Submitted by (ana.araujo@ufrpe.br) on 2017-02-06T14:16:17Z No. of bitstreams: 1 Adriana Guedes Magalhaes.pdf: 1298691 bytes, checksum: 3170ed2d5c5bb5cad1f2320c4bf432db (MD5) / Made available in DSpace on 2017-02-06T14:16:17Z (GMT). No. of bitstreams: 1 Adriana Guedes Magalhaes.pdf: 1298691 bytes, checksum: 3170ed2d5c5bb5cad1f2320c4bf432db (MD5) Previous issue date: 2006-02-06 / Lettuce (Lactuca sativa L.) is the most cultivated vegetable in hydroponic system. This work aims to evaluate and characterize genotypes of lettuce grown under two levels of electric conductivity of nutrient solution, as well the genetic variability of these genotypes through the molecular markers of the type ISSR (Inter Simple Sequence Repeat. Four experiments were carried out using nutrient solutions with electric conductivity of 2.0 or 2.5 dS.m-1. Seeds were sown in phenolic foam plates and the seedlings were transferred for the nursling, on which they grew for 10 days receiving diluted nutrient solution. Then, they were transferred to polypropylene hydroponics channels measuring 50 mm of diameter on a growth bench for the initial growth. After 15 days the plants were transferred to others hydroponics channels measuring 75 mm of diameter on which they received the experimental treatments for more 15 days. Plant fresh weight, leaves fresh weight, root and stem fresh weight, stem length, number of leaves and tip-burning index were evaluated. Comparing the reaction of the cvs to the nutrient solutions with electric conductivity of 2.0 and 2.5 dS.m-1, the results showed that the tip-burning index for Babá de Verão and Forest was lesser for those grown on the nutrient solution of 2.0 than 2.5 dS.m-1. The total plant fresh weight and leaves fresh weight were greater for the plants grown on de nutrient solution with electric conductivity of 2.5 than 2.0 dS.m-1. The cvs Tinto, P-76 and P-78 presented higher tip-burning index on the nutrient solution of 2.5 dS.m-1, comparing to 2.0 dS.m-1. There was no significant difference on total plant fresh weight neither leaves fresh weight of the cvs Regina 2000, Tinto, P-44, P-85 and P-89, comparing the two nutrient solutions. For the study of the genetic variability thirty primers of ISSR were used. The data were interpreted with the aid of a matrix of genetic similarity after the construction of a dendrogram. Regarding all genotypes of lettuce studied, ten primers were amplified of a total of 134 fragments of DNA. The average of 13.4 fragments per primer was amplified and the size of fragments varied from 400 (UBC 842) to 2000 bp (UBC 808 and 857). The results showed that ISSR markers can be useful in the studies of genetic diversity of lettuce germplasm. / No sistema hidropônico, a alface (Lactuca sativa L.) é a hortaliça mais cultivada representando 80% da produção. Este trabalho teve como objetivo caracterizar e avaliar o comportamento de acessos de alface sob dois níveis de condutividade elétrica da solução nutritiva, bem como a variabilidade genética desses genótipos através de marcadores moleculares do tipo ISSR (Inter simple sequence repeat). Foram realizados quatro experimentos em dois níveis de condutividade elétrica da solução, 2,5 dS.m-1 e 2,0 dS.m-1. As sementes foram postas para germinar em placas de espuma fenólica e levadas, posteriormente, para a mesa de desenvolvimento, na qual receberam solução nutritiva durante 10 dias, quando foram transferidas para perfis de polipropileno com diâmetro de 50 mm, por mais 15 dias. Passado este período os tratamentos foram distribuídos no delineamento de blocos casualizados com repetições no tempo, em perfis de 75 mm de diâmetro, por mais 15 dias, totalizando o ciclo cultural de 45 dias. Avaliou-se o peso fresco das plantas inteiras, número de folhas, peso das folhas, índice de queima das bordas, comprimento do caule e peso do caule e raiz. Comparando a reação das cultivares, às soluções nutritivas com condutividade elétrica de 2,5 dS.m-1 e 2,0 dS.m-1, observou-se que o índice de queima das bordas das cvs. Babá de Verão e Floresta apresentou diferença, com menor percentual de queima na condutividade elétrica de 2,0 dS.m-1. Com relação ao peso fresco da planta inteira e peso das folhas frescas, as cultivares apresentaram diferenças significativas nas duas variáveis, obtendo os maiores pesos as alfaces cultivadas em solução nutritiva com condutividade elétrica de 2,5 dS.m-1. Comparando-se a reação dos acessos na condutividade elétrica de 2,5 dS.m-1 e 2,0 dS.m-1, observa-se que Tinto, P-76 e P-78 apresentaram alto índice de queima das bordas com a solução de 2,5 dS.m-1. Para o peso fresco da planta inteira e peso das folhas frescas, Regina 2000, Tinto, P-44, P-85 e P-89 não apresentaram diferenças significativas em relação aos dois níveis de condutividade. Para o estudo da variabilidade genética, foram utilizados trinta primers de ISSR. Os dados obtidos foram interpretados com o auxílio de uma matriz de similaridade genética e pela construção de um dendrograma. Destes, dez primers amplificaram um total de 134 fragmentos de DNA nos acessos de alface estudados. A média de fragmentos amplificados por primer foi de 13,4 e o tamanho desses fragmentos variou de 400 (UBC 842) a 2000 pb (UBC 808 e 857). Os resultados indicam que marcadores ISSR podem ser úteis em estudos de diversidade genética em germoplasma de alface.

Submitted by (lucia.rodrigues@ufrpe.br) on 2017-02-16T13:44:43Z No. of bitstreams: 1 Adriano Marcio Freire da Silva.pdf: 233973 bytes, checksum: 8365664074820b5955fb940c37b47616 (MD5) / Made available in DSpace on 2017-02-16T13:44:43Z (GMT). No. of bitstreams: 1 Adriano Marcio Freire da Silva.pdf: 233973 bytes, checksum: 8365664074820b5955fb940c37b47616 (MD5) Previous issue date: 2005-02-24 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Lettuce (Lactuca sativa L.) and Chinese cabbage (Brassica pekinnensis L.) may present yield reduction due to the occurrence of soft rot caused by Pectobacterium carotovorum subsp. carotovorum. Surveys of the intensity of soft rot in plantations of lettuce and Chinese cabbage were performed from January to May 2004 in mesoregions of the Zona da Mata and Agreste of the state of Pernambuco, Brazil. Disease prevalence of 45.2% was observed in lettuce and 100% in Chinese cabbage. The incidence of soft rot ranged from 0 to 22% in lettuce and 1 to 67% in Chinese cabbage. In lettuce higher intensity of soft rot was observed in areas: having more than 17 years of cultivation; planted with ‘Elba’, ‘Cacheada’ and ‘Tainá’; with clay soil type; irrigated by hosing and having poor drainage. Lower disease intensity was detected in areas: planted with ‘Verdinha’ and ‘Salad Bowl’; having coriander asprevious crop and when seedlings were produced in trays. In Chinese cabbage higher intensity of soft rot was found in areas having more than 10 years of cultivation, and in plantations with more than 50 days. The sole subspecies detected causing soft rot in all areas of lettuce and Chinese cabbage was Pectobacterium carotovorum subsp. carotovorum. To determine the ideal sample size for assessing incidence of soft rot in field, pilot-samples were conducted in eight lettuce planting areas and five Chinese cabbage planting areas, located in the main production municipalities in the state of Pernambuco. Based on our data and considering 20% of acceptable error, future surveys of the soft rot incidence should analyze 32 plots/ha and 20 plants/plot with 4.5m2 for lettuce and 21 plots/ha and 20 plants/plot with 10.5m2 for Chinese cabbage. For both crops there was significant correlation (P=0.05)between the intensity of disease aggregation and sample size but not between disease incidence levels and sample sizes / Os cultivos de alface (Lactuca sativa L.) e couve-chinesa (Brassica pekinnensis L.) podem ter a produção reduzida, devido à ocorrência da podridão-mole causada por Pectobacterium carotovorum subsp. carotovorum. No período de janeiro a maio de 2004, foram realizados levantamentos da intensidade da podridão-mole em plantios de alface e couve-chinesa, nas mesorregiões da Zona da Mata e Agreste do estado de Pernambuco. A prevalência da doença foi de 45,2% em alface e de 100% em couve-chinesa, enquanto a incidência variou entre 0 a 22% na primeira cultura e 1 a 67% na segunda. Em alface, maior intensidade da podridão-mole foi constatada em áreas: com mais de 17 anos de plantio; plantadas com as cultivares Elba, Cacheada e Tainá; com solo argiloso; irrigadas pelo sistema de rega e com drenagem deficiente. Por outro lado, menor intensidade da doença foi observada emáreas: plantadas com as cultivares Verdinha e Salad Bowl; cultivadas anteriormente com coentro e onde foram plantadas mudas produzidas em bandejas. Em couve-chinesa, observou-se que a intensidade da podridão-mole foi maior em áreas: com mais de 10 anos de cultivo e em plantios com mais de 50 dias. A única subespécie encontrada causando podridão-mole em todas as áreas de cultivo de alface e couve-chinesa foi Pectobacterium carotovorum subsp. carotovorum. Para a estimativa do tamanho ideal das amostras para avaliação da incidência da podridão-mole em campo, foram conduzidas amostragens-piloto em oito áreas de plantio de alface e cinco de couve-chinesa, situadas nos principais municípios produtores do estado de Pernambuco. Considerando os resultados obtidos e um erro aceitável de 20%, emfuturos levantamentos da incidência da podridão-mole, recomenda-se a amostragemde 32 parcelas/ha e 20 plantas por parcela de 4,5m2 para a alface e de 21 parcelas/ha e 20 plantas por parcela de 10,5m2 para a couve-chinesa. Para as duas culturas, houve correlação significativa (P=0,05) entre a intensidade de agregação da doença e o tamanho da amostra, mas não entre os níveis de incidência da doença e os tamanhos das amostras

Orientador: Arthur Bernardes Cecílio Filho / Banca: Braúlio Luciano Alves Rezende / Banca: Roberto Botelho Ferraz Branco / Resumo: O diagnóstico de problemas nutricionais, mediante a observação de sintomas, tem grande importância prática porque permite tomar decisões rápidas no campo para a correção das deficiências. O objetivo do trabalho foi descrever e fotografar os efeitos das omissões de cada macronutriente em cultivares de alface. O experimento foi conduzido em hidroponia, técnica do fluxo laminar de nutrientes, na UNESP, Câmpus de Jaboticabal, no Estado de São Paulo. Foram avaliados sete tratamentos: solução nutritiva completa, e as omissões de N, P, K, Ca, Mg e S, em delineamento experimental de blocos ao acaso, com três repetições. Os tratamentos com omissão de P, Ca e S na solução nutritiva foram aplicados no mesmo dia do transplante das mudas de alface do "berçário" para os canais de crescimento final. Quatro dias após foram aplicadas as soluções com omissão de N, K e Mg. Os sintomas visuais de deficiências, nas condições experimentais, surgiram na seguinte ordem de ocorrência: N, K, Mg, P, Ca. A omissão de enxofre não proporcionou sintomas visuais de carência no nutriente. Entre as cultivares, a visualização dos sintomas de carência nutricional foram facilmente visualizados em Verônica e Lucy Brown e dificilmente identificados na Oak Leaf Red Pixie / Abstract: Diagnosis of nutritional problems through observation of symptoms has great practical importance because it allows making quick decisions in the field for correction of deficiencies. This study aimed to describe and photograph the effects of macronutrient omission in lettuce cultivars. Seven treatments were evaluated: complete nutrient solution and the omission of N, P, K, Ca, Mg and S in randomized blocks design with three replications. Treatments were applied to cultivars Oak Leaf Red Pixie (crisp group without head, reddish leaves), Lucy Brown (American group, smooth, green leaves) and Veronica (crisp group without head, green leaves). Treatments with the omission of Ca, P and S in nutrient solution were applied on the same day that the lettuce seedlings were transplanted from "nursery" to the channels of final growth. After four days, it were applied the solutions with the omission of N, K and Mg. Visual symptoms of deficiency under the experimental conditions appeared to occur in the following order: N, K, Mg, P and Ca. The omission of S did not show the visual symptoms of nutrient deficiency. Among the cultivars, the symptoms of nutritional deficiency were easily observed in 'Veronica' and 'Lucy Brown' and hardly identified in the 'Red Oak Leaf Pixie / Mestre

Nas últimas duas décadas a produção de alimentos utilizando menos insumos sintéticos tem atraído a atenção em muitos campos, como indústria e pesquisa. Esta forma de produção é conhecida como agricultura orgânica e enaltece a ausência de produtos químicos industrializados no sistema produtivo agropecuário. Uma prática útil e de baixo custo é o emprego de biofertilizantes, principalmente pelo fato da crescente procura por tecnologias de produção que apresentem redução de custos e uma melhora na qualidade de vida. Esses fatos, contudo, têm incentivado pesquisadores e produtores rurais a experimentarem biofertilizantes preparados a partir da digestão aeróbia ou anaeróbia de materiais orgânicos em substituição aos fertilizantes minerais. Biofertilizante é a designação dada ao efluente líquido obtido da fermentação aeróbia ou anaeróbia da matéria orgânica e água, cujo produto final contém células vivas ou latentes de microrganismos. Assim, neste trabalho, os biofertilizantes foram preparados a partir dos resíduos orgânicos em quatro misturas (esterco bovino + bagaço de laranja (M1); cama de frango + bagaço de laranja (M2); esterco bovino + cama de frango (M3) e esterco bovino + cama de frango + bagaço de laranja (M4), que foram caracterizados em diversas etapas quanto à acidez, condutividade elétrica, concentração de macro e micronutrientes, teor de matéria orgânica e de substâncias húmicas, atributos de qualidade sanitária (coliformes termotolerantes, totais e E. colli) dentre outros e foi testado o potencial agronômico de biofertilizantes associados ao sistema convencional de manejo e a técnica do cultivo hidropônico, com o objetivo de contribuir para o menor consumo de reservas naturais de nutrientes do planeta. Os resultados mostraram que a mistura M3 produziu o melhor biofertilizante por obter os melhores resultados biométricos quando aplicado à cultura, demonstrando que foi possível a produção de um bom biofertilizante em relação ao potencial agronômico. / In the last two decades, there has been a worldwide trend in producing food using less synthetic inputs. This form of production is known as organic agriculture and it praises the absence of industrialized chemicals in the agricultural production system. A useful and low-cost practice is the use of biofertilizers, mainly due to the growing demand for production technologies that reduce costs and provide a better quality of life. However, those facts have encouraged researchers and farmers to experiment biofertilizers prepared from aerobic or anaerobic digestion of organic materials instead of mineral fertilizers. Biofertilizer is the name given to the liquid effluent obtained from aerobic or anaerobic fermentation of organic material and water, and the final product contains live cells or latent microorganisms. In this work, the biofertilizers were prepared from the organic residues in four mixtures (cow manure + orange bagasse (M1), poultry + orange bagasse (M2), cow manure + poultry (M3) and cow manure + poultry + orange bagasse (M4)), which were characterized in several stages regarding acidity, electrical conductivity, concentration of macro and micronutrients, organic material and humic substances content, antibacterial activity (thermotolerant coliforms, total and e-coli) among others, to test the agronomic potential of biofertilizers associated with the conventional management system and the hydroponic cultivation technique, in order to contribute to a lower consumption of natural nutrients reserves from the planet. The results showed that the mixture M3 produced the best biofertilizer, because of the biometric results when it was applied to the crop, demonstrating to be a successful biofertilizer in terms of agronomic potential.

Muitas vezes, a agricultura extensiva falha sob as condições semi-áridas da região Nordeste do Brasil, onde há escassez de águas superficiais e as chuvas são irregulares. O uso de águas subterrâneas poderia melhorar a produtividade das culturas. Mas, devido à condição geológica, é freqüente a ocorrência de águas subterrâneas salobras. A utilização dessas águas levaria à salinização do solo. Além disso, os poços perfurados têm baixas vazões. Nesse cenário, a hidroponia pode ser condizente à produção intensiva, baseada em pequenas áreas. A eficiência do uso da água na hidroponia é reconhecidamente maior que no solo porque torna mínima a perda por evaporação. Além disso, a hidroponia poderia aumentar a tolerância das culturas à salinidade. Isso permitiria o uso de águas salobras e, como benefício extra, incrementaria a proteção ambiental. Em hidroponia, não há o potencial mátrico que leva à diminuição da energia livre da água. Também, a própria estrutura funciona como sistema de drenagem. Os sais acumulados ao final do processo produtivo podem ser facilmente dirigidos para fora do sistema. Com essa hipótese, foram conduzidos experimentos para avaliar a tolerância da alface (cultivar Verônica) à salinidade em hidroponia e em solo. Foi construída uma estrutura experimental (40 parcelas independentes) para simular o cultivo na técnica do fluxo laminar de nutrientes (NFT). Para o cultivo em solo, foram utilizados vasos de 12 L e mulch plástico. Foi observado que na hidroponia NFT é possível empregar águas mais salobras que no cultivo em solo. Quando se têm disponíveis água doce e salobra, pode ser mais interessante usar água doce no preparo da solução nutritiva e água salobra na reposição ao volume consumido. O uso de água salobra para o preparo da solução nutritiva e da água doce para a reposição ao consumo produziu maiores perdas relativas sobre o rendimento do que a salinização gradual. Esse resultado foi proporcionado pela precocidade da alface. Em relação à tolerância, a salinidade limiar da alface 'Verônica' cultivada em hidroponia NFT foi estimada em 4,03 dS m-1. Sob as mesmas condições experimentais, a tolerância em solo foi estimada em 2,51 dS m-1. Esses resultados confirmam a hipótese levantada e permitem apresentar uma alternativa agrícola condizente à realidade de muitas famílias isoladas no semi-árido brasileiro. / Several times, the extensive agriculture fails under semi-arid conditions in the Northeast region of Brazil, where the surface water is shortage and the pluvial precipitation is irregular. The use of groundwaters could increase the crops yield. However, due to the geological factors, it is usual the occurrence of brackish groundwaters in this region. The utilization of these waters would carry to soil salinization. Moreover, the opened deep tubewells often have low capacity. In this scenario, the hydroponics systems may be suitable to intensive production based in reduced areas. The higher water use efficiency in soilless cultivation is a well reported advantage, because in this system the water loss by evaporation is minimum. In hydroponics systems could be increase the crop salt tolerance. This would permit the brackish water use and, as an extra benefit, would increase the environmental safety. In hydroponics system, there is no the matric potential, which decreases the free-energy of water. Furthermore, the hydroponics structure operates as a drainage system. The accumulated salts, at the end of the period, may be easily removed from system. In order to test this hypothesis, were carried out experiments to evaluate the lettuce (cv. Verônica) salt tolerance under soil and hydroponics conditions. It was constructed a structure (40 independent experimental units) to simulate the Nutrient Technique Film (NFT) cultivation. For the soil experiment, it was used 12 L recipients and plastic mulch. It was registered that is feasible use waters more brackish in NFT system than in soil. For available of brackish and nonsaline waters, it was more productive to use non-saline water to prepare the nutrient solution and brackish water to supply the water consumption. Higher yield losses were observed with the use the brackish water to prepare nutrient solution and the non-saline water to replace the water consumption. The nutrient solution salinization was less depreciative to yield than the constant salinity. This finding was providing by the lettuce precocity. In relation to the salt tolerance in NFT system, the lettuce salinity threshold was estimated in 4.03 dS m-1. Under the same experimental conditions, the tolerance in soil was estimated in 2.51 dS m-1. These results confirmed the hypothesis and permit to present an agricultural alternative suitable to reality of many isolated families in Brazilian semi-arid.

Nas últimas duas décadas a produção de alimentos utilizando menos insumos sintéticos tem atraído a atenção em muitos campos, como indústria e pesquisa. Esta forma de produção é conhecida como agricultura orgânica e enaltece a ausência de produtos químicos industrializados no sistema produtivo agropecuário. Uma prática útil e de baixo custo é o emprego de biofertilizantes, principalmente pelo fato da crescente procura por tecnologias de produção que apresentem redução de custos e uma melhora na qualidade de vida. Esses fatos, contudo, têm incentivado pesquisadores e produtores rurais a experimentarem biofertilizantes preparados a partir da digestão aeróbia ou anaeróbia de materiais orgânicos em substituição aos fertilizantes minerais. Biofertilizante é a designação dada ao efluente líquido obtido da fermentação aeróbia ou anaeróbia da matéria orgânica e água, cujo produto final contém células vivas ou latentes de microrganismos. Assim, neste trabalho, os biofertilizantes foram preparados a partir dos resíduos orgânicos em quatro misturas (esterco bovino + bagaço de laranja (M1); cama de frango + bagaço de laranja (M2); esterco bovino + cama de frango (M3) e esterco bovino + cama de frango + bagaço de laranja (M4), que foram caracterizados em diversas etapas quanto à acidez, condutividade elétrica, concentração de macro e micronutrientes, teor de matéria orgânica e de substâncias húmicas, atributos de qualidade sanitária (coliformes termotolerantes, totais e E. colli) dentre outros e foi testado o potencial agronômico de biofertilizantes associados ao sistema convencional de manejo e a técnica do cultivo hidropônico, com o objetivo de contribuir para o menor consumo de reservas naturais de nutrientes do planeta. Os resultados mostraram que a mistura M3 produziu o melhor biofertilizante por obter os melhores resultados biométricos quando aplicado à cultura, demonstrando que foi possível a produção de um bom biofertilizante em relação ao potencial agronômico. / In the last two decades, there has been a worldwide trend in producing food using less synthetic inputs. This form of production is known as organic agriculture and it praises the absence of industrialized chemicals in the agricultural production system. A useful and low-cost practice is the use of biofertilizers, mainly due to the growing demand for production technologies that reduce costs and provide a better quality of life. However, those facts have encouraged researchers and farmers to experiment biofertilizers prepared from aerobic or anaerobic digestion of organic materials instead of mineral fertilizers. Biofertilizer is the name given to the liquid effluent obtained from aerobic or anaerobic fermentation of organic material and water, and the final product contains live cells or latent microorganisms. In this work, the biofertilizers were prepared from the organic residues in four mixtures (cow manure + orange bagasse (M1), poultry + orange bagasse (M2), cow manure + poultry (M3) and cow manure + poultry + orange bagasse (M4)), which were characterized in several stages regarding acidity, electrical conductivity, concentration of macro and micronutrients, organic material and humic substances content, antibacterial activity (thermotolerant coliforms, total and e-coli) among others, to test the agronomic potential of biofertilizers associated with the conventional management system and the hydroponic cultivation technique, in order to contribute to a lower consumption of natural nutrients reserves from the planet. The results showed that the mixture M3 produced the best biofertilizer, because of the biometric results when it was applied to the crop, demonstrating to be a successful biofertilizer in terms of agronomic potential.

The extent and nature of physio-chemical changes that take place in detached leaves after harvest and during storage have been reviewed and discussed by Osborne (1962) and Rogers (1955). These changes include loss of moisture (Wittwer et al., 1962), chlorophyll degredation (Person et al., 1957), Protein loss (Thimann and Manmahan, 1960), and result in subsequent appearance of the visual manifestations of senescence of plant tissues. As lettuce, like most leafy vegetables, deteriorates rapidly and steadily after harvest. Loss of quality is inevitable and can only be minimized by rapid handling and with the best possible storage conditions (Pratt et al., 1954). In recent years, abundant work has been done to delay senescence by the use of various chemicals. Among the investigated chemicals, kinetin (6-furfurylarninopurine) and its related c ompounds show some promise. Van Overbeek et al. (1941) reported a potent new growthpromoting factor (kinetin) in coconut milk. This chemical is active in causing many of the growth reactions of c oconut milk at exceedingly small dosages. Subsequently several arninopurine compounds were synthesized. One of which is SD 4901 (Verdan), N6-benzyladenine, an experimental senescence inhibitor, was developed by Shell Development Company, Modesto, California in 1960. Many reports showed that this chemical is capable of delaying senescence of plant tissues on the basis of restoring protein molecules and respiration inhibition. On the other hand, others have shown stimulation of respiration and delaying of senescence. Paucity of scientific literature on the stability of those chemicals on leafy vegetables gave impetus to a study of the comparative influence of pre- and post-harvest applications of 6-furfurylaminopurine and N6-benzyladenine as related to successive harvest times. Such studies may have considerable economic bearing upon storing and shipping leafy vegetables to distant markets. This thesis presents effects of different concentrations (5, 10, and 20 ppm.) of pre- and post-harvest applications of 6-furfurylaminopurine and N6-benzyladenine as related to three successive harvest times (at one week intervals) on chlorophyll content, moisture content, total nitrogen, insoluble and soluble nitrogen, oxygen uptake, 0 and co2 production during storage (at 40 Fo and 85 percent RH) of "Great Lakes" variety of lettuce.

No description available.

This thesis examines the growth response and inter-relationships between shoots and roots of plants grown in compact soil. In the field, two topsoil and two subsoil conditions were created with five vegetable crops sequentially grown. Between 6 and 12% of the root system grew in the compact subsoil, which had a soil strength of 3.1 c.f. 1.9 MPa in the loosened subsoil. Both the root length density (Lv) and the specific root length were lower in the compact subsoil (80% and 30%, respectively). This had no effect on shoot growth when water and nutrients were well supplied. Compensatory root growth in the lose soil above the compact subsoil occurred in broccoli plants. As a result plants grown in soil with or without a compact subsoil had a similar total root length but with altered root distribution. When the water and nitrogen supplied to the soil was reduced, the lower subsoil Lv in the compact subsoil did not restrict water or N acquisition. This was possibly due to a large increase in the specific uptake per unit length of root, by the fewer roots in the compact subsoil. Compared to the subsoil treatments, only small changes in topsoil physical properties occurred when tillage was ceased. From the field trials the proportion and time of root growth into compact soil appeared important in determining the plant response. In a series of split-root experiments (horizontal and vertical arrangements of compact and loose soil) compensatory root growth in the loose soil only occurred when the root system was exposed to horizontally compact soil When compensatory root growth did not occur shoot growth was reduced. This resulted in there being a close relationship between total root length and leaf area. Further test results support a direct effect of mechanical impedance on shoot growth with a rapid (within 10 minutes) and large (50%) reduction in leaf elongation occurring when roots were mechanically impeded. In the field only plants whose roots were totally exposed to compact soil had reduced shoot growth with very compact subsoil having no effect. / Doctor of Philosophy (PhD)

The hypothesis that inoculation of transplants with vesicular-arbuscular mycorrhizal (VAM) fungi before planting into saline soils would alleviate salt effects on growth and productivity was tested on lettuce (Lactuca sativa L.) and onion (Allium cepa L.). A secondary hypothesis was that the fungi isolated from a saline soil would be more effective than those from a nonsaline soil. VAM inocula from a high-and a low-salt soil were trap-cultured, their propagules quantified, adjusted, and added to a pasteurized growth medium in which seeds germinated and seedlings grew for a few weeks. These seedlings, once colonized by VAM fungi, were transplanted into saline soil. Seedlings were exposed to high concentrations of NaCl at the time of transplant; in this respect, our technique aimed to simulate conditions of high salinity prevalent in soils affected by NaCl. Preinoculated lettuce and onion transplants grown for 10 weeks had increased shoot biomass compared with nonVAM plants at all salinity (NaCl) levels tested. Leaves of VAM lettuce at the highest salt level were significantly greener than those of the nonVAM lettuce. NonVAM onions were stunted due to available P deficiency in the soil, but inoculation with VAM fungi alleviated P deficiency and salinity effects except at the highest salinity level; nevertheless, VAM onions were significantly larger at all salinity levels. Increasing the level of available P by weekly applications to nonVAM plants partially alleviated the salinity effects on onion growth. VAM fungi from the saline soil site were not more effective in ameliorating the reduction on plant growth caused by salt than those from the nonsaline site. Colonization of roots and length of soil hyphae produced by the test fungi decreased with increasing salt. Results indicate that preinoculation of transplants with VAM fungi can effectively alleviate deleterious effects of saline soils on crop productivity. / Graduation date: 2000