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The seed storage fungi (xerotolerant) species of the genera Aspergillus and Penicillium} are renowned for their devastating effects on stored grain and grain products. In view of the fact that most of these fungi Iiberate toxins which can be harmful to both man and his livestock this problem is becoming increasingly relevant, particularly in developing countries. The seed storage fungi are said to be saprophytes and opportunistic invaders of dead or naturally dried organic matter, and as such no direct host-pathogen relationship has been ascribed to them. This dissertation reports aspects of an investigation into the modes/pathways utilised by these fungi in their infection of maize caryopses (seeds) and plants. The work involved studies on: the effects of protracted storage on maize seeds; the morphology of storage fungi; extra-cellular enzymes of storage fungi; the pathways utiIised by the storage fungi in invasion of seed tissues; and the effects of the storage fungi on the seeds. Correlations have been made on a species basis between the extent of seed deterioration and fungal aggressiveness. The results of these investigations indicated that apart from affecting seed vigour and viability, these fungi can also affect plant vigour. This latter aspect was further investigated to determine whether a seed storage fungus could infect germinating maize seeds, and remain an internal contaminant of the tissues during plant growth and development. These latter studies revealed that Aspergillus flavus var. columnaris is capable of systemic transmission from one seed generation to the next. This hitherto unrecognised phenomenon apart from indicating that the fungal species is in fact a biotroph as well as a saprophyte, also has implications In control measures. / Thesis (Ph.D.)-University of Natal, Durban, 1990.

Seeds of wild rice (Zizania palustris var. interior) have been reported to show highest survival when dehydrated at 25 QC. It has also been reported that axis cells sustained least damage at this drying temperature. In the present study, a linear relationship between drying rate and dehydration temperature was established. Whereas highest positive tetrazolium staining and lowest leakage were recorded for seeds that were dehydrated at 25 QC, maximum germination was recorded for seeds dried at 20 QC. A proportion of seeds showed the presence of glasses, irrespective of the dehydration temperatures used. Parameters of the glass to liquid transition, however, correlated with neither water content nor sugar profiles. The ratio of raffinose to sucrose was similar among all the treatments. A hydroperoxide test revealed a linear relationship between peroxide levels and temperature of drying although the levels of fatty acids were not correlated with hydroperoxide levels. Butanal levels and total aldehydes evolved, on the other hand, showed a high negative correlation with peroxide levels. Electron microscopy showed that the variability and relative abundance of peripheral membrane complexes (PMCs) was the highest for cells of embryonic axes dehydrated at 25 QC and the lowest for embryonic axes of seeds dried at 10 QC. Furthermore, intramembrane particles (IMPs) were evenly distributed in cells of axes dried at 25 or 37 QC. In contrast, membranes of cells of axes dehydrated at 10 QC showed large IMP-free areas. The relative abundance of IMPs was the highest for cells of embryonic axes dried at 25 QC, and the lowest for cells of axes dehydrated at 10 QC. From these observations, it is suggested that membrane phase transition, with the concomitant elimination of proteins, accompanies dehydration of Z. paluslris seeds at 10 QC, whereas at 37 QC peroxidation may predominate. / Thesis (M.Sc.)-University of Natal, Durban, 1996.

The International Seed Testing Association and the Association of Official Seed analysts define seed vigour as the ability of a seed lot to perform during the germination process and crop stand establishment under a wide range of environmental conditions. There are many ways to determine seed vigour, but few satisfy the requirements of being simple, inexpensive and reproducible, among others, to permit the seed industry to adopt seed vigour as an indicator of seed quality when they sell seeds. Hence, the standard germination test, which is performed under uniform and favourable conditions, is generally used to indicate seed quality when seeds are marketed. The objective of this study was to determine the performance of tomato and pepper seeds in response to pre-germination hydration and dehydration relative humidities (12%, 49% and 75% RH). Before hydration, seeds were hydrated at three temperatures (10°C, 20°C and 30°C). Hydration was performed by imbibing pre-weighed pepper ('Santarini' and 'California Wonder'), Chilli and tomato ('Heinz', 'Marondera' and 'Roma') seeds for 2 h in 10 ml of distilled H(2)0 per 100 seeds at 10°C, 20°C and 30°C. Dehydration was performed by change in seed mass determined during a 72-hour dehydration at 12%, 49% and 75% RH. Seed performance in response to imbibition and dehydration was determined by leakage of electrolytes from seeds during imbibition, laboratory germination capacity and seedling emergence under simulated shadehouse nursery conditions. A pot experiment was conducted to determine the effects of seed treatments on yield. Seed mass increased by about 50% during the 2-hour of hydration. Dehydration was hastened by decreasing the RH, and 12% RH significantly (P < 0.05) reduced the post-imbibition seed moisture content compared with 49% and 75% RH. The latter two relative humidities reduced the seed moisture content to about 10% and 15%, respectively, for all cultivars, irrespective of imbibition temperature. Low imbibition temperature (10°C) significantly (P < 0.01) increased electrolyte leakage, compared with high imbibition temperatures (20°C and 30°C), which were not significantly different from each other. At all hydration temperatures, low RH (12%) caused a significant (P < 0.01) decrease in seed germination whereas 49% RH and 75% RH apparently had a priming effect on seeds. There was no significant difference between imbibition temperatures, with respect to seed germination, but 100G caused a significant decrease in germination index, a measure of seed vigour. Seedling emergence was significantly (P < 0.01) reduced by both low imbibition temperature (10oG) and low dehydration relative humidity (12% RH). The negative effects of low imbibition temperature and rapid dehydration at 12% RH were also observed as stunted seedling growth. Principal component analysis and linear regression were used to determine a statistical model to predict seedling emergence from germination percentage. The model predicted emergence consistently, but it overestimated it by about 2% to 3%. It is concluded that low imbibition temperature and rapid dehydration can be used to simulate stress to determine seed performance in pepper and tomato. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2005.

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Dormancy characteristics and optimum conditions for germination of Cleome gynandra seeds have not been explained. Seed storage proteins were extracted, analysed with SDS-PAGE and sequenced. Seed proteins of Cleome were characterised by comparison with those of wild mustard (Brassica kaber). Wild mustard showed seed proteins composed of two α-chains of molecular weight (24-32 kDa) and another two β-chains of 18-22 kDa. The seed proteins of Cleome comprised two α-chain polypeptides of molecular weight (25-30 kDa), two β-chain polypeptides of molecular weight (18-20 kDa) and a smaller β-chain of 13-15 kDa. The storage proteins occurred in the seeds as dimeric complexes of molecular weight 40-65 kDa, which were broken into polypeptide chains of approximately 20 and 30 kDa by the reducing . action of DTT. Comparison with proteins in the proteome library and similarity index further confirmed that the seed proteins of Cleome had similarities with those of wild mustard. Two dimensional SDS-PAGE showed that the two species have nine similar polypeptides and four different ones. Events associated with dormancy release during seed germination still require explanation. Seeds of Cleome are characterised by low germination and there has been no explanation for this. Changes in protein expression during germination of Cleome in the presence or absence of light and at constant or alternating temperatures were examined. The germination of Cleome seeds at 20 degrees C was inhibited by light, but it was improved at 20 degrees C in darkness. There was no photoinhibition when seeds were germinated at constant 30 degrees C or alternating 20/30 degrees C (16 h night and 8 h day) for 10 days. Four proteins were observed to decrease in expression as germination progressed, but remained unchanged during photoinhibition. Photoinhibition was expressed more in seeds that were harvested late, after the pods had turned brown. These seeds showed a fifth, low molecular weight protein (13 kDa) that was absent from the immature seeds and embryos. Photinhibition is a pseudo-dormancy condition during which seed storage proteins are not utilised and the seed coat could partially play a role in it. The temperatures for the germination of Cleome in darkness have been determined. However, prior to this study the effects of temperature, light and pre-germination treatments (chilling, scarification, hydration and germination in the presence of KN0(3) or GA(3) on the germination of the seeds of this species have not been investigated. Seeds were germinated for 10 days and the final count of germination was used to determine seed performance. The highest germination percentage (60% and 80%, for a 2-year old and a l-year old seed lot, respectively) of untreated seeds was achieved when alternating temperatures of 20/30 degrees C (16 h/S h) in the dark or constant 30 degrees C in the dark were used. Among the pre-germination treatments, only scarification (puncturing of seeds at the radicle end) improved germination. Seeds were found to be negatively photoblastic, and the phenomenon was more pronounced when they were germinated at 20 degrees C and 12 h photoperiod or longer. Germination of photoinhibited seeds was, however, improved by treatment with GA(3) It is recommended that the germination of Cleome be undertaken under conditions of darkness and at either alternating 20/30 degrees C or continuous 30 degrees C. Seed lot vigour and seedling vigour are two important seed quality aspects that are used in defining the seed germination process. Seed germination is appropriately characterised by radicle protrusion and the attainment of normal seedling structures. However, the international rules for testing seeds combine radicle protrusion and normal seedling attainment in separating seed germination into the first and final counts. The challenge to a seed analyst testing the germination of a species whose first and final counts are unknown is that there is no statistical guideline to determine these important stages of seed germination. Cauliflower and broccoli, for which the first and final counts are published in the international rules for testing seeds and Cleome, for which there is no data on the first and final counts, were examined to determine the statistical significances of the first and final counts. Analysis of variance, logistic regression, 'broken-stick' regression models and survival analysis procedures were used. Analysis of variance showed that there were no differences between the germination percentages on the fourth, fifth and seventh days of germination. Low and stable standard deviations were recorded when evaluating germination after the fourth day. The germination curves of broccoli and cauliflower did not fit the Gompertz curve but fitted the exponential curve. The broken-stick model 'broke' the cumulative germination curve for the Cleome seed lots into two linear curves that were significantly different, but failed to break those for broccoli and cauliflower. However, this study confirmed the first and final counts for broccoli and cauliflower as determined by the international rules for testing seeds. Broken-stick modelling and life table analyses confirmed the fourth day as being appropriate to determine the first count for Cleome germination. There was no evidence of further seed germination after the seventh day as shown by probability density and hazard rate. It is suggested that for Cleome, the 'first count' and 'final count' be performed on the fourth and seventh day of the germination, respectively. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2005.

Orientador: Sandra Helena Unêda-Trevisoli / Coorientador: Antonio Orlando Di Mauro / Coorientador: Cibele Chalita Martins / Banca: Everton Luis Finoto / Banca: Ivana Marino Bárbaro Torneli / Banca: Rinaldo Cesar de Paula / Banca: Gustavo Vitti Môro / Resumo: O presente estudo foi realizado com os objetivos principais de: verificar as associações existentes entre caracteres agronômicos e caracteres relacionados à qualidade fisiológica de sementes de soja; determinar alterações fisiológicas e no teor de óleo em sementes de soja, ao longo do período de armazenamento, além de selecionar progênies superiores de soja por meio de análises multivariadas. Para isto, as relações existentes entre os caracteres agronômicos de plantas e fisiológicos de sementes foram verificadas por meio da análise de correlações canônicas em sete populações e duas cultivares comerciais, em três gerações: plantas F3 e sementes F4; plantas F4 e sementes F5; e sementes e plantas na geração F4. Os caracteres agronômicos de plantas (grupo I) avaliados foram: número de dias para maturidade, altura da planta na maturidade, altura de inserção da primeira vagem, número de vagens, produção de grãos e teor de óleo. A qualidade fisiológica das sementes (grupo II), foi avaliada por meio do teste de germinação, envelhecimento acelerado, emergência e índice de velocidade de emergência. As mesmas populações e cultivares também foram avaliadas antes do armazenamento e após seis meses, armazenadas em ambiente com temperatura e umidade controladas, através de testes de germinação, vigor, teor de água e teor de óleo, em esquema fatorial 2 x 9. Para as análises multivariadas, 20 populações segregantes de geração F4, foram avaliadas para os seguintes caracteres agronômicos: númer... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: This study aimed to examine the associations between agronomic traits and traits related to physiological seed quality in soybean seeds, determine physiological and oil content alterations during the storage and select superior progenies using multivariate analysis. For this, the relationships between agronomic traits and physiological of seed traits were evaluated using canonical correlation analysis in seven segregating populations and two commercial cultivars conducted in three generations: plants F3 and seeds F4, plants F4 and seeds F5 and seeds and plants in generation F4. The agronomic traits (group I) evaluated were: number of days to maturity, plant height at maturity, first pod height, number of pod per plant, grain yield and oil content. The seed physiological quality (group II) was evaluated by percentage of germination, percentage of emergence, emergence speed index and accelerated aging. The same populations and cultivars were also evaluated before the storage and after six months stored in cold room by germination test, vigor, seed moisture and oil content, arranged in a 2 x 9 factorial design. For the multivariate analysis, 20 segregating populations in generation F4 were evaluated using the following agronomic traits: number of days to flowering, number of days to maturity, plant height at maturity, first pod height, number of branches per plant, number of pod per plant, number of nodes per plant, grain yield and oil content. It was used the principal compone... (Complete abstract click electronic access below) / Doutor

O presente trabalho teve como objetivos verificar a eficiência de procedimentos para avaliação do potencial fisiológico de sementes de pimentão e procurar identificar suas relações com a germinação sob diferentes temperaturas e com a emergência de plântulas. Paralelamente, foram efetuadas análises de imagens obtidas com o emprego de radiações X, procurando associar a morfologia interna das sementes ao seu desempenho e determinar possíveis causas de variações do potencial fisiológico. Utilizaram-se cinco lotes de sementes dos híbridos Reinger e Sentinel. A avaliação do potencial fisiológico das sementes foi realizado mediante a condução do teste de germinação, envelhecimento acelerado com solução saturada de NaCl (48h/41°C), emergência de plântulas (percentagem e velocidade), teste de tetrazólio (3h/45°C para embebição e 2h/5°C para a coloração das sementes) e teste de germinação (percentagem e velocidade) sob cinco faixas de temperatura (15°C, 18°C, 21°C, 25°C e 30°C), em mesa termogradiente. Para o teste de raios X, as sementes radiografadas foram classificadas em função do estádio de desenvolvimento e morfologia dos embriões; posteriormente ao teste de germinação, procurou-se relacionar a estrutura das sementes com as respectivas plântulas/sementes resultantes. Os testes de envelhecimento acelerado com solução saturada de NaCl e de tetrazólio são adequados para a avaliação do potencial fisiológico das sementes e, lotes vigorosos apresentam bom desempenho sob variações de temperatura, na germinação. O teste de raios X é eficiente na identificação de danos e anormalidades no embrião associados à germinação de sementes de pimentão. / This study aimed to verify the efficiency of procedures for the physiological potential assessment of pepper seeds and seek to identify its relationship with germination under different temperatures and the emergence of seedlings. In parallel, we performed the analysis of images, obtained with the use of radiation X, seeking to associate the internal morphology of seeds to their performance and to determine possible causes of changes of physiological potential. The study used five seed lots of hybrids Reinger and Sentinel. The evaluation of physiological potential of the seeds was achieved by conducting the germination test, accelerated aging with saturated solution of NaCl (48h/41°C), emergence of seedlings (percentage and speed), the tetrazolium test (3h/45°C for imbibition and 2h/5°C for colouration of seeds) and germination test (percentage and speed) on five tracks of temperature (15°C, 18°C, 21°C, 25°C and 30°C) in thermogradient table. For the X-ray test, radiographed seeds were classified according to the stage of development and morphology of the embryos; after the germination test, the structure of seeds were associated with the respective resulting seedlings/seeds. The accelerated aging test with saturated solution of NaCl and tetrazolium test are appropriate for assessing the physiological potential of pepper seeds, and vigorous lots show good performance under variations of temperature in germination. The X-ray test is effective in identifying damage and abnormalities in the embryo associated with germination of pepper seeds.

O presente trabalho teve como objetivos verificar a eficiência de procedimentos para avaliação do potencial fisiológico de sementes de pimentão e procurar identificar suas relações com a germinação sob diferentes temperaturas e com a emergência de plântulas. Paralelamente, foram efetuadas análises de imagens obtidas com o emprego de radiações X, procurando associar a morfologia interna das sementes ao seu desempenho e determinar possíveis causas de variações do potencial fisiológico. Utilizaram-se cinco lotes de sementes dos híbridos Reinger e Sentinel. A avaliação do potencial fisiológico das sementes foi realizado mediante a condução do teste de germinação, envelhecimento acelerado com solução saturada de NaCl (48h/41°C), emergência de plântulas (percentagem e velocidade), teste de tetrazólio (3h/45°C para embebição e 2h/5°C para a coloração das sementes) e teste de germinação (percentagem e velocidade) sob cinco faixas de temperatura (15°C, 18°C, 21°C, 25°C e 30°C), em mesa termogradiente. Para o teste de raios X, as sementes radiografadas foram classificadas em função do estádio de desenvolvimento e morfologia dos embriões; posteriormente ao teste de germinação, procurou-se relacionar a estrutura das sementes com as respectivas plântulas/sementes resultantes. Os testes de envelhecimento acelerado com solução saturada de NaCl e de tetrazólio são adequados para a avaliação do potencial fisiológico das sementes e, lotes vigorosos apresentam bom desempenho sob variações de temperatura, na germinação. O teste de raios X é eficiente na identificação de danos e anormalidades no embrião associados à germinação de sementes de pimentão. / This study aimed to verify the efficiency of procedures for the physiological potential assessment of pepper seeds and seek to identify its relationship with germination under different temperatures and the emergence of seedlings. In parallel, we performed the analysis of images, obtained with the use of radiation X, seeking to associate the internal morphology of seeds to their performance and to determine possible causes of changes of physiological potential. The study used five seed lots of hybrids Reinger and Sentinel. The evaluation of physiological potential of the seeds was achieved by conducting the germination test, accelerated aging with saturated solution of NaCl (48h/41°C), emergence of seedlings (percentage and speed), the tetrazolium test (3h/45°C for imbibition and 2h/5°C for colouration of seeds) and germination test (percentage and speed) on five tracks of temperature (15°C, 18°C, 21°C, 25°C and 30°C) in thermogradient table. For the X-ray test, radiographed seeds were classified according to the stage of development and morphology of the embryos; after the germination test, the structure of seeds were associated with the respective resulting seedlings/seeds. The accelerated aging test with saturated solution of NaCl and tetrazolium test are appropriate for assessing the physiological potential of pepper seeds, and vigorous lots show good performance under variations of temperature in germination. The X-ray test is effective in identifying damage and abnormalities in the embryo associated with germination of pepper seeds.