport to explain difference in Cl⁻ transport to the shoot. ³ ⁶Cl⁻ fluxes across plasma membrane and tonoplast of K 51-40 and Paulsen roots showed that ³ ⁶Cl⁻ influx in root segments of Paulsen was greater than K 51-40 over the first 10 minutes. Unidirectional influx within 10 min loading time showed increases with increases in the external concentrations in both rootstocks but Paulsen had higher influx rate when compared to K 51-40. This appeared to be due to a greater Vmax. There was no significant difference in Km. It was shown that ³ ⁶Cl⁻ accumulation and transport rate to the shoot of K 51-40 was higher than that of Paulsen. Compartmental analysis of ³ ⁶Cl⁻ efflux from intact roots confirmed that the difference in influx observed between the rootstocks was consistent with the results obtained for excised roots, although the values were not exactly the same. It was also shown that the main root of Paulsen had greater contribution to ³ ⁶Cl⁻ uptake than lateral roots. ³ ⁶Cl⁻ fluxes by lateral roots were not significantly different between the rootstocks. Cl⁻ and Na⁺ distribution patterns in different root cell types were determined using the X-ray microanalysis technique. It was shown that Cl⁻ content in the hypodermis and cortical cells was higher than the other cell types in both rootstocks, but overall Cl⁻ content in the root of Paulsen was higher than K 51-40. The pericycle of the main root of Paulsen accumulated more Cl⁻ than K 51-40. It was concluded that Cl⁻ loading to the xylem was different in the rootstocks and Paulsen tended to prevent the xylem Cl⁻ loading process. Lateral roots also displayed opposite behaviour consistent with flux analysis. Membrane potential difference (PD) of the cortical cells showed a rapid and transient depolarization by adding 30 mM NaCl in both rootstocks that was followed by a gradual hyperpolarization. Depolarizations caused by 30 mM Choline-Cl, Na-MES and NaCl measured by the root surface potential method showed that Choline-Cl in K 51-40 and Na-MES in Paulsen caused greater depolarization than that of Na-MES in K 51-40 and Choline-Cl in Paulsen respectively. Assuming that PD measured in this method was the trans-root potential (TRP), it was concluded that the higher depolarization by Choline-Cl in K 51-40 can be due to higher Cl⁻ efflux rate to the xylem. Two different mechanisms were also detected for Cl⁻ transport: HATS which was observed in the range of 0.5-5 mM and a LATS in the range of 10-30 mM of the external NaCl concentration. This was consistent with the concentration dependence of Cl⁻ influx. In conclusion, evidence obtained from different experiments of this study indicated that in the grapevine rootstocks (Paulsen and K 51-40) Cl⁻ was mostly transported through the symplastic pathway. From ECl values determined for the rootstocks by the Nernst equation, a proton-driven transport system was responsible for Cl⁻ transport in both the HATS and LATS range of external NaCl concentrations. The rate of Cl⁻ transport from the root to shoot (xylem loading) was the major difference in Cl⁻ transport between the rootstocks in terms of salinity tolerance. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1339051 / Thesis (Ph.D.) -- University of Adelaide, School of Agriculture, Food and Wine, 2008

Soil salinity is one of the major abiotic stresses that decreases agricultural crop production through imposition of both ionic and osmotic stresses. The accumulation of Na⁺ and Cl⁻ in the cytosol to toxic levels inhibits metabolism. Unlike Na⁺, less is known about Cl⁻ uptake and transport in plants. Grapevine is moderately sensitive to salinity and accumulation of toxic levels of Cl⁻ in leaves is the major reason for salt-induced symptoms. In this study Cl⁻ uptake and transport mechanism(s) were investigated in two grapevine (Vitis sp.) rootstock hybrids differing in salt tolerance: 1103 Paulsen (salt tolerant) and K 51-40 (salt sensitive). Increased external salinity caused high Cl⁻ accumulation in shoots of the salt sensitive K 51-40 in comparison to Paulsen. Measurement of ¹ ⁵ NO₃⁻ net fluxes under high salinity showed that by increasing external Cl⁻ concentrations K 51-40 roots showed reduced NO₃⁻ accumulation. This was associated with increased accumulation of Cl⁻. In comparison to Paulsen, K 51-40 showed reduced NO₃⁻ / Cl⁻ root selectivity with increased salinity, but Paulsen had lower selectivity over the whole salinity range (0-45 mM). In order to examine if root hydraulic and permeability characterisations accounted for differences between varieties, the root pressure probe was used on excised roots. This showed that the osmotic Lpr was significantly smaller than hydrostatic Lpr, but no obvious difference was observed between the rootstocks. The reflection coefficient (σ) values (0.48-0.59) were the same for both rootstocks, and root anatomical studies showed no obvious difference in apoplastic barriers of the main and lateral roots. Comparing the uptake of Cl⁻ with an apoplastic tracer, PTS (3-hydroxy-5, 8, 10-pyrentrisulphonic acid), showed that there was no correlation between Cl⁻ and PTS transport. These results indicated that by-pass flow of salts to the xylem is the same for both rootstocks (10.01±3.03 % and 12.1±1.21 %) and hence pointed to differences in membrane transport to explain difference in Cl⁻ transport to the shoot. ³ ⁶Cl⁻ fluxes across plasma membrane and tonoplast of K 51-40 and Paulsen roots showed that ³ ⁶Cl⁻ influx in root segments of Paulsen was greater than K 51-40 over the first 10 minutes. Unidirectional influx within 10 min loading time showed increases with increases in the external concentrations in both rootstocks but Paulsen had higher influx rate when compared to K 51-40. This appeared to be due to a greater Vmax. There was no significant difference in Km. It was shown that ³ ⁶Cl⁻ accumulation and transport rate to the shoot of K 51-40 was higher than that of Paulsen. Compartmental analysis of ³ ⁶Cl⁻ efflux from intact roots confirmed that the difference in influx observed between the rootstocks was consistent with the results obtained for excised roots, although the values were not exactly the same. It was also shown that the main root of Paulsen had greater contribution to ³ ⁶Cl⁻ uptake than lateral roots. ³ ⁶Cl⁻ fluxes by lateral roots were not significantly different between the rootstocks. Cl⁻ and Na⁺ distribution patterns in different root cell types were determined using the X-ray microanalysis technique. It was shown that Cl⁻ content in the hypodermis and cortical cells was higher than the other cell types in both rootstocks, but overall Cl⁻ content in the root of Paulsen was higher than K 51-40. The pericycle of the main root of Paulsen accumulated more Cl⁻ than K 51-40. It was concluded that Cl⁻ loading to the xylem was different in the rootstocks and Paulsen tended to prevent the xylem Cl⁻ loading process. Lateral roots also displayed opposite behaviour consistent with flux analysis. Membrane potential difference (PD) of the cortical cells showed a rapid and transient depolarization by adding 30 mM NaCl in both rootstocks that was followed by a gradual hyperpolarization. Depolarizations caused by 30 mM Choline-Cl, Na-MES and NaCl measured by the root surface potential method showed that Choline-Cl in K 51-40 and Na-MES in Paulsen caused greater depolarization than that of Na-MES in K 51-40 and Choline-Cl in Paulsen respectively. Assuming that PD measured in this method was the trans-root potential (TRP), it was concluded that the higher depolarization by Choline-Cl in K 51-40 can be due to higher Cl⁻ efflux rate to the xylem. Two different mechanisms were also detected for Cl⁻ transport: HATS which was observed in the range of 0.5-5 mM and a LATS in the range of 10-30 mM of the external NaCl concentration. This was consistent with the concentration dependence of Cl⁻ influx. In conclusion, evidence obtained from different experiments of this study indicated that in the grapevine rootstocks (Paulsen and K 51-40) Cl⁻ was mostly transported through the symplastic pathway. From ECl values determined for the rootstocks by the Nernst equation, a proton-driven transport system was responsible for Cl⁻ transport in both the HATS and LATS range of external NaCl concentrations. The rate of Cl⁻ transport from the root to shoot (xylem loading) was the major difference in Cl⁻ transport between the rootstocks in terms of salinity tolerance. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1339051 / Thesis (Ph.D.) -- University of Adelaide, School of Agriculture, Food and Wine, 2008

AFRIKAANS: Die vraag onstaan of insette by aartappelproduksie deurentyds ekonomies optimaal gebruik word. Hierdie vraag word al hoe meer deur produsente gevra, veral waar die prysknyptang al hoe sterker gevoel word. Uit ‘n opbrengs oogpunt was stikstof nog altyd ‘n baie belangrike inset. Verliese aan opbrengste kan egter baie groot wees as stikstof ondoelmatig bespaar word. Om optimum stikstoftoedienings te kwantifiseer bly problematies. Die stikstofinhoud van die grond kan gemeet word, maar in hierdie studie is bewys dat die inligting uit hierdie ontledings dikwels misleidend en kan sinvolle aanbevelings nie altyd daarvolgens gemaak word nie. Aan die ander kant, kan die aartappelplant as indikator gebruik word. Die afgelope dertig jaar was baie aandag aan petioolsapekstraksie reg oor die wéreld gegee. Meeste navorsers versap die petiool en gebruik duur laboratorium toerusting om die NO3--konsentrasie te bepaal en maak dan daaruit afleidings. Met hedendaagse tegnologiese ontwikkelings, het vinniger ontledingstegnieke beskikbaar geword. Die Reflectoquant (Merck) is ‘n draagbare instrument wat gebruik word om die NO3--konsentrasie in die aartappelpetioolsap direk te meet. Met kalibrasie-proewe wat deur Omnia gedoen was, is ‘n optimale NO3--konsentrasie reeks (OPTI-reeks) opgestel waarmee stikstof bo-bemestings geskeduleer kon word. Die bepaalde OPTI-reeks is oor twee persele getoets. Die twee persele het verskil in grond tekstuur en ligging. Die Delmas perseel het ‘n hoër klei-inhoud gehad as die Bronkhorstspruit perseel. By die Bronkhorstspruit perseel het verskille tussen die behandelings gouer na vore gekom. Die persele wat laer vlakke van stikstof bemes was, en eerste stikstof bemes is het die laagste NO3--konsentrasie lesings gehad. By die Delmas perseel het hierdie tendens nie herhaal nie. In van die lesingtye het die laer stikstofbemestingsbehandelings hoër ontledings gehad. NO3--konsentrasie lesings, soos vermeld is in die meeste literatuur, het afgeneem oor tyd en gedui op ‘n verdunnings-effek van NO3--konsentrasie in die aartappelplant. Die verdunnings-effek kan toegeskryf word aan die fisiese verdunning van NO3- oor ‘n groter wordende plante, knolle en die gebruik van die NO3- in plantmetaboliese aktiwiteite. Opbrengste en bakkwaliteit van die onderskeie behandelings, was nie verlaag deur die OPTI-reeks te gebruik nie. As in ag geneem word dat ten minste, 45 kg ha-1 stikstof bespaar kon word deur gebruik te maak van die OPTI-reeks, is die metode ‘n baie kragtige ontledingstegniek om stikstof doelmatig te skeduleer. Stikstof sal nie die beperkende faktor in produksie wees, indien hierdie tegniek te gebruik word nie. ENGLISH: The question arises whether inputs are used optimally in an economical way for potato production. This is something that is asked more and more by producers. Nitrogen plays a dominating role in determining yield. Yield losses will be considerable if nitrogen is saved in an unnecessary way. To quantify optimum nitrogen applications can be difficult. Determining the nitrogen content of the soil can be one option, but as was shown in this thesis, this method can lead to incorrect nitrogen applications. The potato plant itself can be used as an indicator for nitrogen applications. For the past thirty years, a lot of emphasis has been placed on petiole sap analyses. Petioles were liquified and then expensive laboratory equipment were used to determine the NO3--concentration, whereafter the recommendations for nitrogen application were made. Analyses are made easier today with modern technological methods and equipment. Direct measurement of the NO3--concentrations in the potato petiole are possible by using the Reflectoquant (of Merck). Omnia Fertilizers conducted many experiments to determine an optimal NO3--concentration range (OPTI-range) to schedule nitrogen applications. In this study the OPTI-range was tested at two sites. The two sites differed in soil texture and district. The Delmas site has a higher clay percentage than the Bronkhorstpruit site. Quicker reactions on the treatments were found at the Bronkhorstspruit site. The plots that received lower nitrogen treatments, were fertilized first and had the lowest NO3--concentrations in the sap. This tendency was not replicated at the Delmas site. The lower nitrogen treatment plots sometimes had higher NO3--concentrations than the higher nitrogen treatments. NO3--concentration readings, as mentioned in most literature, declined over time and is explained by the diluting effect of nitrates in the plant. Not only is there an increase in the potato plants above ground growth, but tuber growth also constitute a big proportion of the biomass at the end of the growth period. Nitrogen is used in all these processes, which contribute to the diluting effect. Yield and tuber quality were not lowered by applying the OPTI-range. The OPTI-range is a good method to manage nitrogen requirements of the potato plant. At least 45 kg ha-1 nitrogen could be saved by using the OPTI-range. Therefore this is a powerful method to determine nitrogen scheduling. Nitrogen will not be the limiting factor in potato fertilization if the OPTI-range is used. / Dissertation (MSc(Agric))--University of Pretoria, 2010. / Plant Production and Soil Science / unrestricted

Orientador: Rogério Falleiros Carvalho / Resumo: O nitrogênio (N), elemento essencial ao crescimento e desenvolvimento vegetal, é absorvido principalmente como nitrato (NO3-). Esse elemento pode controlar a arquitetura de raízes e dessa forma favorecer a absorção de nutrientes pelas plantas. Para isso, tem sido mostrado que esses eventos estão relacionados ao controle hormonal, especialmente as auxinas, pois esse hormônio controla o crescimento das raízes de modo dependente de NO3-. Entretanto, esses mecanismos são complexos, pois dependem de várias moléculas, especialmente peróxido de hidrogênio (H2O2), o qual parece atuar nas sinalizações das auxinas em situações estressoras nas plantas, a exemplo da deficiência de N. Entretanto, a forma como auxinas e H2O2 interagem nas raízes sob deficiência de N foi pouco explorado. Assim, objetivou-se verificar se as auxinas dependem de H2O2 nas respostas das raízes de tomateiro à deficiência de NO3-. Para isso, plantas de da cultivar Micro-Tom de tomateiro foram cultivadas em hidroponia sob suficiência e deficiência de NO3-, ambas com presença e ou ausência de inibidor de transporte de auxinas, o (ácido 2,3,5-triiodo-benzóico- TIBA) e inibidor do acúmulo de H2O2 (Catalase). O delineamento experimental foi inteiramente casualizado, disposto em fatorial 2x4, com três repetições. Foi analisado comprimento e biomassa seca da parte aérea e biomassa seca, comprimento, área e volume das raízes. Além disso, foi quantificado conteúdo de MDA e H2O2. A deficiência de NO3- diminuiu o crescimento... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Nitrogen (N) is essential for plant growth and development, and is mainly absorbed as nitrate (NO3-). It also controls root architecture, improving plant nutritional status. These characteristics are related to hormonal control, especially by auxins. Auxins control root growth via NO3-dependent cell expansion, but these mechanisms are complex and depend on several molecules. Hydrogen peroxide (H2O2) appears to act on these auxins signalling in plant stress situations. However, how auxins and H2O2 interact in roots under N deficiency has not been well explored. Therefore, this study aimed to verify if auxins depend on H2O2 for responses of tomato roots to N deficiency. Micro-Tom plants were grown in hydroponic systems under sufficiency and deficiency of NO3-, both with and without auxin transport inhibitor, 2,3,5-triiodo-benzoic acid (TIBA), and the inhibitor of H2O2 accumulation (Catalase) in plants. The experiment was carried out in a completely randomized design in a factorial scheme (2x4) with three replications. Shoot length and dry biomass, as well as root dry biomass, length, area and volume were analysed. In addition, MDA and H2O2 content were also quantified. NO3- deficiency reduced shoot growth and, interestingly, promoted higher root growth. Furthermore, TIBA inhibited root growth under both NO3- conditions and the presence of catalase in NO3-deficiency resulted in lower root growth. These results show that auxins depend on H2O2 for tomato root responses to N defici... (Complete abstract click electronic access below) / Mestre

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The study employed Geographical Information System (GIS) technology to investigate the vulnerability of groundwater to NO3 content in Buncombe County, North Carolina in two different approaches. In the first study, the spatial distribution of NO3 contamination was analyzed in a GIS environment using Kriging Interpolation. Cokriging interpolation was used to establish how NO3 relates to land cover types and depth to water table of wells in the county. The second study used DRASTIC model to assess the vulnerability of groundwater in Buncombe County to NO3 contamination. To get an accurate vulnerability index, the DRASTIC parameters were modified to fit the hydrogeological settings of the county. A final vulnerability map was created using regression based DRASTIC, a statistic method to measure how NO3 relates to each of the DRASTIC variables. Although the NO3 concentration in the county didn’t exceed the USEPA standard limit (10mg/L), some areas had NO3 as high as 8.5mg/L.

The aim of the thesis was to prove the efficiency of aquatic plants in removing of water biogens, to produce a list of aquatic plants suitable for this purpose and laboratory verification of the selected plants which were monitored for pH, conductivity, total N, total P, ammonia nitrogen, nitrite nitrogen, nitrate nitrogen, plant growth capes and light intensity. Data obtained in experiments by laboratory measurements are processed into a graphic form and there are also available tables of measured values. Experiments were carried out in the classroom and anjanced laboratory building of the M Mendel University in the period from 17.6.2015 to 31.3. 2016. The selected plants for tests became duckweed (Lemna minor) and reed canary grass (Phalaris arundinacea). Tests were carried out in the length of 7 to 14 days for the duckweed and 7.5 months for the canary. Measured results confirmed the information obtained from other works and verified the results.