Switchgrass (Panicum virgatum L.) is a warm-season perennial bunchgrass native to North America. In addition to its importance as a forage grass, it has promise as a biofuel crop. However, its use is limited because the grass is difficult to establish. Improving seedling vigor is one approach for improving establishment. The objectives of this study were to: 1) select for increased seedling mass through half-sib family selection; 2) calculate an estimate of heritability for seedling mass; and 3) determine the mode of pollination of switchgrass. One cycle of selection was completed using a half-sib methodology. Seedling mass was determined in a series of growth chamber studies. The seed was produced in different space planted field nurseries in the College Station, TX area. Mean seedling weight of the base population (C0) was 0.014 gm seedling-1, while the mean seedling weight from the C1 cycle of selection was 0.029 gm seedling-1. Unfortunately, bulked seed from the base population was old and did not germinate well. Therefore, a new base population was recreated, and the C0 seedlings from this population were heavier than the C1 seedlings, 0.020 and 0.016 gm seedling-1, respectively. The calculated heritability estimate was H2 = 0.6. Since the C0 and C1 nurseries were not grown on the same soil type, the lack of a positive response for seedling weight may be due to the different soil types. However, it may require another cycle of selection to determine if seedling mass can be positively impacted via half-sib selection. The mode of pollination of the species was determined by 1) observing pollen germination and tube growth in the pistils using fluorescent microscopy and 2) determining seed set with selfed plants. When self-pollinated, the pollen tubes never grew into the ovaries but when cross-pollinated the tubes readily grew to the micropyle. Also, when switchgrass plants were self-pollinated, viable seed were not produced. These findings indicate that switchgrass is highly self-sterile because a self-incompatibility mechanism prevents the pollen tubes from growing into the ovary of the same genotype.

The increasing world population is putting pressure on global food production. Agriculture must meet these growing demands by increasing crop yields. One phenomenon which prevents seedling emergence and damages crop yield is soil crusting. Understanding of soil crusting and the factors which influence it is fundamental to ensuring good crop production. An instrument which will test soil crust strength in a novel way, mimicking seedling growth, may lead to pre-emptive agricultural soil management which could increase crop production. This work details the process of design, construction and testing of an ascending penetrometer to measure soil crust strength. The full design process is discussed from concept generation and evaluation, using experimental methods and a multi-criteria decision making tool, through to final design configuration, specification, manufacture and testing. Traditionally, soil penetrometers measure soil strength by forcing a probe from the surface of the soil into the bulk soil below. To more accurately measure the direct impedance a seedling would experience a device should measure impedance from the bulk soil upwards and into the soil crust, mimicking what a growing seedling would experience. Results prove that the manufactured ascending penetrometer with a force resolution of 0.01N and displacement resolution of 0.0004mm is capable of detecting differences in soil crusts. At these resolutions and accuracy to 0.1N and 0.1mm excellent repeatability was achieved. The machine is therefore a useful and realistic tool for quantitatively comparing soil crusts in soil. It is hoped that being able to compare soil crust strength will lead to improved soil management techniques.

No description available.

Many studies have reported deficient or intermittent patterns of natural regeneration in temperate deciduous woodland. The present study aimed to assess the relative impact of herbivore-mediated plant mortality on the natural regeneration dynamics of representative tree species (Acer pseudoplatanus, Betula pendula, Fraxinus excelsior, Ilex aquifolium, Sorbus aucuparia, Taxus baccata and Ulmus glabra) in representative temperate deciduous woodland (Shipley Wood and Derwent Gorge, County Durham). Sapling density and the density, spatial association and size distribution of adult tree populations varied significantly between tree species and study sites, reflecting contrasting patterns of current and historical regeneration. Rates of post-dispersal seed predation and seedling herbivory were quantified using field-based 'cafeteria' trials. Rodents were the principal agents responsible for seed predation, whereas seedling herbivory was attributable to a mixed suite of herbivores including invertebrates, rodents and larger mammals. Rates of seed predation and seedling herbivory varied significantly between tree species, most likely reflecting individualistic, trade-off responses to chemical and physical attributes. Fine-scale spatial variation most likely reflected the preferential foraging of rodents beneath protective vegetation cover. There was no consistent evidence to support the hypothesis that dispersed seeds may escape disproportionately high offspring mortality beneath parent plants resulting from increased herbivore activity. Natural seedling density varied significantly between years and between tree species, according to the abundance of viable seeds produced by conspecific adult trees. Although seedling survivorship varied significantly between species, the survivorship of each species was similar between years and between cohorts of the same year. Canopy cover, field layer cover or correlated factors were significant determinants of seed germination and seedling emergence, establishment and survival, according to age- and species-specific tolerances. In relative terms, patterns of natural regeneration were primarily herbivore- limited (Acer and Taxus), microsite-limited (Betula, Fraxinus, Ilex and Ulmus) or limited by herbivores and microsites (Sorbus). The availability of viable seeds may have also limited the recruitment of Ilex, Sorbus, Taxus and Ulmus. Vegetative expansion, mast seeding, seed bank regeneration and repeated, prolonged reproduction may have reduced the actual impact of herbivory on natural regeneration, such that long-lived iteroparous tree species were unlikely to have been critically dependent on current recruitment.

No description available.

[Abstract]Crown rot, caused by Fusarium pseudograminearum (Fpg), is an important soilborne disease of wheat and barley. The degree of crop damage depends on seasonal conditions. Typically, high moisture conditions early in the season encourage seedling infection from stubble residues. Moisture stress later in the season leads to the production of unfilled “whiteheads”. Current control relies on cultural practices and sowing of partially resistant varieties. In order to understand the nature of partial resistance, I have examined the patterns of disease symptom development and pathogen spread in susceptible and partially resistant tissues of both pot-grown wheat, barley and oat seedlings and field-grown inoculated wheat trials. Further research was conducted to determine whether differences in pathogenicity occur amongst a small subset of Australian Fpg isolates. Seedling experiments confirmed that differences in disease ratings between susceptible and partially resistant genotypes are detected in younger leaf sheaths of older seedlings. At later harvest times differences between these genotypes are not significant in older leaf sheaths. Re-isolation of Fpg from inoculated seedlings has shown that each tissue was infected later in partially resistant genotypes compared to susceptible ones with a significantly lower number of isolations recorded at each harvest time in 42 day old seedlings. Barley cultivars were rapidly infected by the pathogen and exhibited high levels of disease symptoms. By comparison levels of infection in oats were low compared to all other genotypes. No significant differences between genotypes were observed in coleoptile tissues, either in fungal colonisation or development of disease symptoms. Disease development in the subcrown internode varied between lines/cultivars but was not representative of the relative susceptibility of each genotype. The pathogen did not appear to invade plant tissue via the vascular system but rather spread directly across the stem from leaf sheath to leaf sheath. Field trials were designed to study disease symptom development and localisation of Fpg hyphae in all expanded tissues (excluding head and roots) in wheat genotypes of known susceptibility to crown rot. Plants were harvested at approximately fortnightly intervals throughout the growing season. The main effects and interactions of harvest, genotype and tiller on each plant part were examined with a detailed statistical analysis of differences seen in these factors between susceptible and partially resistant wheat genotypes, in two inoculated field trials. While differences between genotypes were mostly not significant at each harvest when disease rating or isolations from leaf sheath tissues were examined, important differences between susceptible and resistant genotypes were seen in disease developments and Fpg infections of stem tissue in field trials. Restriction of pathogen growth and symptom development was more pronounced in the tissues of 2-49 (possesses seedling resistance) than in the field resistant Sunco. At present, the mechanisms that lead to these resistance responses are unknown. The pathogenicity study aimed to determine whether 7 Fpg isolates and a mixed inoculum differed in ability to cause crown rot in 9 wheat genotypes ranging in susceptibility to this disease. Although a genotype*inoculum interaction was significant, there is no evidence of stable pathogenic races in the isolates examined in these experiments. The growth of all isolates was partially inhibited in a consistent manner on resistant genotypes when compared to very susceptible genotypes. These results confirm significant differences in the aggressiveness of Fpg isolates on wheat, evidenced by variation in mean disease severity between isolates growing on a range of host genotypes.

O emprego de práticas adequadas na implantação do vinhedo, principalmente o uso de mudas enxertadas com boa sanidade, é fator essencial para o sucesso da viticultura no Brasil e, em especial, no Sudoeste do Paraná. O objetivo do trabalho foi testar temperatura de estratificação, tipo e época de enxertia para produção de mudas da cultivar Bordô/Paulsen 1103 por enxertia de mesa com estratificação. Para isso foram implantados três experimentos. No primeiro e no segundo experimentos, as estacas do porta-enxerto foram tratadas com ácido indol-butirico (AIB) antes e após a estratificação, respectivamente. Ambos os tratamentos foram realizados em delineamento experimental de blocos ao acaso, em esquema fatorial de 3 x 2 (temperatura de estratificação x tipo de enxertia), com quatro repetições e dez unidades de observação (estacas enxertadas). O fator temperatura de estratificação teve os níveis 19, 24 e 29 °C e o fator técnica de enxertia foi com garfagem de topo manual e “tipo ômega” com auxílio de alicate especial. O terceiro experimento foi realizado em delineamento experimental blocos ao acaso, em esquema fatorial 4 x 2 (época de enxertia x temperatura de estratificação), com quatro repetições e 20 unidades unidades de observação por parcela. O fator épocas de enxertia foi composto pelos meses de coleta (maio, junho, julho e agosto) e o fator temperatura de estratificação, em dois níveis (19 e 24 ºC). Os experimentos foram conduzidos em condições controladas (BODs e em casa de vegetação). As análises realizadas na saída da estratificação (21 dias após a realização da enxertia) foram a percentagem de formação de calo na região da enxertia e a brotação dos enxertos. Após a entrada na casa de vegetação até aos 70 dias, foi avaliado o desenvolvimento da brotação, com uso da escala fenológica, e a mortalidade das estacas. Aos 120 dias após a estratificação foram avaliados a sobrevivência final das estacas, o desenvolvimento do sistema radicial (número de raízes e matéria seca da raiz), desenvolvimento da parte aérea (área foliar, comprimento da brotação e matéria seca da brotação). A enxertia tipo garfagem de topo apresentou melhores resultados que a tipo ômega; as temperaturas de 19 e 24 ºC facilitam a sobrevivência do enxerto, sendo as mais indicadas para estratificação; o mês de julho é o mais recomendado para realização da enxertia de mesa com estratificação. / The use of appropriate practices in the implementation of a vineyard, especially the use of grafted cuttings with good health, is an essential factor for successful viticulture in Brazil and, in particular, Southweast Paraná. The objective of this work was to test stratification temperature, type and period of grafting, for the propagation of vines, 'Bordô'/'Paulsen 1103', by bench grafting cuttings with stratification. Three experiments were developed to test these objectives. In the first and second experiment, the cuttings of the rootstock were treated with indole-butyric acid (IBA) before and after estratification, respectively. Both treatments were conducted in a randomized block in a factorial 3 x 2 (estratification temperature x grafting type), with four replications and ten units of observation (grafted cuttings). The factor estratification temperature was 19, 24, and 29 °C, while the factor grafting technique either manual top grafting or "omega" with the aid of special pliers. The third experiment was performed in randomized blocks, in a 4 x 2 factorial design, with four replications and 20 units of observation. The factor A was different period of grafting (May, June, July, and August) and the factor B was stratification temperature at two levels (19 and 24 °C). The experiments were conducted under controlled conditions (in growth chambers and in the greenhouse). The parameters evaluated at the end of stratification (21 days after grafting) were: percentage of callus formation in the region of grafting and percentage of sprouting. In the greenhouse we evaluated the development of sprouting, from day one until day 70, using a phenological scale, and measuring cuttings mortality. One hundred and twenty days after stratification we evaluated the survival of the cuttings, the development of the root system (root number and dry weight of root), shoot growth (leaf area, shoot length and dry matter). Top grafting had a higher percentage of viable grafted cuttings than the “omega” technique; temperatures of 19 and 24 °C favored the survival of the graft; while July was the most recommended period for bench grafting with stratification.

Resumo: Plântulas de C. antisyphilitica (Mart.) Mart., T. chrysotricha (Mart. ex Dc.) Standl., T. heptaphylla (Vell.) Toledo, T. roseo-alba (Ridl.) Sand. e Z. tuberculosa (Vell.) Bur., espécies arbóreas conhecidas popularmente como ipês, foram estudadas morfo-anatomicamente, citogeneticamente e palinologicamente. As sementes estenospérmicas apresentam testa em variados tons de castanhos com alas hialinas, assimétricas, flexíveis e de textura papirácea. As plântulas são angiospermas, dicotiledôneas, fanerocotiledonares e epigéias. Os sistemas radiculares são axiais e ramificados. Tanto hipocótilos como epicótilos são verdes e podem apresentar ou não pêlos. Os cotilédones são foliáceos, reniformes, bilobados, clorofilados, peciolados e com recortes apicais profundos. Os eófilos são simples, simétricos, glabros ou pilosos, peciolados e de filotaxia oposta. Apresentam ápice obtuso ou acuminado, base cuneada e margem serreada. As estruturas vegetais apresentam epidermes simples, unisseriadas e pilosas. Geralmente, os cotilédones, os eófilos e os metáfilos são dorsiventrais, hipoestomáticos com estômatos anomocíticos. Os mesófilos cotiledonares são heterogêneos, exceto em Tabebuia heptaphylla onde é homogêneo. O hipocótilo pode ser considerado zona de transição por apresentar elementos vasculares em diferenciação. O epicótilo possui os feixes vasculares colaterais organizados. Os elementos traqueais internos ao córtex da raiz estão dispostos em forma de anel ao redor de uma medula parenquimática. Nos pecíolos dos metáfilos os feixes vasculares colaterais dispõemse em forma de anel, com exceção de C. antisyphilitica e T. heptaphylla onde mostram-se em forma de ferradura. Todas as espécies possuem 2n = 40 cromossomos, exceto em T. chrysotricha onde foram detectadas sementes poliembriônicas com 2n = 80 cromossomos...(Resumo completo, clicar no acesso eletrônico abaixo) / Abstract: Seedlings of C. antisyphilitica (Mart.) Mart., T. chrysotricha (Mart. ex Dc.) Standl., T. heptaphylla (Vell.) Toledo, T. roseo-alba (Ridl.) Sand. and Z. tuberculosa (Vell.) Bur., arboreal species popularly known as ipê, were morphoanatomically, cytogenetically and palinologycally studied. The estenospermic seeds have tegument in varied chestnut tones, with hyaline, asymmetric, flexible and paper texture expansions. The seedlings are angiosperm, dicotyledonous, phanerocotilar and epigeal. The root systems are axial and ramified. Both hypocotyll and epicotyll are green and can present pile or not. The cotyledons are foliaceous, kidney shaped, bilobe, chlorophyll, petiolate and with apical deep cuttings. The eophylls are simple, symmetrical, with or without pile, petiolate and of opposite phyllotaxy. They present obtuse or acuminate apex, cuneate base and sawed margin. The vegetable structures showed simple, unisseriate, pile epidermis. Generally the cotyledons, the eophylls and metaphylls are dorsiventral, hipostomatic, with anomocytic stomatal. The cotyledons mesophyll is heterogeneous, except the Tabebuia heptaphylla, within is homogeneous. The hypocotyll can be considered a transition zone by presenting vascular elements in differentiation. The epicotyll has organized collateral vascular bunches. The windpipe elements the root cortex is arranged in a ring around a parenquimatic medulla. In the petiolates of the metaphyll the collateral vascular bunches disposed is ring shaped, except the C. antisyphilitica and T. heptaphylla, where it is shown in a horseshoe shaped. All the species have 2n = 40 chromosomes, except the T. chrysotricha, where polyembryonic seeds with 2n = 80 chromosomes were detected. The chromosomes are small and present uniformity within the same karyotype...(Complete abstract, click eletronic address below) / Orientador: José Roberto Moro / Coorientadora: Fabíola Vitti Moro / Banca: Ricardo Machado da Silva / Banca: Herberte Pereira da Silva / Banca: Samira Miguel Campos de Araujo / Banca: Carlos Ferreira Damião Filho / Doutor

Made available in DSpace on 2014-06-11T19:23:08Z (GMT). No. of bitstreams: 0 Previous issue date: 2008-02-19Bitstream added on 2014-06-13T19:49:55Z : No. of bitstreams: 1 iwazaki_mc_me_botib.pdf: 1084974 bytes, checksum: fe5369f9a1f74a9fd163e3e8822d12a8 (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Mimosa Linnaeus é o gênero com maior número de representantes de Mimosoideae no cerrado, com 189 espécies registradas. É um gênero que exibe características morfoanatômicas, hábito e tipos de frutos variados. Mimosa daleoides Benth., M. dolens Vell. var. anisitsii (Lindm.) Barneby e M. orthacantha Benth. são arbustivas e de ocorrência comum em remanescentes do cerrado paulista, observadas como invasoras, e foram selecionadas para o presente trabalho. Os objetivos foram descrever morfologia, anatomia e ontogênese dos frutos e sementes; detalhar a morfologia das plântulas e a anatomia e venação de cotilédones e eofilos; e comparar as espécies entre si e com a literatura. O material coletado foi processado segundo técnicas usuais em microscopia óptica, utilizando inclusão em metacrilato, cortes em micrótomo de rotação e coloração com azul de toluidina; também foram confeccionadas lâminas semipermanentes para análise de maceração, diafanização e cortes a mão livre. O ovário das três espécies é curto-estipitado, com 3-5 óvulos anátropos, tendendo a campilótropos apenas em M. daleoides. Emergências se formam ao longo do desenvolvimento do fruto no pericarpo; o mesocarpo é parenquimático, com hipoderme externa e interna de M. dolens var. anisitsii e somente a interna de M. daleoides com células fenólicas. Um meristema adaxial se desenvolve, do qual deriva o endocarpo externo, lignificado no final da maturação, e endocarpo interno, parenquimático. Mimosa orthacantha exibe fibras e esclereídes de orientações opostas no endocarpo externo, diferenciando-se das demais. A partir da análise anatômica, pode-se concluir que os frutos formados são craspédios em M. daleoides e M. orthacantha, ligados ao eixo da inflorescência do tipo racemo na primeira e glomérulo na segunda, e legumes de deiscência passiva em M. dolens var. anisitsii,... / Mimosa Linnaeus is the genus of Mimosoideae most represented in the cerrado, with 189 recorded species. The genus exhibits varied morphological and anatomical characteristics, habits, and fruit types. Mimosa daleoides Benth., M. dolens Vell. var. anisitsii (Lindm.) Barneby, and M. orthacantha Benth. are shrubs that commonly occur in remnant areas of cerrado vegetation in São Paulo State and are often considered invasive plants. The present work describes the morphology, anatomy, and ontogeny of the fruits and seeds of this species, examines the morphology of the seedlings, the anatomy and venation of the cotyledons and eophylls, and compares the three species and information concerning them in the published literature. The plant material was processed according to traditional techniques in light microscopy, including embedding in methacrylate, sectioning in a rotary microtome, and staining with toluidine blue. Additionally, semi-permanent slides were prepared for maceration analyses, clearing leaves, and free-hand sections. The ovary of the three species is short-stipitate, with 3-5 anatropous ovules, tending towards a campylotropous only in M. daleoides. Emergences form in the pericarp during fruit development; the mesocarp is parenchymal, with an outer and inner hypoderm in M. dolens var. anisitsii but only an inner hypoderm with phenolic cells in M. daleoides. An adaxial meristem develops, from which the outer and inner endocarp are derived; the outer is lignified at maturation, and an inner is parenchymatous. Mimosa orthacantha demonstrates fibers and sclerids oriented in opposite directions in the outer endocarp, a characteristic that differentiates this species from the others. Anatomical analyses indicate that the fruits of M. daleoides and M. orthacantha are craspedia and are fixed to the inflorescence axis of the raceme ...(Complete abstract click electronic access below)

In Venezuela rainfall-induced crust is the main problem in obtaining adequate stands of sesame (Sesamwn indicum L.) The effectiveness of seven commercially available soil conditioners to prevent soil crusting and their influence on sesame seedling emergence was tested on Parlo silt loam. The chemicals were sprayed on the soil surface at different rates and dilutions . The rates were established to give about the same treatment cost. Two chemica 1 s: a polyviny 1 aJ cohol (El vanol 71-30) and an anionic asphalt emulsion (Humofina B-2864) gave the greatest increase in sesame seedling emergence. Thereafter, the two chemicals were tested on two Utah soils (Parlo silt loam and Nib l ey silty c l ay loam) and four Venezuelan soils. Three of the Venezuelan soils (Turen silt loam , Nontilled Turen silt loam, and Agua Blanca si lty clay l oam) were sampled in areas actually being used for sesame production, but with problems of soil crusting. TI1e fourth Venezuelan soil (Guanipa sand) was collected in an area where sesame has recently been introduced.