No description available.

The xerophytic gourds, Apodanthera undulata and Cucurbita digitata, hold promise as new sources of starch for industrial and domestic use as world population increases and food demands become greater. Thus, understanding of the chemical and physical properties of the starches from these arid land plants is required. Moisture content, ash, fiber and starch content of A. undulata and C. digitata roots were comparable to Solanum tuberosum (potato) and Manihot utilissima (tapioca). High lipid content was observed in A. undulata, but C. digitata was similar to tapioca in this respect. The composition of subject starches was comparable to standard starches. The lipid content of C. digitata starch was similar to that of corn starch, but A. undulata starch exhibited a higher content. A. undulata starch showed a higher iodine binding capacity, hence a higher amylose content, than C. digitata, potato and C. foetidissima starches. The number of terminal aldehyde groups and the average granule size of subject starches were comparable to tapioca starch. Interestingly, gelatinization temperature and percent sag test values were more similar to cereal starches such as corn, than to potato or tapioca. The swelling power of both starches was intermediate between corn and tapioca, while the solubility of A. undulata was similar to corn starch. The paste viscosity of A. undulata and C. digitata, when compared to corn, potato and C. foetidissima, proved to be most similar to corn. Viscosity maxima were intermediate between corn and potato. C. digitata starch was very stable, showing little change in paste viscosity after heating for one hour at 90°C. Increases in viscosity occurred during the cooling period for A. undulata, C. digitata and corn, but negligible changes occurred in C. foetidissima and potato. Starches isolated from A. undulata, C. digitata and potato were evaluated nutritionally by an in vivo study. Increases in digestibility of autoclaved starches (85% for A. undulata, 85% for C. digitata and 91% for potato) over raw starches (40% for A. undulata, 40% for C. digitata and 24% for potato) were confirmed by statistical analysis. Feed consumption and body weight gain were higher than for the potato starch diet. Autoclaving also improved net protein ratio and protein efficiency ratio. The fine structure of the macromolecular fractions amylose and amylopectin from starches of A. undulata and C. digitata were examined. The dimethyl sulfoxide method proved to be effective for fractionation of each starch. Purity of these components was confirmed by iodine binding capacity, and they were found to be similar to standard starches. Calculated values for degree of polymerization (DP) were similar to that of potato. Study of the fine structure of these components showed beta-amylolysis limits of approximately 90% for the amyloses and above 60% for the amylopectins. These values were similar to those of potato and intermediate between tapioca and cereal starches. The average chain length of the A. undulata amylopectin was found to be 25 with an outer chain length of 18 and an inner chain length of 6. The average chain length of 18 and an inner chain length of 6. The average chain length for C. digitata amylopectin was 26 with an outer chain length of 19 and an inner chain length of 6. These relatively long exterior layers with respect to the short interior layers show the amylopectins of these starches to be asymmetric molecules comparable to potato.

Thesis (Ph.D. Agriculture (Soil Science)) -- University of Limpopo, 2017. / Climate change and variability pose a significant challenge to future global food security due to changes in mean climatic conditions which are rendering many areas marginally suitable for crop production. Erratic rains, drought, heat stress and declining soil fertility are some of the factors limiting crop productivity in many arid and semi-arid areas. Furthermore, water resources that could be used to mitigate drought and erratic rains, are also threatened by both scarcity and overuse. To ensure food security in the future, adaptation strategies at crop and management levels should be explored. Adaptation to future drier and warmer climates calls, among others, for improvement in drought resistance of crops through measures such as screening traits for drought tolerance and water use efficiency. This PhD study was carried out at University of Limpopo experimental farm, Limpopo Province, South Africa, a region with a semi-arid climate and mean annual rainfall of ca. 500 mm. The main aim of the study was to evaluate the use of plant δ13C and δ18O as screening traits for potential yield and water use efficiency of crop genotypes under drought conditions. The study also determined the agronomic performance of cowpea (Vigna unguiculata L. Walp.) and triticale (x. Triticosecale Wittmack) genotypes under varying soil moisture conditions including biological nitrogen fixation for cowpea. Both crops were grown under field conditions and the following four moisture levels (averages per level) were applied: well-watered (ca. 420 mm), moderately well-watered (ca. 350 mm), medium stress (ca. 290 mm), and severe stress (ca. 220 mm). The triticale experiment evaluated the agronomic performance and the spectral response of triticale to water stress under semi-arid conditions. The results showed a significant (P < 0.05) influence of moisture levels on the spectral reflectance, as well as on biomass and grain yield performance of triticale. However, these measured parameters did not significantly (P > 0.05) respond to genotypes probably due to the pre-screening of the genotypes or the lack of distinct genetic diversity in the studied parameters. Under well-watered conditions, triticale produced a grain yield of 3.9 t ha-1 in 2013 and 4.9 t ha-1 in 2014. These yields were however, found to be low when compared to other studies. Even though, no statistical differences were observed among the genotypes, Agbeacon showed a tendency of higher performance compared to the other genotypes. Of the four spectral indices tested, water based indices i.e. the water index (WI) and normalised difference water index (NDWI) were found to be more effective in detecting leaf water status compared to greenness based indices (normalised difference vegetation index and nitrogen reflectance index). This is because NDWI and WI respond to short term changes in water content of leaves. Overall, the performance of triticale showed a good adaptation to semi-arid conditions. The evaluation of δ13C and δ18O as screening traits for potential yield and water use efficiency under drought conditions produced interesting results. The findings showed that, Δ13C was positive and strongly related to grain yield and thus has potential to be used as a surrogate for grain yield in triticale under water stress. We also found a negative relationship between Δ13C and intrinsic water use efficiency (WUEintrinsic), which suggests that breeding for higher WUEintrinsic in triticale may not necessarily yield the desired improved grain yield. Measured grain Δ13C and flag leaf Δ13C suggested minimum contribution of pre-anthesis assimilates to grain filling under water stress, contrary to what is reported in literature. However, for concrete conclusions on the source of assimilates to the grains under drought conditions, further studies are still needed. Combining δ13C and δ18O provided more information on the physiological responses of triticale to varying moisture levels. The δ13C and δ18O were used to test the dual isotope model by Scheidegger et al 2000 and the results showed that, vapour pressure deficit (VPD) of air plays an important role in the operation of the model. The study indicated that the model worked only under high VPD when stomatal conductance limits transpiration rate but failed to work when VPD was relatively low and limiting transpiration rate. In order to address the declining soil fertility in the smallholder farming sector as well as the predicted loss in productivity of the commonly grown dry bean, this PhD study evaluated cowpea genotypes for biomass yield, grain yield and biological nitrogen fixation (BNF) under varying moisture levels. The results showed that soil moisture levels indeed affect biomass production, grain yield, nodule formation and the ability of cowpea to fix atmospheric nitrogen. BNF and nodule formation were the most sensitive to water stress compared to the other parameters. Severe water stress reduced BNF by 57% relative to well-watered conditions while nodule mass was reduced by 80% for the same soil moisture levels. Genotype TV4607 was superior in most of the parameters determined except for grain yield. As a result, TV4607 produced the highest biomass and returned the most nitrogen back to the soil compared to the other genotypes. However, IT00K-1263 emerged as the superior genotype due to its ability to produce the optimum balance of biomass, grain yield and BNF. Stomatal behaviour of cowpea under varying moisture levels was also investigated and the results showed sensitivity of stomatal conductance to soil moisture levels. As expected, stomatal conductance was high under well-watered conditions compared to water stressed conditions. Genotypic variation in stomatal conductance was only observed at early stages of cowpea growth i.e. at 47 and 54 days after planting (DAP). In conclusion, this PhD has shown that δ13C has potential to be used in breeding for drought resistance in triticale and probably other small grain crops. This study also revealed that there is minimum contribution of pre-anthesis assimilates to grain filling under water stress, contrary to what is reported in literature and hence more research is needed.The evaluated genotypes of triticale and cowpea showed tolerance to drought stress under semi-arid conditions. Agbeacon for triticale and IT00K-1263 for cowpea were identified as the most promising genotypes and hence their adoption in the smallholder farming system could be a step towards adapting to future warmer and drier climates

No description available.

Submitted by Fabio Sobreira Campos da Costa (fabio.sobreira@ufpe.br) on 2017-02-21T14:28:20Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) SILVIA_ROBERTA_SANTOS.pdf: 1500355 bytes, checksum: 1e02b5fad9ccef21b9e9af2f593d567c (MD5) / Made available in DSpace on 2017-02-21T14:28:20Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) SILVIA_ROBERTA_SANTOS.pdf: 1500355 bytes, checksum: 1e02b5fad9ccef21b9e9af2f593d567c (MD5) Previous issue date: 2016-02-29 / CAPES / Espécies vegetais que ocorrem na Caatinga estão submetidas ao clima semiárido que se caracteriza por altas temperaturas, baixa precipitação e elevadas taxas de transpiração, que favoreceram o desenvolvimento de adaptações morfoanatômicas, ecológicas e fisiológicas. Esse ambiente xérico abriga inúmeras plantas conhecidas como xerófitas, cujos caracteres xeromórficos estão envolvidos principalmente com o estresse hídrico. Na maioria das vezes, o estrato herbáceo, considerado efêmero, é negligenciado quanto à sua investigação em detrimento das espécies que se mantém na paisagem, como as arbustivas e arbóreas, tendo sua biologia pouco explorada e consequentemente pouco compreendida quanto às estratégias de sobrevivência em ambientes xéricos como a caatinga. Assim, esse trabalho objetivou caracterizar morfoanatomicamente espécies de herbáceas identificando caracteres adaptativos típicos e como estes podem ser influenciados pela dificuldade de obtenção de água motivada pela distância do curso de água em três áreas classificadas em: AA-curso de água ausente, AT-curso de água temporário, AP-curso de água permanente. As espécies estudadas apresentaram características xeromórficas típicas, as quais conferem vantagem adaptativa em ambientes semiáridos, tais como a presença de: cutícula espessa, parênquima paliçádico com várias camadas incluindo mesofilo isobilateral, um indumento denso marcado pela presença de muitos tricomas, cristais de oxalato de cálcio, aumento da região cortical radicular, variações na atividade cambial e densidade de elementos de vaso e fibras xilemáticas. O índice de plasticidade fenotípica apresentou maiores valores para as espécies perenes indicando ajustamento às condições ambientais. Entretanto, os caracteres xeromórficos sofrem poucas alterações significativas nas diferentes áreas estudadas, porém, esses parâmetros foram relevantes para compreender o comportamento das herbáceas no ambiente e podem servir de base para novos estudos envolvendo herbáceas e xerófitas de modo geral. No mais, aspectos como variações cambiais associados à ultraestrutura de organelas e parede celular de tecidos distintos, pode ser a chave para a compreensão de respostas à disponibilidade hídrica nas áreas aqui estudadas. / Plant species that occur in the Caatinga are subject to the semiarid climate characterized by high temperatures, low rainfall and high transpiration rates, which favored the development of morphoanatomic, ecological and physiological adaptations. This xeric environment covers numerous plants known as xerophytes, whose xeromorphic characters are mainly involved with water stress. In most cases, the herbaceous stratum, considered ephemeral, is neglected as its research to the detriment of species that remains in the landscape, such as shrub and tree, with its unspoilt biology and therefore little understood about the survival strategies in environments xeric such as Caatinga. So, This study aimed to feature morphological and anatomically herbaceous species identifying typical adaptive characters and how these can be influenced by the difficulty of obtaining water driven by the distance of the watercourse in three areas classified as: AA – no water course, AT- temporary water course and AP-permanent water course. The species present typical xeromorphic characteristics which confer adaptive advantage in semi-arid environments, such as the presence of: a thick cuticle, palisade parenchyma with multiple layers including isobilateral mesophyll, a dense indumentum marked by the presence of many trichomes, calcium oxalate crystals, increased root cortical region, variations in foreign exchange activity and density of vessel elements and xylem fiber. The phenotypic plasticity index shows higher values for perennial species indicating adjustment to environmental conditions. However, xeromorphic characters suffer few significant changes in the different areas studied, however, these parameters are relevant to understanding the behavior of herbaceous on the environment and provide the basis for new studies involving herbaceous and in general xerophytes. Therefore, aspects such as currency fluctuations associated with ultra organelles structure and cell wall distinct tissues, may hold the key to understanding responses to water availability in the areas studied here.

Submitted by Rosangela Silva (rosangela.silva3@unioeste.br) on 2018-07-06T12:01:53Z No. of bitstreams: 2 Aline Viana.pdf: 2056531 bytes, checksum: 5edb7c5297a393f052e5b8bc319a1bcf (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2018-07-06T12:01:53Z (GMT). No. of bitstreams: 2 Aline Viana.pdf: 2056531 bytes, checksum: 5edb7c5297a393f052e5b8bc319a1bcf (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2018-02-06 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / (Morphology and foliar anatomy of angiosperm species occurring in the sand fields of the Pampa biome). Part of the vegetation in the southwest of Rio Grande do Sul (RS) is classified as sand fields, phytophysiognomy of the Pampa with sandy soils, susceptible to the natural process of sandstone, intensified by anthropic action. This process has contributed to a reduction in the biological diversity of the biome and is even more worrisome for species with restricted occurrence and/or the threat of extinction. The objective of this work was to characterize the leaf blade morphoanatomy of 20 angiosperm species of the sand fields, of which 8 are considered endangered, seeking to identify strategies that allow adaptation to the rural environment. To this end, individuals from different populations of each species were collected in sand-field regions of the Pampa biome. Leaf blades in frontal view were analyzed using scanning electron microscopy (SEM), light microscopy (LM), and transverse sections (TS) in LM. Microchemical tests were also performed in TS observed in LM. It was observed that, although they belong to distinct phylogenetic groups, many of the studied species share characteristics which can be interpreted as adaptive strategies, such as trichomes covering the entire leaf surface, stomata on both sides, compact mesophyll, druses, secretory channels, phenolic compounds, and mucilage. We conclude that these species, occurring in sand-field regions, have characteristics that confer adaptation to dry environments and/or water deficits. In this way, we emphasize the importance of the creation of conservation units in the sand-field region, aiming to preserve these species. / (Morfologia e anatomia foliar de espécies de angiospermas com ocorrência nos campos de areais do bioma pampa). Parte da vegetação do sudoeste do Rio Grande do Sul (RS) é classificada como campos de areais, fitofisionomia do Pampa que ocorre sobre solos arenosos, suscetíveis ao processo natural de arenização, intensificado pela ação antrópica. Esse processo tem contribuído para a redução da biodiversidade do bioma, sendo ainda mais preocupante para espécies com ocorrência restrita e/ou ameaçadas de extinção. Nesse contexto, esse trabalho teve como objetivo caracterizar a morfoanatomia da lâmina foliar de 20 espécies de angiospermas dos campos de areais do RS, das quais oito são consideradas ameaçadas de extinção, buscando identificar estratégias adaptativas ao ambiente campestre. Para isso, indivíduos de diferentes populações de cada espécie foram coletados nos municípios de Alegrete, Manoel Viana e São Francisco de Assis, RS. Lâminas foliares em vista frontal foram analisadas com microscópio eletrônico de varredura (MEV) e microscopia de luz (ML) e em secção transversal (ST) em ML, e testes microquímicos das ST. Foi possível observar que, apesar de pertencerem a grupos filogenéticos distintos, muitas das espécies estudadas compartilham características, que podem ser interpretadas como estratégias adaptativas, destacando-se: tricomas tectores cobrindo toda a superfície foliar, estômatos em ambas as faces, mesofilo compacto, drusas, canais secretores, compostos fenólicos e mucilagem. Concluímos que essas espécies com ocorrência aos campos de areais possuem características adaptativas ao ambiente seco e/ou para déficits de água. Dessa forma, ressaltamos a importância da criação de unidades de conservação na região dos campos arenosos, visando à preservação dessas espécies.