Thesis (M.S.)--Miami University, Dept. of Botany, 2006. / Title from first page of PDF document. Includes bibliographical references (p. 95-102).

Made available in DSpace on 2014-06-11T19:26:09Z (GMT). No. of bitstreams: 0 Previous issue date: 2007-05-03Bitstream added on 2014-06-13T18:29:33Z : No. of bitstreams: 1 lazaro_ccm_me_jabo.pdf: 257891 bytes, checksum: 15139254a062092c31e6dd0caf9ac250 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O objetivo deste trabalho foi avaliar a tolerância ao sombreamento de cinco variedades de Stylosanthes guianensis, em duas épocas de semeadura. Utilizou-se o delineamento inteiramente casualizado com quatro repetições e em três e quatro níveis de sombreamento. Aos 60 dias após o início de cada experimento foram avaliadas as características: altura de planta, número de ramos, de folhas e de nódulos, área foliar, teores de clorofila a e b, teor total de clorofila, razão entre os teores de clorofilas a/b, comprimento de raiz, massa seca de ramos, de folhas e de raiz. Nas duas épocas de avaliação, a variedade vulgaris cv. Pucallpa apresentou maiores valores para as características estudadas, sendo o melhor desempenho das variedades em 30% de sombreamento na primeira avaliação e em 50% na segunda. Os resultados obtidos indicaram que há variabilidade de resposta ao sombreamento entre as variedades de Stylosanthes guianensis. / The objective of this work was to evaluate the tolerance to the shading of five varieties of Stylosanthes guianensis, at two times of sowing. Treatments were set in complete randomized design with four repetitions, and three and four levels of shading. To the 60 days after the beginning of each experiment had been measured the traits: height of plant, number of branches, of leaves and nodules; leaf area; content of chlorophyll a and the b, total content of chlorophyll, reason enters contents of chlorophyll a/b, root length; dry mass of branches, of leaves and root. At the two times of evaluation, the variety vulgaris cv. Pucallpa had presented raised values for the studied traits, being the best performance of the varieties in 30% of shading in the first evaluation and 50% in second. The gotten results had indicated that it has variability of reply to the shading between the varieties of Stylosanthes guianensis.

Pendant la maturation des graines, la germination, tolérance à la dessication et longévité sont acquises de manière séquentielle. La maturation s’achève par la dessication qui amène l’embryon à l’état de quiescence. La maturité des graines à la récolte est le premier facteur qui in¿ uence la longévité et l’établissement de la culture lors du semis. On ne comprend pas comment la longévité est installée pendant la maturation et comment un séchage prématuré in¿ uence la longévité et la reprise des activités cellulaires pendant l’imbibition. L’objectif de la thèse était de répondre à ces questions en comparant les transcriptomes de graines immatures et matures de soja et Medicago truncatula pendant la dessication et l’imbibition. Les graines immatures furent récoltées après le remplissage avant la dessiccation, lorsque la longévité n’est pas encore acquise.Chez le soja, la comparaison des transcriptomes des graines immatures et matures montre que le séchage forcé n’est pas identique à la dessication in planta qui se caractérise par la synthèse de protéines chaperones. Plus de 89% des gènes différentiellement exprimés après 18 h d’imbibition présentent des pro¿ ls d’expression identiques dans les graines immatures et matures, en accord avec la germination comparable de celles-ci. L’analyse des transcrits dont la teneur augmente uniquement pendant l’imbibition des graines mature suggère la mise en place de mécanismes de réparation. La comparaison de ces données avec Medicago montre que l’imbibition des graines matures se caractérise par une sur-représentation des gènes liés au / During seed maturation, germination, desiccation tolerance and longevity are acquired sequentially. Seed maturation is terminated by a desiccation phase that brings the embryo to a quiescent state. Seed maturity at harvest in¿ uences seed longevity and crop establishment. After harvest, seeds are usually dried to water content compatible with long term storage and post-harvest treatments. However, there is a lack of understanding of how seed longevity is acquired during seed maturation and how premature drying impacts longevity and resumption of cellular activities during imbibition. This was addressed here by comparing transcriptome changes associated with maturation drying and imbibition of seeds of soybean and Medicago truncatula, harvested at an immature stage and mature dry stage.The immature stage corresponded to end of seed ¿ lling when longevity was not acquired while other vigor traits were acquired. Transcriptome characterization in soybean revealed that enforced drying was not similar to maturation drying in planta, which stimulated degradation of chlorophyll and synthesis of protective chaperones. Eighty-nine % of the differentially expressed genes during a 18h-imbibition period showed a similar pattern between immature and mature seeds, consistent with a comparable germination between stages. An analysis of the 147 transcripts that increased during imbibition of mature seeds but not in immature seeds suggested an activation of processes associated with shoot meristem development and DNA repair. These data were compared with imbibing immature and mature seeds

The tribe Podalyrieae is a diverse and interesting group with most of its species found in the Cape Floristic Region (120 out of 128 species), the smallest floral kingdom and the subject of intense conservation interest. DNA sequence data from nuclear ribosomal internal transcribed spacer, including the 5.8s coding region, were used to reconstruct the phylogeny of this Cape Floral Clade. Results support a transfer of Cadia (Sophoreae) to Podalyrieae. Cyclopia is well imbedded in a paraphyletic Podalyriinae and not sister to the tribe as previously suggested. A broader concept of Podalyrieae, which include Podalyriinae, Xiphothecinae and Cadia is suggested. Dating the nodes of the phylogenetic tree using non-parametric rate smoothing with a fossil calibration point indicates that the root node of Podalyrieae (+ Cadia) is 34.35MYA. / Dr. M. van der Bank

To predict the response of communities and ecosystems to rising levels of atmospheric CO2, the response of individual plants under natural conditions needs to be determined. Podalyria sericea, a fynbos legume, was grown in a greenhouse under ambient (35 Pa) and elevated (70 Pa) CO2 partial pressure for 18 months. Growth, leaf 615N and leaf gas exchange was measured to determine whether this N2-fixer could maintain a positive growth response under conditions of high competition. Results revealed a lack of positive growth response to elevated CO2, although far more flowers were produced in the elevated treatment. Allocation patterns were slightly different, with relatively higher shoot mass for plants exposed to elevated CO2. Leaf 61 5N and N concentrations were unaffected. Photosynthetic capacity was greatly reduced and maximum rates of Rubisco carboxylation (V cmaJ and light saturated electron transport (Jniax) were lower for plants exposed to elevated CO2. Net CO2 assimilation (A) at growth CO2 was higher for the plants from the ambient treatment. Shading appears to have been an important constraint on growth response to elevated CO2, and plants which received more light had significantly more biomass in the elevated treatment. The potential effect of restricted root growth and low soil nutrient availability are discussed as additional factors which may have negated a positive growth response.

Interseeding legumes in native warm-season grasses (NWSG) may improve the nutritive value of the stand, result in more consistent forage availability throughout the growing season, and increase forage yield. These benefits are often not realized due to difficulties in establishing legumes in existing NWSG stands. The objective of this study was to investigate the effect of planting method of legume interseeding, timing of legume interseeding, and the efficacy of burning plant residue on legume establishment in NWSG. Two forage legumes, 'Alice' white clover (Trifolium repens L.) and 'Freedom HR' red clover (Trifolium pratense L.), were interseeded into mixed 'Niagara' big bluestem (Andropogon gerardii Vitman), 'GA Ecotype' Indiangrass (Sorghastrum nutans Nash), and 'Camper' little bluestem (Schizachyrium scoparium) pasture in 2022 and 2023 at the Southern Piedmont AREC in Blackstone, Virginia. Planting method at three levels (no-till drill, broadcast, and non-planted control) were evaluated at three planting timing levels (fall planting, winter planting, and winter planting with burned residue). Among the treatment combinations, burned plots that were drilled resulted with the greatest spring clover count of 236 plants m-2, followed by winter drill (146 plants m-2) and burn broadcast (133 plants m-2). All fall plantings and all control plots were similar with a mean of 21 plants m-2. As a result of greater initial clover emergence, plots that were burned or seeded in the winter had greater clover content throughout the experiment; burned and drilled plots had over 90% clover ground cover throughout the second year. Domination of plots by clover in the second year caused yields and the proportion of NWSG in the stand to decline, with burned plots yielding 5,757 kg ha-1 compared to a winter-fall mean of 7,429 kg ha-1. Plots with greater clover content were able to sustain higher crude protein content and lower neutral detergent fiber content in both the establishment year and the second year. Though interseeding legumes benefitted nutritive values, these results suggest that red clover may be incompatible with the NWSG evaluated. Burned plots were especially affected by excessive competition. Further research is needed to evaluate forage legume species which complement NWSG in mixture rather than compete with them. / Master of Science / Interseeding legumes in native warm-season grasses (NWSG) may improve the nutritive value of the stand, result in more consistent forage availability throughout the growing season, and increase forage yield. These benefits are often not realized due to difficulties in establishing legumes in existing NWSG stands. The objective of this study was to investigate the effect of planting method of legume interseeding, timing of legume interseeding, and the efficacy of burning residue on legume establishment in NWSG. Two forage legumes, 'Alice' white clover (Trifolium repens L.) and 'Freedom HR' red clover (Trifolium pratense L.), were interseeded into mixed 'Niagara' big bluestem (Andropogon gerardii Vitman), 'GA Ecotype' Indiangrass (Sorghastrum nutans Nash), and 'Camper' little bluestem (Schizachyrium scoparium) pasture in 2022 and 2023 at the Southern Piedmont AREC in Blackstone, Virginia. Planting method at three levels (no-till drill, broadcast, and non-planted control) were evaluated at three planting timing levels (fall planting, winter planting, and winter planting with burned residue). Among the treatment combinations, burned and drilled plots produced more clover plants in spring at 236 plants m-2, followed by winter drill (146 plants m-2) and burn broadcast (133 plants m-2). All fall plantings and all control plots were similar with a mean of 21 plants m-2. As a result of greater initial clover emergence, plots that were burned or seeded in the winter had greater clover content throughout the experiment; burned and drilled plots had over 90% clover ground cover throughout the second year. Domination of plots by clover in the second year caused yields and the proportion of NWSG in the stand to decline, with burned plots yielding 5,757 kg ha-1 compared to a winter-fall mean of 7,429 kg ha-1. Plots with greater clover content were able to sustain higher crude protein content and lower neutral detergent fiber content in both the establishment year and the second year. Though interseeding legumes benefitted nutritive values, these results suggest that red clover may be incompatible with the NWSG which were evaluated. Burned plots were especially affected by excessive competition. Further research is needed to evaluate forage legume species which complement NWSG in mixture rather than compete with them.

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The competitive advantage of velvet beans as an economic agricultural commodity. In the past 40 years, although food insecurity, poverty and environmental degradation persist, worldwide farmers have made considerable progress in increasing per capita food production whilst better understanding natural-resource management. Literature indicates that — in the decades to come — food demand will both grow and change for three reasons, namely increased numbers of people, increased income (people will have more purchasing power), and increased urbanisation (people will be more likely to adopt new diets containing animal protein and cereal). The world population is expected to increase to 8,9 billion by 2050, with 84% in the developing countries. Food insecurity and malnutrition are expected to persist despite progress on average per capita consumption of food. As a complex system, and despite challenges, agriculture must produce simultaneously unprecedented abundance of food and unparalleled social concerns. As a business, agriculture requires high capital investments in land, facilities and production inputs; most often producing commodities of generally low unit value with thin profit margins, thereby forcing producers to strive for efficiency in all aspects of production. Therefore, it is of utmost importance that farmers should understand sustainable agriculture; where a more sustainable food-production system seeks to make the best use of nature’s goods and services whilst not being harmful to the environment. Sustainable agriculture should maximise the productivity of the land; should focus on locally adapted resource-conserving technologies which assist whole system redesign and large-scale adoption; and should aim to minimise the use of harmful non-renewable and fossil-fuel derived inputs. Fertilisers have not replaced the function of organic matter and other management practices; but soil erosion and toxic waste rather did increase disproportionately along with increased agricultural production. This has led to a progressive decline in crop and land productivity as a result of soil degradation, water contamination, increasing problems of weed infestation, pests and diseases. Often the apparent absence of sustainable productive agricultural systems within the scope of commercial farmers is not because of the lack in technology or low yield potential of traditional varieties, but rather on account of the limited knowledge or lack of awareness on the part of farmers about sustainable production practices which function in harmony with their farming environment. As one of the keys to success the velvet bean — which can grow almost everywhere — is an example of the introduction of a simple regenerative component into a farming system, as well as boosting the capacity of a farmer for local adaptation of the technology. Integrating the natural processes of nutrient cycling, nitrogen fixation and introducing natural enemies of pests into food production processes can contribute to minimising environmental damage and/or health of the farmer and the consumer. Using the knowledge and skills of farmers helps to improve their self-reliance and to solve a common management problem, such as social- and human-capital management. The velvet bean is seen as an answer to the agricultural problem of low nutrient supply to the staple crop of maize. The bean creates ground cover, regenerates, fertilises the soil, controls weeds and adds organic matter and nutrients. In arid South Africa the crop is one of the strongest defences of the farmer against the harmful effects of El Niño — with the bean protecting the soil, holding water and fertilising the land with its leaves. With the velvet bean farmers can grow their own organic and inexpensive fertilisers. Commercial fertilisers are becoming more and more expensive and their benefit is decreasing because of a degrading soil resource base. Furthermore, the rise in production costs makes total reliance on inorganic fertilisers more uneconomical for most growers in the agricultural sector; making it imperative for researchers to come up with options which increase the efficient use of fertiliser, and also to identify other nutrient sources — such as legumes — that are not capital intensive. The velvet-bean technique is known to researchers and farmers worldwide for a considerable amount of time, but not in our country. As the technique becomes better known to South African farmers, it can be considered in a broader sense as a modern way to add nitrogen to the soil; benefitting, amongst others, the subsequent crop. The velvet-bean approach has a window of opportunity which can lead to higher yields in crop production, decline in labour costs, crop diversification, as well as agro-processing — all resulting in improved food security for South Africa. Adopting the velvet bean into a production system can benefit a farmer, by achieving maize yields of 3 t/ha–4 t/ha (similar to yields normally obtained with recommended levels of fertilisation at 130 kg N/ha) without applied nitrogen fertiliser or input for weeding. Velvet beans, as an intercrop, can provide more than 100 kg N/ha to the following crop. However, literature shows a declining trend over time for all systems, which suggests that additional external inputs (probably P and K fertiliser) are required to achieve full sustainability. The adoption of the velvet bean in the South African maize industry would result in import savings of about 158 million tons of urea or about R591 billion/year. Information presented in this mini-dissertation is considered to be the current state of knowledge on establishing, managing, and utilising the velvet bean as a legume in South Africa’s commodity market; with the belief that it will expand the use of the bean, and will enhance the benefits from its use. / MBA, North-West University, Potchefstroom Campus, 2015