Dissertations / Theses on the topic 'Post-harvest physiology'

Experiments were carried out to identify the environmental factors influencing survival during emersion with the aim of suggesting modifications to present transit conditions in order to minimise physiological stress, thus improving scallop condition and survival. Results showed that increasing the emersion temperature from 5 to 20oC caused a reduction in maximum survival time of 62%. Similarly, reduction in relative humidity, from 95 to 70% saturation, resulted in 27% reduction in maximum survival time. Scallops exposed to a fine sea-water mist showed a 13% improvement in survival and the survival of scallops tested in December was 67% better than those tested in July. This seasonal effect appeared to be correlated with tissue glycogen concentrations which decreased by 29% over the same period. Maximum survival of any emersed scallop was 166 hours, although the animals were not in an edible condition after this time. Experimental factors which were found not to influence survival directly were packing orientation, enforced shell-valve closure and hypertoxic conditions (˜100% oxygen). These results implicated aspects of energy metabolism as the primary causes of scallop death during emersion and therefore this area was investigated in more detail. Further work showed that, heart rate had a positive linear relationship with temperature until ˜19oC. Thereafter, heart rate became irregular and uncoordinated, suggesting that poorer survival at high temperature is caused by loss of physiological integration and difficulty in meeting increased metabolic demands. The oxygen consumption rate of Pecten maximus in air is reduced to only 50% of the aquatic rate within 8 hours of emersion. This decline in respiration rate continued and was typically between 25 and 30% of the aquatic oxygen consumption rate after 60 hours in air. In addition, heart rate, haemolymph PO2, haemolymph pH and mantle cavity fluid PO2 and pH all decreased during emersion, implying that respiratory and circulatory systems were deteriorating.

The aim of this project was to down-regulate ACC oxidase (ACO) 1 and 2 and ACC synthase (ACS) in broccoli (Brassica oleracea var. italica) to lengthen post-harvest shelf-life. The ACO 1 and 2 and ACS cDNAs of broccoli were ligated into pSCV1.0 in sense and antisense orientations in relation to a CaMV 35S promoter and nos terminator. They were electroporated into the Agrobacterium rhizogenes co-integrate strain LBA 9402 pRi1855::GFP, and used to co-transform GDDH33, a doubled haploid line derived from the calabrese cultivar Green Duke. 150 transgenic hairy roots were identified by GFP fluorescence, and 18 were regenerated into whole plants. Four of these lines showed severe rol phenotype, which did not appear to be related to TL₋ DNA insert copy number. The floral buds from T₀ broccoli heads were assayed for post-harvest production of ethylene and chlorophyll levels. T₀ lines with ACC oxidase 1 and 2 constructs produced significantly less ethylene than the control plants, and chlorophyll loss was significantly reduced. A positive correlation between post-harvest bud ethylene production and chlorophyll loss was described by the equation y= 0.2386x-23.041. There were two copies of aco1 and aco2 in the Brassica oleracea genome of which one was mapped for each to linkage group 1 and 8, respectively.

Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico
O presente trabalho objetivou caracterizar as alteraÃÃes fÃsicas nos frutos e fÃsico-quÃmicas, enzimÃticas e sensoriais na Ãgua de coco de seis cultivares de coqueiro anÃo em sete estÃdios de desenvolvimento. As cultivares analisadas foram: AnÃo Verde de Jequi (AVeJ), AnÃo Amarelo de Gramame (AAG), AnÃo Amarelo da MalÃsia (AAM), AnÃo Vermelho de CamarÃes (AVC), AnÃo Vermelho da MalÃsia (AVM), sendo os frutos colhidos em um campo experimental da Embrapa Meio Norte (ParnaÃba, PI) nos seguintes estÃdios de desenvolvimento: 126, 147, 168, 189, 210, 231, 252 dias apÃs a abertura da inflorescÃncia. Logo apÃs a colheita, os frutos foram conduzidos para o laboratÃrio de Fisiologia e Tecnologia de PÃs-colheita na Embrapa AgroindÃstria Tropical, em Fortaleza, CearÃ, onde foram feitas as anÃlises fÃsicas e fÃsico-quÃmicas. Parte das amostras foram armazenadas a -85ÂC e, em seguida, transportadas para o LaboratÃrio de Fisiologia Vegetal, do Departamento de BioquÃmica e Biologia Molecular da Universidade Federal do CearÃ, onde foram feitas as anÃlises enzimÃticas. O experimento seguiu um delineamento inteiramente casualizado, em esquema fatorial do tipo 6 x 7,. Foram feitas as caracterizaÃÃes fÃsicas individuais dos frutos (massa, comprimento maior, diÃmetro, volume da Ãgua e cor da casca), e em seguida, as avaliaÃÃes fÃsico-quÃmicas da Ãgua de coco: sÃlidos solÃveis totais (SS), aÃÃcares solÃveis totais (AST) e redutores (AR), acidez total titulÃvel (ATT), relaÃÃo SS/ATT, pH, turbidez e proteÃna). Foram, tambÃm, avaliadas as atividades das enzimas que oxidam fenÃis [polifenoloxidase (PFO) e peroxidase especÃfica para o guaiacol (G-POD)], bem como aquelas do ciclo do ascorbato-glutationa [dismutase do superÃxido (SOD), catalase (CAT) e peroxidase do ascorbato (APX)], sendo tambÃm determinados alguns atributos sensoriais da Ãgua de coco. Os resultados deste experimento mostraram que as cultivares AVM, AAG e AAM, podem ser exploradas comercialmente, devido Ãs qualidade fÃsicas e fÃsico-quÃmicas que apresentaram. Pode-se concluir tambÃm que, independente da cultivar, o melhor perÃodo para colheita encontra-se na faixa de 189 a 210 dias de desenvolvimento dos frutos, pois nesse perÃodo as cultivares analisadas apresentaram os melhores atributos de qualidade.. NÃo foi detectada atividade da G-POD na Ãgua de coco de nenhuma das cultivares. A atividade da SOD na Ãgua de coco aumentou nos estÃdios iniciais de desenvolvimento dos frutos de todas as cultivares, destacando-se as cultivares AVG e AVeJ como as que apresentaram maiores atividades dessa enzima. A CAT mostrou-se a principal enzima eliminadora de perÃxido de hidrogÃnio da Ãgua de coco e sua atividade variou muito com o desenvolvimento dos frutos e tambÃm entre as cultivares
This study aimed at characterizing in fruit and physico-chemical, and sensory enzyme in the coconut water the of six dwarf coconut cultivars at seven stages of development. The studied cultivars were: Green dwarf from Jequi (GDJ), yellow dwarf from Gramame (YDG), yellow dwarf from Malaysia (YDM), Red dwarf from Cameroon (YDC), Red dwarf from Malaysia (RDM), Red dwarf from Gramame (RDG). Fruits were harvested from an experimental field, Embrapa Meio Norte (Parnaiba city, Piauà State), at the following stages of development: 126, 147, 168, 189, 210, 231, and 252 days after the opening of the inflorescences. Upon harvest, fruits were taken to the Laboratory of Postharvest physiology and technology at Embrapa Agroindustria Tropical, located in Fortaleza, CearÃ, were the physical and physic-chemical analyses were performed. Part of the samples were stored at -85ÂC and then transported to the Laboratory of Plant Physiology, Biochemistry and Molecular Biology Department from The Federal University of CearÃ, were the enzymatic study was conducted. The experimental designed was a completely randomized one in a factorial scheme 6 x 7. First physical characterization (mass, length, diameter, water volume, and color of the shell) was individually performed for each fruit, then the physic-chemical analyses of coconut water: total soluble solids (TSS), total soluble sugar (TSSu), reducing sugars (RS), total titratable acidity (TTA), sugar to acid ratio (TSS/TTA), pH, turbidity, and protein. It was also evaluated the activities of enzymes that oxide phenols [polyphenoloxidase (PFO) and peroxidase specific for the guaiacol (G-POD)], as well as those of the cycle of ascorbate-glutathione [superoxide dismutase (SOD), catalase (CAT) and the ascorbate peroxidase (APX). Moreover some of the sensory aspects of the water were evaluated. The results showed that the YDR, YDG, and RDG may be commercially exploited, due to their physical and physic-chemical characteristics. It was also concluded that, the best time for harvesting is somewhat between 189 to 210 days after fruit developed set, since right at this time the studied cultivars presented the best quality attributes. There was detected activity of G-POD in the coconut water from any of the cultivars. The activity of SOD in the coconut water increased in the early stages of development of the fruits of all the cultivars, such as RDG and YDG cultivars such as those that showed higher enzyme activity. A CAT proved to be the main enzyme eliminating of hydrogen peroxide of coconut water and its activity varied greatly it the development of the fruit and also between the cultivars

Com o objetivo de estudar a eficiência de herbicidas dessecantes, o momento ideal de aplicação, a viabilidade da antecipação da colheita e seus efeitos sobre o rendimento e as qualidades fisiológica e sanitária de sementes de feijão, foi instalada uma pesquisa em Área Experimental e no Laboratório de Análise de Sementes do Departamento de Produção Vegetal da Escola Superior de Agricultura "Luiz de Queiroz" em Piracicaba - SP. Para tanto, utilizou-se o cultivar Pérola, o qual foi semeado na safra da "seca", na população aproximada de 200.000 plantas/ha. O delineamento experimental foi o de blocos casualizados com quatro repetições em esquema fatorial 5 x 5, sendo cinco herbicidas, combinados com as cinco épocas de aplicação (28, 32, 36, 40 e 44 dias após o florescimento) e uma testemunha (sem aplicação de herbicida dessecante). A análise dos dados e a interpretação dos resultados obtidos permitiram as seguintes conclusões: os herbicidas dessecantes Paraquat e Paraquat associado a Diuron proporcionaram antecipação da colheita em onze dias, sem causar danos ao rendimento e a qualidade das sementes, enquanto para Glifosate e Glifosate + uréia a antecipação foi de seis dias; os herbicidas dessecantes Paraquat e Paraquat associado a Diuron não afetaram nem o rendimento, nem a qualidade das sementes produzidas, independemente da época de aplicação; os herbicidas Glifosate e Glifosate mais uréia somente quando aplicados aos 44 dias após florescimento não afetaram a qualidade das sementes e o herbicida dessecante Glufosinato de Amônio, independentemente da época de aplicação, afetou negativamente a qualidade das sementes produzidas.
Viewing to study the efficiency of desiccant herbicides, the ideal moment for their application, the feasibility of anticipating the harvest and their effects on yield and the physiological and sanitary quality of common bean seeds, an experiment was conducted at the College of Agriculture "Luiz de Queiroz", in Piracicaba, state of São Paulo, Brazil. Seeds of the cultivar 'Pérola' were sown during the dry season so as to result in a population of 200,000 plants/hectare. The experimental design was a randomized complete block with four replications in a 5 X 5 factorial arrangement - 5 herbicides in combination with 5 moments of application (28, 32, 36, 40, and 44 days after flowering) and a control treatment (no desiccant was applied). The statistical analyses of the data and the interpretation of the results allowed the following conclusions: Paraquat and Paraquat plus Diuron permited an 11 days anticipation in the harvest with no harm to seed quality or reduction in yield. For Glyphosate and Glyphosate plus Urea the anticipation was of 6 days. Paraquat and Paraquat plus Diuron were not harmful to seed quality or caused yield reduction in none of the moments of application. Glyphosate and Glyphosate plus Urea were not harmful only when applied 44 days after flowering. Ammonium Gluphosinate was always harmful to seed quality independently on the moment of application.

A uvaia (Eugenia pyriformis Cambess) é uma espécie nativa do Brasil, pertencente à família das mirtáceas, que se destaca por possuir um fruto de sabor e aroma agradável. No entanto, ainda faltam informações básicas, principalmente em relação a variabilidade existente em populações e sobre a fisiologia pós-colheita. Nesse contexto, este estudo objetivou caracterizar 31 acessos de uvaia originados de semente, quanto aos aspectos físicos, químicos e compostos bioativos e avaliar a influência do estádio de maturação na qualidade pós-colheita. O estudo foi dividido em duas etapas. Na primeira, caracterizou-se a variabilidade dos acessos baseado nos atributos físicos e químicos. Foram realizadas análises de massa fresca, massa de sementes, diâmetro, formato, cor da casca, rendimento de polpa, sólidos solúveis, acidez total titulável, ácido ascórbico, compostos fenólicos, carotenoides, flavonoides e capacidade antioxidante. Na segunda, avaliou-se a qualidade pós-colheita de uvaias colhidas em três estádios de amadurecimento quanto a cor da casca, sólidos solúveis, acidez titulável, ácido ascórbico, flavonoides, carotenoides, compostos fenólicos, capacidade antioxidante e compostos voláteis, respiração (CO2) e produção de etileno (C2H4). Entre os acessos foi verificada ampla diversidade na coloração dos acessos, variando de amarelo claro a alaranjado, com frutos classificados majoritariamente como achatados. Os atributos que apresentaram maior variação entre os acessos foram os sólidos solúveis, ácido ascórbico, compostos fenólicos e a capacidade antioxidante. Os resultados do armazenamento, mostraram que os frutos verdes alcançaram a mesma cor da casca, teor de acidez titulável, ácido ascórbico, flavonoides, carotenoides, compostos fenólicos e atividade antioxidante dos frutos maduros. Por outro lado, frutos colhidos verdes apresentaram baixo teor de sólidos solúveis e menor variedade de compostos voláteis. Não foi identificada relação entre o estádio de amadurecimento e a respiração. A produção de etileno foi diretamente proporcional ao estádio de amadurecimento. Estas informações sobre a qualidade da fruta colhida em diferentes estádios podem auxiliar a escolha daquele que melhor atender as exigências de uso para o consumo in natura e para a elaboração de produtos.
The uvaia (Eugenia pyriformis Cambess) is a native species of Brazil, belonging to the family Myrtaceae, which stands out for having a fruit of pleasant taste and aroma. However, basic information is still lacking, especially in relation to the variability in populations and their postharvest physiology. In this context, this study aimed to characterized 31 accessions of uvaia (propagated by seeds), as to physical, chemical and bioactive compounds and to evaluate the maturity stage influence on postharvest quality. The study was divided in two parts. First, was characterized the variability of the accessions based on physical and chemical attributes, were analyzed: fresh mass, seed mass, diameter, shape, skin color, yield of pulp, soluble solids, total titratable acidity, ascorbic acid, phenolic compounds, carotenoids, flavonoids and antioxidant capacity. Second, was evaluated the postharvest quality of uvaia at three stages of maturation as to skin color, soluble solids, titratable acidity, ascorbic acid, flavonoids, carotenoids, phenolic compounds, antioxidant capacity and volatile compounds, respiration (CO2) and production of ethylene (C2H4). There was a wide diversity in the color of the accessions, varied from light yellow to orange, with fruits classified mainly as flattened. The highest variation among the accessions was observed in the attributes of soluble solids, ascorbic acid, phenolic compounds and antioxidant capacity. During storage, the fruits picked green achieved the same color of the skin, titratable acidity, ascorbic acid, flavonoids, carotenoids phenolic compounds and antioxidant activity of mature fruits. On the other hand, fruits harvested green exhibited low content of soluble solids and less variety of volatile compounds. There was no relationship between respiratory rate and ripening. Ethylene production was proportional to the ripening stage. This information on the quality of the fruit harvested in different stages can help to choose the one that best meets the requirements of use for fresh consumption and for the elaboration of products.

A goiaba é uma fruta altamente perecível, e o conhecimento de sua fisiologia pós-colheita é fundamental para o emprego adequado de tecnologias, visando aumentar o período de conservação. O presente trabalho foi realizado com os objetivos de determinar índices de maturação; verificar a influência dos estádios de maturação na qualidade pós-colheita e determinar o padrão respiratório para goiabas ‘Kumagai’ e ‘Paluma’. Primeiramente determinaram-se os índices de maturação e a influência de cinco estádios de maturação na qualidade pós-colheita dos frutos. Os frutos foram selecionados em cinco estádios de maturação segundo a cor da casca: Estádio 1: cor da casca verde-escura; Estádio 2: quebra da cor verde; Estádio 3: início da coloração amarela da casca; Estádio 4: cor da casca parcialmente amarela; Estádio 5: frutos com cor da casca totalmente amarela, em seguida, foram armazenados em câmara a 25 + 2ºC e 80-90% UR e avaliados quanto às mudanças físico-químicas e qualidade sensorial. Posteriormente determinou-se o padrão respiratório dos frutos, analisando-se a atividade respiratória, a produção de etileno e as mudanças físico-químicas após a colheita para os estádios 1, 2 e 3. A cor da casca e a firmeza foram consideradas os melhores índices de maturação para ambas as variedades. A variedade Paluma também apresentou o ratio como um bom índice de maturação. As variáveis físico-químicas apresentaram pouca variação entre os estádios de maturação após o amadurecimento, porém foram observadas diferenças significativas em relação à análise sensorial, sendo as melhores notas atribuídas aos estádios 4 e 5 na variedade Kumagai e para o estádio 5 na variedade Paluma. O ponto de colheita de goiabas ‘Kumagai’ não interferiu na firmeza da polpa, no teor de sólidos solúveis e no ratio ao final do período comercializável, apresentando os frutos do estádio 1 mais verdes, com menor teor de ácido ascórbico e maior acidez titulável. Em goiabas ‘Paluma’, o ponto de colheita não influenciou na cor da casca e no teor de sólidos solúveis. No geral, os frutos do estádio 1 apresentaram-se mais firmes, com menor teor de ácido ascórbico, mais ácidos, com cor da polpa mais clara e maior ratio. Tanto a variedade Kumagai quanto a Paluma apresentaram pico respiratório e de produção de etileno, independente do estádio de maturação, porém, estes ocorreram após o completo amadurecimento dos frutos.
Guava is a highly perishable fruit and its post harvest physiology knowledgement is fundamental for the proper technology use in order to increase the preservation period. The present study was accomplished to determine the maturation rates; to verify the influence of the maturation levels in the post harvest and to determine the respiratory standard for the Kumagai and Paluma guavas. At first, the maturation rates and the influence of five levels of maturation in the post harvest of the fruit were determined. The fruits were selected in five levels of maturation according to the color of the peel: Level 1: a dark green color peel; Level 2: loss of the green color; Level 3: start of the yellow color of the peel; Level 4: a partially yellow color of the peel; Level 5: a totally yellow color of the fruits, and then, they were kept in a chamber at a percentage of 25 + 2ºC and 80-90% UR and evaluated as to the physico-chemical changes and sensory quality. After that, the respiration standard of the fruits was determined, analyzing the respiration activity, the production of ethylene and the physico-chemical changes after the harvest for the levels 1, 2 and 3. The color and the firmness of the peel were considered the best maturation rates for both varieties. The variety Paluma also showed the ratio as to a good maturation level. The physico-chemical variables showed less variation between the maturation levels after the ripeness, however significant differences were observed in relation to the sensorial analysis, obtaining the best performance for the levels 4 and 5 in the Kumagai variety and for the level 5 in the Paluma variety. The harvest point of the Kumagai guavas did nor interfere in the firmness of the flesh, in the content of the soluble solids and in the ratio to the end of the commerceable period, showing greener fruits in level 1 with a less content of ascorbic acid and a high titled acidic. In the Paluma guavas, the harvest point did not influence in the color of the peel and the content of soluble solids. In general, the fruits of level 1 showed firmer with a less content of ascorbic acid, more acidic with a lighter color of the flesh and a higher ratio. As the Kumagai as the Paluma varieties showed a respiratory peak and ethylene production independent of the maturation ratio, however these occurred after the complete ripeness of the fruits.

O mercado mundial de floricultura gera um fluxo de quase US$ 7bilhões anuais, atualmente concentrado em países como Holanda, Alemanha, Itália, Colômbia, Costa Rica, Equador, Quênia, Tailândia, Malásia, Israel e EUA. O Brasil ainda contribui pouco, aproximadamente 0,3% do total, sendo a participação brasileira concentrada na exportação de mudas, bulbos, flores e folhagens tropicais. O Brasil possui grande potencial exportador de flores e plantas ornamentais através da organização dos produtores, profissionalização do setor, apoio governamental e desenvolvimento técnico. O emprego de técnicas simples de armazenamento poderia viabilizar o transporte por modais que não o aéreo, reduzindo custos e podendo prolongar a vida útil dos produtos, criando um diferencial de qualidade em relação aos concorrentes. Este trabalho compara cinco diferentes tipos de recobrimento em estacas de Cordyline rubra Hügel (película amilácea, pasta de parafina no ápice, pasta de parafina no ápice e vermiculita umedecida na base, saco plástico ou sem recobrimento), sazonalidade (estacas coletadas durante primavera ou outono), dois ambientes de armazenamento (ambiente refrigerado a 10ºC ou temperatura ambiente 22-32ºC) e diferentes períodos de armazenamento (30, 60, 90 ou 120 dias), a fim de reduzir sua atividade biológica, perda de água e ataque de patógenos. Foi escolhida esta espécie por ser muito apreciada como planta ornamental devido à beleza de suas folhas, e exportada na forma de estacas de diferentes tamanhos. O experimento foi conduzido nas dependências do Departamento de Produção Vegetal da Escola Superior de Agricultura “Luiz de Queiroz”, Universidade de São Paulo, no município de Piracicaba, Estado de São Paulo. Foram utilizadas 615 estacas com 30 cm de comprimento por 3 cm de diâmetro. Um lote testemunha sem armazenamento de 15 estacas foi colocado em leito de enraizamento. Cada tratamento foi composto por 30 estacas pré-tratadas (tipos de recobrimento), submetidas a diferentes períodos de armazenamento (30, 60, 90 ou 120 dias), sendo divididos em 2 sub-tratamentos de 15 estacas (temperatura ambiente ou refrigerada), totalizando 120 estacas. Após o armazenamento foram cortados 3 cm da base de cada estaca, em seguida tratadas com IBA a 10.000 mg/L e colocadas em leito de enraizamento. Após 90 dias foram avaliados os seguintes parâmetros: porcentagem de desenvolvimento, número e massas de matéria fresca e seca de brotos, raízes e rizomas. Observou-se que as estacas colhidas na primavera apresentaram melhor enraizamento e produção de massas secas e frescas. Os menores períodos de armazenamento proporcionam melhor desenvolvimento das estacas, bem como estacas armazenadas em ambiente refrigerado apresentaram melhores resultados do que as mantidas em temperatura ambiente. Os tipos de recobrimento que melhor conservaram as estacas, em ordem decrescente de resultados, foram o saco plástico, parafina no ápice e vermiculita umedecida na base, parafina no ápice, película de amido e sem recobrimento. Conclui-se que o método mais prático foi embalar as estacas em sacos plásticos por não necessitar de fonte de calor para o preparo da película. Quanto maiores os períodos de armazenamento, menores desenvolvimentos de brotos, raízes e rizomas; os melhores resultados foram obtidos com estacas colhidas na primavera e armazenadas em ambiente refrigerado.
The world market of floriculture, generates an annual flow of US$ 7billion, is currently based on countries like The Netherlands, Germany, Italy, Colombia, Costa Rica, Ecuador, Kenya, Thayland, Malaysia, Israel and the USA. The Brazilian contribution to the total world market is approximately 0.3%, where the mains exports are cuttings, bulbs, tropical fresh cut flowers and foliages. Brazil, however, has a great potential to increase its export of flowers and other ornamental plants through the better organization of producers, professionalization of the sector, government support and technical development. The use of simple storage techniques, would enable the transport through other means than airplanes, consequently reducing costs and adding extra shelf life to the product, creating a quality differentiation in relation to competitors. This work was aimed at comparing five types of coating of Cordyline rubra Hügel cuttings (starch film, paraffin paste at the apex, paraffin past at the apex associated with moist vermiculite at the base of the cuttings, plastic bags or no coating), seasonality (cuttings harvested during spring or autumn), two types of enviromental temperatures (refrigeration under 10ºC or environmental temperature between 22-32ºC) and different lengths of time on storage (30, 60, 90 or 120 days), in order to reduce their biologycal activity, water loss and pathogen attacks. This specie is very appreciated as an ornamental plant due to the beauty of their foliage and is exported as cuttings of different sizes. The experiment was carried out at the Departament of Plant Production at “Luiz de Queiroz” College of Agriculture, University of Sao Paulo, in Piracicaba City, Sao Paulo State, Brazil. A total of 615 cuttings were used, each measuring 30 cm by 3 cm diameter. A control group of 15 cuttings without storage was planted on rooting bed. Each treatment was comprised of 30 pre-coated cuttings (types of coating), stored at different periods (30.60, 90 or 120 days) and split into 2 sub-treatments of 15 cuttings, either stored at room temperature or under refrigeration, summing up 120 cuttings. After storage, each cutting had 3 cm excised from its base, prior to being treated with IBA 10.000 mg/L and placed at rooting beds. After 90 days, the following parameters were assessed: percentage of cuttings showing growth and development, number and fresh and dry matter of the shoots, roots and rhizoms. It was observed that cuttings obtained during the spring, showed better rooting and production of biomass. The shorter the storage periods the better the cutting sprouting. Cuttings stored under refrigeration showed better results than kept under room temperature. The types of coatings which best supported the longevity of the cuttings, in decrease order, were: plastic bag, paraffin paste at the apex and moist vermiculite at the base, paraffin on the apex, starch film and no coating. Such results allow to conclude that the most practical coating technique was found to be the use of plastic bags, which did not need heating for the prepare of the film. The longer the storage time the smallest the number of viable cuttings; best results where observed for cuttings harvested during the spring and kept under refrigeration storage.

Este trabalho teve por finalidade avaliar os efeitos de temperatura nos metabolismos de couves-flores e rúculas inteiras e minimamente processadas e diferentes materiais de embalagem na sua qualidade. No primeiro experimento, couves-flores, seus floretes, rúculas e suas folhas foram mantidos a 1º, 5º e 11ºC e determinados suas taxas de respiração, produção de etileno e quocientes de temperatura (Q10). No segundo, os floretes foram colocados em embalagens de filmes de polietileno de baixa densidade (PEBD), poliolefínicos coextrusados (PD – 941 e Clysar) e de policloreto de vinila, PVC esticável de 12 e 20 mm, envolvendo bandejas de poliestireno expandido mantidos a 5ºC. Análises físicas, químicas, físico-químicas, microbiológicas e sensoriais foram realizadas. No terceiro, folhas de rúculas foram colocadas em embalagens de filme de polietileno de baixa densidade (PEBD), laminado de polipropileno/polietileno (PP/PE), poliolefínicos coextrusados (PD – 900 e Clysar) e de policloreto de vinila, PVC esticável de 20 mm, envolvendo bandejas de poliestireno expandido e armazenados a 5ºC. Análises físicas, químicas, físico-químicas, microbiológicas e sensoriais foram realizadas. As taxas respiratórias das couves-flores inteiras e minimamente processadas foram iguais em quaisquer das temperaturas estudadas e sempre decrescentes até o 16º dia. A 1º e a 5ºC, tiveram a mesma taxa respiratória, diferindo das mantidas a 11ºC. Na faixa de 1º a 11ºC, o Q10 foi o mesmo para floretes e couves-flores; 2,1 e 2,2, respectivamente. Comportamento distinto tiveram as rúculas inteiras e as folhas soltas, pois, a 1ºC e a 5ºC, as taxas respiratórias foram significativamente iguais. A 11ºC, a partir do 4º dia, as folhas soltas começaram a apresentar taxas de respiração superiores às das inteiras, chegando a ser o dobro nos 14º e 16º dias de armazenamento. O Q10 médio para as rúculas inteiras situou-se ao redor de 3,54 e para as folhas soltas, 5,74, na faixa de 1º a 11ºC. Não foi detectada produção de etileno. As embalagens para floretes de couves-flores tiveram pouca ou nenhuma influência em seu pH, acidez, ºBrix, luminosidade, croma, Hue e firmeza. A embalagem PD – 941 foi a melhor por manter uma atmosfera modificada próxima à da recomendada para couves-flores (2-3% O2 e CO2 < 5%) e permitir menores perdas de vitamina C e melhores notas para vários atributos sensoriais de qualidade. Todas as embalagens mantiveram níveis de coliformes totais, bolores e leveduras bem abaixo dos limites permitidos pela Legislação Brasileira. As folhas de rúculas apresentaram níveis de coliformes totais ao redor de 10 5 UFC/g de produto no 10º dia a 5ºC, tornando-as impróprias para o consumo. Nestes 10 dias, as embalagens de PEBD e PP/PE se destacaram em relação às outras por reterem melhor a vitamina C e a coloração verde das folhas, por alcançarem melhores valores para sólidos solúveis, firmeza, presença de odor estranho, qualidade geral das folhas, deterioração e murchamento. As atmosferas modificadas desenvolvidas no interior destas embalagens, 5 a 7% O2 e 10 a 15% CO2, talvez sejam as mais indicadas para a conservação de rúculas minimamente processadas a 5ºC.
This work aimed at evaluating the effects of temperature on the metabolism of minimally processed and intact cauliflowers and salad rockets, and of different packaging materials on the quality of cauliflower florets and loose salad rocket minimally processed leaves. In the first experiment, intact cauliflowers, florets, intact salad rockets and loose salad rocket leaves were held at 1º, 5º and 11ºC and their respiration rates, ethylene production and temperature quotients (Q10) determined. In the second experiment, the florets were packed in low density polyethylene film (PEBD), co-extruded polyolefins (PD – 941 and Clysar AFG) and in 12 and 20 mm polyvinyl chloride (PVC) overwrapping expanded polystyrene trays, and maintained at 5ºC/85-95% relative humidity for 14 days. In the third experiment, loose salad rocket leaves were held under the same conditions in bags of low density polyethylene film (PEBD), laminated polypropylene/polyethylene film (PP/PE), co-extruded polyolefins, PD – 900 and Clysar HP and in expanded polystyrene trays overwrapped with 20 mm polyvinyl chloride (PVC). In the second and third experiments, physical, chemical, physical-chemical, microbiological and sensory analyses were performed. The respiration rates of both intact and fresh-cut cauliflowers declined over the 16-day period and were significantly the same at all temperatures studied. At 1º and 5ºC the respiration rates were the same but differed from those (cauliflower and florets) at 11ºC. From 1º to 11ºC, the Q10 for the cauliflowers was 2.2 and for the florets, 2.1. In contrast, the intact and fresh-cut salad rocket respiration rates were the same at 1º and 5ºC. At 11ºC, the fresh-cut salad rocket showed higher respiration rates than the intact ones as from the 4 th day. By the end of the experiment (14 th and 16 th days) the respiration rates of the fresh-cut salad rockets were twice those of the intact salad rockets, whose Q10 was about 3.45 from 1° to 11°C as compared to 5.74 for the fresh cut product. No ethylene production was detected by any sample at any temperature. The packaging materials had little or no effect on pH, titratable acidity, soluble solids, luminosity, chroma, hue and firmness of the florets at 5ºC. PD – 941 seemed to be the best packaging for florets, maintaining the atmosphere closest to that recommended for intact cauliflower (2-3%O2, CO2 < 5%), showing the lowest vitamin C losses and the best scores for several of the quality attributes. In general, all the packaging materials kept the yeast and mold counts low and the total coliform counts far below the maximum values permitted by the Brazilian Legislation, during 14 days at 5ºC, except for fresh-cut salad rocket leaves, which presented 10 5 CFU/g total coliforms by the 10 th day, being inappropriate for consumption. For 10 day periods, PEBD and PP/PE were the best packaging materials for green color and vitamin C retention, higher soluble solids, firmness, lack of off-odors, overall quality, decay and shriveling. The modified atmosphere generated inside these packaging materials (5-7% O2, 10-15% CO2) seemed the best for maintaining the quality of fresh-cut salad rockets held at 5ºC.

碩士
國立臺灣大學
園藝學研究所
96
Since the commercialization of first transgenic crop in 1996, safety of genetically-modified crops and its related products become major concerns of consumer. Currently, environmental risk assessment brings by transgenic crops and food safety are the two main issues worldwide. To meet global regulatory authorities on the practice of substantial equivalence on transgenic food, which means that food derived from crops produced through biotechnology be as safe as food produced from conventionally bred crops, this study has investigated the variations of the gene expressions and protein accumulations in transgenic tomato fruits throughout the post-harvest and processing processes. We used Southern blotting and real-time PCR to verify single copy of CMV coat protein gene found within the genome of the transgenic tomato lines in this experiment. Comparison of seven ripening-related gene expressions between genetically modified (GM) and non-GM tomato fruits at different ripening stages by real-time quantitative PCR were also carried out. No significant differences were found in seven ripening-related gene expressions among GM and Non-GM tomato fruits at the same ripening stage. Furthermore, the expression of exogenous gene - CMV coat protein showed no significant changes in GM tomato fruit among different ripening stages. Detection of CMV coat protein among different ripening stages of transgenic tomato fruits is done by Western blotting. The CMV coat protein accumulations is extremely low in transgenic tomato fruits. The limitation of colorimetric detection was about 0.1 μg of purified CMV coat protein. We further compared with exogenous gene and ripening-related gene expressions among GM tomato fruits. The CMV coat protein gene transcripts were significantly lower than ripening-related gene transcripts. Therefore, it is presumed that post-transcriptional gene silencing mechanism may be the reason of anti-virus ability in transgenic tomato. Subsequently, two-dimensional electrophoresis was used to analysis the differential accumulations of total proteins among GM and Non-GM tomato fruits. The results indicated that there were some differential accumulations of proteins between GM and Non-GM tomato fruits. However the differential expression of proteins may be due to the environmental changes or experiment manipulation errors. Therefore, further study should focus on the properties of the differential proteins using western blotting or mass spectrometry.

碩士
國立屏東科技大學
農園生產系所
96
Postharvest physiology of ‘TN11’、‘TN17’ and ‘TN18’ pineapple (Ananas comosus (L.) Merr.) fruit collected from Wu’s orchard, Ma-Chia, Pingtung county, were studied. A series of studies including postharvest physiology, packaging with polyenhtlene (PE) bag, chemical treatments, various maturity, temperature and fruit components were conducted. The result showed that respiration and ethylene of three pineapple cultivar increased with storage temperature. The pineapple fruit exhibited typical non-climacteric fruit identified by no climacteric respiratory and ethylene peak. The ‘TN18’ fruit packaged with sealed PE bag containing ethylene absorbents at 15℃, extended storage life (about 31.7 days) significantly. No significant difference on storage life of packaged and unpackaged ‘TN11’ and ‘TN17’ fruit. The storage life of ‘TN17’ and ‘TN18’ fruit soaked with 25％ ClO2 for 1 minute were 36.0 and 33.7 days and significantly different from control. However, there is no significant effect on storage life of ‘TN11’ fruit soaked with ClO2. Total soluble solids (TSS), titratable acidity (TA), sugar/acid ratio and peel hue angle (θ) of pineapple fruits were decreased with storage. Vitamin C levels at harvest and storeage of ‘TN18’ were significantly higher than the other two pineapple cultivar. Besides, pH value, moisture content of pulp, lightness and chroma of peel were increased with storage time. All cultivar tested showed fruit harvested at 1/4-yellow shell color stage had best storage life at 15℃(about 36.7, 34.0 and 29.0 days, respectively for ‘TN11’, ‘TN17’ and ‘TN18’). No significant difference on quality in storage between fruit harvested at half-yellow and 3/4-yellow shell color stage. Maturity at 1/4-yellow shell color stage and 15℃ in storage were suggested to extend storage life and quality in transportation of pineapple fruits. Among the three pineapple cultivar studied, ‘TN17’ was most susceptible to chilling injury (blackheart) and followed by ‘TN18’ and ‘TN11’. Both ‘TN17’ and ‘TN18’ cultivar expressed blackheart symptoms at 25℃ when stored beyond 9 days at 15℃. The susceptibility of pineapple fruit to chilling injury increased with maturity. There was variation of flavor among pineapple fruit parts. The TSS, sugar/acid ratio and pH value increased from crown end to basal tissue and TA levels showed inverse trend. After harvest, the sucrose content was the highest (9.104 g/100g) and flowed by fructose (3.480 g/100g) and glucose (2.634 g/100g). Maltose was not detected.

碩士
國立屏東科技大學
農園生產系
94
A series of studies were conducted to elucidate the physico-chemical changes during postharvest packagings : unpackage, sealed in polyethylene (PE) bag, sealed in PE bag containing ethylene absorbents, perforated PE bag, torsional PE bag containing polystyrene net sleeve (PNS), sealed in PE bag containing PNS, sealed in PE bag containing PNS and ethylene absorbents. Different thickness (0.03、0.05mm) of PE bag lining packaging treatments, heat treatments (8、12 and 16sec. at 46℃ and 8、12sec. at 48℃), PE (pectinesterase) and PG (polygalacturonase) activity of two cultivars of guava fruits (Psidium guajava L.), named ‘Jen-Ju Bar’ and ‘Shui-Jing Bar’ during storage were also investigated. Results showed that the ‘Jen-Ju Bar’ and ‘Shui-Jung Bar’ fruits were stored at different temperatures (0-25℃) , there were not appeared clearly climacteric respiration and ethylene peak. After stored at 0-25℃, the weight loss of unpackaged fruits were significantly higher than other package, secondly were perforated PE bag packaged fruits, and the fruits packed with PE bags were significantly lower. The weight loss were reduced with the lowering the storage temperature. However, guava fruits storing at low temperatures exhibited surface pitting and browning symptoms of chilling injury (‘Jen-Ju Bar’ , 0℃10 days and 5℃20 days ; ‘Shui-Jing Bar’ , 0℃4 days and 5℃6 days). Fruits packed with sealed in PE bag containing PNS and sealed in PE bag containing PNS and ethylene absorbents would delay and alleviate the development of chilling injury. The rate of chilling injury of ‘Jen-Ju Bar’ fruits were lower than ‘Shui-Jing Bar’ fruits, and the time of chilling injury symptom appeared of ‘Jen-Ju Bar’ was also late. Therefore, guava fruits should be stored at 5℃during storage and transportation. In addition, different packaging methods affected storage life of fruits. The fruits of ‘Jen-Ju Bar’ packed with sealed PE bag containing PNS and sealed in PE bag containing PNS and ethylene absorbents at 5℃were significantly extended the storage life to 33-34 days；‘Shui-Jing Bar’ fruits were 20 days. Using different thickness of PE bag lining in carton of ‘Jen-Ju Bar’ and ‘Shui-Jung Bar’ fruits, regardless of 0.03mm or 0.05mm of PE bag linings, fruits stored at 25℃with vacuum sealed in PE bag lining produced off-flavor and decay. But fruits stored at 5℃with vacuum sealed in PE bag lining had the longest storage life (‘Jen-Ju Bar’, 33 days and ‘Shui-Jing Bar’, 25-26days). Fruits quality among those of fruits, with it used regardless of thickness of PE bag lining or vacuum sealed treatments, were no significantly different. Prestorage heat treatments of ‘Jen-Ju Bar’ and ‘Shui-Jung Bar’ fruits stored at 5、10℃, the respiration rate of two cultivars fruits were increased slowly compared to untreatment fruit, the respiration rate of fruits stored at 10℃ was higher than stored at 5℃. The lower ethylene production rate of ‘Shui-Jing Bar’ fruits with heat treatments (12sec. at 48℃) stored at 5℃ and (12sec. at 46℃) stored at 10℃. On the quality of guava fruits, the fruit firmness and crispness retained after heat treatments, and did not affect total soluble solids, titratable acidity, pH value and Vit. C of the fruits, and delay yellowing of peel color. Moreover, could extend their storage life and delayed and alleviated chilling injury and decay incidence. Two cultivars of guava fruits ‘Jen-Ju Bar’ and ‘Shui-Jing Bar’ during storage, the enzyme activity of PE and PG were higher at 25℃than those of fruits stored at 5℃and 10℃. Regardless of package, PE and PG activity of fruits increased during storage and the effect of packagings on both enzymes activity were smaller than its effects on weight loss and firmness.

碩士
國立屏東科技大學
農園生產系
94
Two varieties of dragon fruits (Hylocereus spp.) `cv. white pulp' and `cv. red pulp' from Lin’s Farm in Changchih, Pingtung were used in this study. A series of studies were conducted to elucidate the physicochemical changes, sugar contents during fruits development, postharvest storage (0-25℃). Five packaging types were compared in this study: unpackaged, tensional PE bag, sealed in polyethylene (PE) bag, sealed in PE bag containing ethylene absorbents, and sealed in PE bag containing polystyrene net sleeve (PNS). Quarantine of quality at low temperature (0℃, 15 days) was investigated. The results showed that the respiration rate of both white and red pitaya fruits were typical non-climacteric pattern during fruits development and post harvest storage. The respiration rate of both varieties was increased at initial growth period (10-20 days), and respiratory rate was subsequently decreased in later growth period. The white pitaya respiration rate was peak at 15th day after onset of fruit, but the red pitaya was 20th day after onset of fruit. The ethylene production rate was high at the early stage and decreased gradually as the pitaya fruit increase in size. The ethylene production rates of the red pitaya were higher than the white pitaya. In addition, the ethylene production rates of white pitaya and red pitaya were both low at later growth period. No significant climacteric respiration or ethylene peak observed during fruit development. Results showed that the growth curves of fresh weight, length, width and volume of dragon fruits development were in a typical single sigmoid pattern. The ratio of fruits total soluble solids (TSS), fruit flesh percent, dry matter of fruit flesh and seedcase increased progressively with the days after bloom. However, the firmness, titratable acidity (TA), the skin of fruit thickness and percent, and fruit flesh contain water percent ratio decreased with the increased of the duration of growth. The fruits lightness and hue angle values decreased with color changed on 25 days, but chrome values increased. The skin color of both pitaya was red. The storage life of the white pitaya fruits with sealed in PE bag containing PNS was 37 days at 0℃, the red pitaya fruits was 35 days, while the fruits still possessing commercial value. The dragon fruits stored at 5℃ did not show symptoms of chilling injury. The storage life of the white pitaya fruits was 31 days at 5℃, but the red pitaya fruits were 27 days. The TA content of dragon fruits increased with the increase of storage duration at 0-5℃. The TSS/acidity ratio of fruits decreased with the increase of storage duration at 0-5℃. The dragon fruit quality in TSS, TA and retained the vitamin C content decreased with the increase of storage duration at 10-25℃. The TSS/acidity ratio of fruits increased with the increase of storage duration at 10-25℃. Various packaging methods had no impact to the fruit quality during post harvest storage period. The contents of TSS were high in core of the mature fruits of `cv. white pulp' and `cv. red pulp’, but the contents of TA were low. Therefore, the TSS/acidity ratio was high in core of the fruits, but the TSS/acidity ratio was low in near skin of fruit. The major sugars of dragon fruits were fructose, glucose and maltose, no sucrose. When the `cv. White Pulp' and `cv. Red Pulp' fruits were first stored at low temperature quarantine treatment (0℃, 15 days), then transferred to 10℃ and 25℃, the chilling injury on the fruit surface was observed at 10℃ for six days. The firmness, pH and TSS/acidity ratio of dragon fruits increased with the increase of storage temperature at 0℃, and the stored pitaya fruits appeared corruptible at 25℃.

碩士
國立屏東科技大學
農園生產系所
97
The study was to investigate the fruit postharvest physiology, quality and the effect of hole number of perforated PE bag in carton on peel color during ripening of two Taiwan major banana cultivars, ‘Pei- Chiao’ (traditional commercial cultivar) and ‘Formosana’ (resisting banana fusarium wilt and high yield cultivar selected from ‘Pei- Chiao’ tissue culture plants) were packed by following perforated PE bag treatments: control (no PE bag), 48-hole PE bag, 64-hole PE bag, 80-hole PE bag, and 96-hole PE bag within cardboard carton. The PE bag thickness in this experiment was 0.035 mm except 48-hole PE bag was 0.02mm. The materials of banana were harvested from Taiwan Banana Research Institute which produced following Taiwan Good Agriculture Practice (TGAP). Fruit quality of banana at different hands in the same bunch and at different sites (left, middle and right) of fingers in a same hand were also compared. Results showed the respiration rate of banana fruits during pre-climacteric period of ‘Pei- Chiao’ stored in 15, 20 and 25℃ were 11.29, 12.86 and 19.65 mgCO2/Kg-hr; and ‘Formosana’ were 13.47, 13.19, and 21.90 mgCO2/Kg-hr, respectively. During storage, the respiration rate increased with increased storage temperature. The respiration rate of ‘Pei- Chiao’ was slight lower than that of ‘Formosana’. The time of climacteric rise were not different (ca.32 days) between the two cultivars when storage in 15℃. However, storage in 20 and 25℃, the climacteric rise of ‘Pei- Chiao’ appeared earlier (ca. 2 days in 20℃ and 7 days in 25℃) than ‘Formosana’. In storage, the ethylene production during pre-climacteric period of ‘Pei- Chiao’ and ‘Formosana’ were 0.06-0.08 μl/kg-hr and 0.07-0.11 μl/kg-hr respectively. The peak of respiration rate and ethylene production rate of ‘Pei- Chiao’ were earlier than those of ‘Formosana’. The ‘Pei- Chiao’ showed a faster degreening rate than that of ‘Formosana’. Packaging treatments showed the firmness of fruits with peel packed with perforated PE bag were lower than those without packed fruits in both cultivars. However, the PE packaging didn’t affect pulp firmness in the two cultivars. The total soluble solids content and sugar/acid ratio of bananas packed by perforated PE bag were higher than those of control and especially significantly higher in ‘Formosana’. The lightness of fruits packed with PE bag were significantly higher than those of control. The hue angle of packed fruits were significantly lower than those without packed fruits and the peel color were more yellow. The degreening of peel color of control reached to color index 4 (more yellow than green) was 5 and 6 days for ‘Pei- Chiao’ and ‘Formosana’, respectively. However, the degreening rate were enhanced by PE packaging. The degreening rate of ‘Pei- Chiao’ packed by 48-hole PE bag was 4 days and shortened about 1 day than those without packed. That also shortened 1 day in ‘Formosana’ packed by 48-hole PE bag. However, the degreening rate of ‘Formosana’ packed by 64-hole,80-hole and 96-hole PE bag were 4 days and the same as ‘Pei- Chiao’ packed by 48-hole PE bag. There were no difference in shelf life between these two cultivars. The first to third hand were heavier than other hand in same bunch and decreased from fourth to distal hand. The total soluble solid content, titratable acidity, pH value and sugar/acid ratio of different hands on same bunch were not significantly different. The content of titratable acidity of ‘Formosana’ was higher than ‘Pei-Chiao’ and sugar/acid ratio was reversed. Fruit and pulp firmness in different hands were not significantly different. The fruit firmness of ‘Pei-Chiao’ were lower than ‘Formosana’, but the pulp firmness were not different between the two cultivars. The peel color (lightness, hue angle and chroma) among different hands or cultivars were not significantly different. The quality (total soluble solid, titratable acidity, pH value, firmness, color, fruit weight, pulp weight and peel weight) were not different in different sites (left, middle and right) of fingers of same hand in ‘Pei-Chiao’ and ‘Formosana’. Sucrose were the major soluble sugars of ‘Pei-Chiao’ and ‘Formosana’ fruit after ripening. It account for 66.5-71 % of soluble sugars in fruit and follows by glucose (15.4- 17.8%) and fructose (14.1-16.5%). The ratio of fructose : glucose : sucrose was 1.0 : 1.0-1.2 : 4.0-4.9

The current state of global biodiversity is one of sustained and increasing decline especially in developing countries such as South Africa, where, medicinal plants face a particular threat due the herbal medicine trade, and because in situ conservation measures have not stemmed the exploitation of these plants (Chapter 1). Furthermore, seed storage, which offers an efficient ex situ conservation technique, cannot presently be applied to many medicinal plants, either because these species produce short-lived, recalcitrant seeds, or the post-shedding behaviour of the seeds is altogether unknown. This study investigated three medicinal plant species indigenous to Kenya and South Africa: Trichilia dregeana and T. emetica, of which no population inventories exist and no wild populations were encountered locally during the course of this study; and Warburgia salutaris, one of the most highly-utilised medicinal plants in Africa, and which is currently endangered and virtually extinct in the wild in some countries such as South Africa. Aspects of post-shedding seed physiology (Chapter 2) and the responses of the germplasm of the three species to cryopreservation (Chapter 3) were studied using viability and ultrastructural assessment, with the aim of establishing methods for both short-term and the long-term preservation, via appropriate seed storage and cryopreservation, respectively. The effect of cryopreservation on genetic fidelity, a crucial aspect of germplasm conservation, was assessed by polymerase chain reaction (PCR) based random amplified polymorphic DNA (RAPDs), using W. salutaris as a case-study (Chapter 4). The seeds of all three species were found to exhibit non-orthodox behaviour. On relatively slow-drying, seeds of T. dregeana and T. emetica lost viability and ultrastructural integrity at axis water contents of 0.55 g g-l (achieved over 6 d) and 0.42 g g-l (after 3 d) respectively, while flash-drying of embryonic axes facilitated their tolerance of water contents as low as 0.16 g g-l (T. dregeana, flash-dried for 4 h) and 0.26 (T. emetica, flash-dried for 90 min). Seeds of W. salutaris were relatively more tolerant to desiccation, remaining viable at axis water contents below 0.1 g g-l when desiccated for 6 d in activated silica gel. However, excised embryonic axes flash-dried to similar water contents over 90 min lost viability and were ultrastructurally damaged beyond functionality. In terms of storability of the seeds, those of T. dregeana could be stored in the fully hydrated state for at least 5 months, provided that the quality was high and microbial contamination was curtailed at onset of storage, while those T. emetica remained in hydrated storage for about 60 d, before all seeds germinated in storage. Seeds of W salutaris, even though relatively tolerant to desiccation, were not practically storable at reduced water content, losing viability within 49 d when stored at an axis water content of 0.1 g g-l. The seeds of all three species were sensitive to chilling, suffering extensive subcellular derangement, accompanied by loss of viability, when stored at 6 °C. Thus, T. dregeana and T. emetica are typically recalcitrant, while those of W. salutaris are suggested to fit within the intermediate category of seed behaviour. For either recalcitrant or intermediate seeds, the only feasible method of long-term germpalsm preservation may be cryopreservation. Subsequent studies established that whole seeds of W. salutaris could be successfully cryopreserved following dehydration in activated silica gel. However, whole seeds of T. dregeana and T. emetica were unsuitable for cryopreservation, and excised embryonic axes were utilised. For these, in vitro germination methods, as well as cryoprotection, dehydration, freezing and thawing protocols were established. Post-thaw survival of the axes of both species was shown to depend on cryoprotection, rapid dehydration and cooling (freezing) in cryovials. Embryonic axes of T. dregeana regenerated only as callus after cryopreservation, while those of T. emetica generated into apparently normal plantlets. Thawing/rehydration in a 1:1 solution of 1 µM CaC12.2H2O and 1 mM MgC12.6H2O increased the percentage of axes surviving freezing, and that of T. emetica axes developing shoots. The effect of the extent of seed/axis development on onward growth after cryopreservation was apparent for seeds of W. salutaris and excised axes of T. emetica. The seeds of W. salutaris surviving after cryopreservation germinated into seedlings which appeared similar to those from non-cryopreserved seeds, both morphologically and in terms of growth rate. Analysis using PCR-RAPDs revealed that there were no differences in both nucleotide diversity or divergence, among populations of seedlings from seeds which had been sown fresh, or those which had either been dehydrated only, or dehydrated and cryopreserved. Thus, neither dehydration alone, nor dehydration followed by cryopreservation, was associated with any discernible genomic change. The above results are reported and discussed in detail in Chapters 2 to 4, and recommendations and future prospects outlined in Chapter 5.
Thesis (Ph.D.)-University of Natal, Durban, 2002.

碩士
國立屏東科技大學
農園生產系
93
The series of study were conducted to elucidate the physico-chemical changes during fruit growth and development, postharvest packaging and storage, the respiration and ethylene production, and their responses to 1-MCP(1-methylcyclopropene) of two cultivars of Indian jujube (Zizyphus mauritiana Lam.), named ‘Koulan No3’ and ‘Mitzau’ were investigated. Results showed that the growth curves of fresh length、width、weigt, and volume of fruit were in a double sigmoid growth curve.The growth and develop of jujube fruit developed into maturation stage at 100-105 days after fruit set. At this stage, the fruit length and width, fresh weight, and volume reached nearly their maximum, the peel color changed rapidly from green to light green or yellowish green. As for chemical constituents, total soluble solid content, sugar/acid ratio and Vit.C content increased rapidly and reduced in titratable acidity during maturation stages. Indian jujube fruits, including ‘Mitzau’ and ‘Koulan No.3’，are typical climacteric fruits. The only difference will be the time of the peaks appeared and the production rate. When the fruits of ‘Mitzau’ and ‘Koulan No.3’ were stored at 0-25℃, the weight loss of fruits during storage were the most serious (about 8-13%) in naked, unpackaged fruits, and the least (about 0.2-0.4%) in the fruits packed with sealed PE bags, sealed in PE bags containing ethylene absorbents or vacuum packed with PE bags .The weight loss significantly increased with the increase of the storage temperature.The fruits qualities in titratable acidity and TSS were lower, but peel hue angle (θ) was higher in PE packaged fruits.The storage life of Indian jujube (cv. ‘Mitzau’ and ‘Koulan No.3’) stored at different temperatures (0-25℃), the storage life of the naked, unpackged fruits were 4-8 days, and increased significantly with lowering temperature. The longest storage life of fruits were stored at 5℃, the ‘Mitzau’ had about 30 days storage life and ‘Koulan No.3’ had about 24 days at 5℃.However, the storage life (about 28-33days)of fruits packaged with sealed PE(0.03mm) bag (including PE bag containing ethylene absorbent or vacuum packed) were also significant longer than those of naked fruits or perforated PE bag fruits. Indian jujube fruits storing at 0℃ for 7-11days exhibited surface pitting and browning symptoms of chilling injury. Therefore, Indian jujube fruits are suitable storage at 5℃ with sealed PE bags. At different storage temperatures(0-25℃) , there were exhibited climacteric respiration peak and ethylene peak, and there were clearly climacteris rise in 20℃or 25℃and exhibited typical climacteric pattern. The respiration rates and ethylene production increased with the increase of the temperature and the climacteric peak occurred were earlier with the increase of the temperature. The total soluble solid (TSS) at different parts of tissue of Indian jujube fruits(cv. ‘Mitzau’ and ‘Koulan No.3’) were determined. The near the apex tissues of fruit, the higher TSS. Furthermore, the near the skin of fruit, also the higher TSS . The TSS at different parts of tissues of ‘Mitzau’ fruit were significantly higher than those of ‘Koulan No.3’cultivar. Using 0.03mm or 0.05mm PE packed of Indian jujube fruits (cv.‘Mitzau’and ‘Koulan No.3’ ), regardless of sealed or not, their storage life and quality were significantly affected, especially, with 0.05mmPE packed. During three weeks storage at 5℃, vacuum packed of 0.05mm PE produced off-flavor, and were severely with the increase of the storage duration. Obviously, vacuum packed of 0.05mm PE is not suitable on Indian jujube fruits. The respiration and ethylene production rate were lower in ‘Mitzau’ fruit treated with 0.1 or 1ppm 1-MCP for 12hrs or 24hrs at 10℃or 25℃and stored at same temperatures. During storage, the titratable acidity and vitamin C content and peel lightness (L) lower than those of control fruits, but fruit firmness and peel hue angle (θ) were higher. Results showed that Indian jujube fruits treated with 1-MCP, were higher in firmness and retained more green color.

Apples stored onshore in Australia and New Zealand, are maintained at optimal storage conditions with the aid of low temperatures; controlled atmospheres (CA) and new technologies that retard the production or effect of ethylene (AVG and 1-MCP respectively). These technologies allow distribution of the highest quality apples to local and export markets on a year round basis. However, during distribution, maintenance of optimal storage conditions may be lost due to refrigeration system breakdown, operational constraints or management decisions. This thesis quantifies the influence of commercially realistic breaks in optimal storage conditions (temperature and CA) on fruit physiology and quality, both at the time of the break and in subsequent optimal storage conditions. The ‘Cripps Pink’ (‘Pink Lady™’) apple cultivar was chosen for consideration in this thesis because it is a high value cultivar that is of considerable importance to the Australian apple industry. The knowledge of the behaviour of ‘Cripps Pink’ apples in coolstorage conditions (in air and CA) was confirmed through comparison of physiological and quality change behaviour of fruit from three harvests collected in this research and those reported recently by other authors. The investigation of the influence of breaks in temperature control during storage in air at 0°C, revealed that preclimacteric apples exposed to a break in temperature control, were advanced towards the establishment of the climacteric. Postclimacteric apple, responded by doubling ethylene production a short time after return to coolstorage. Harvest maturity, timing of break during coolstorage, length of break of temperature control and multiple breaks in temperature control, had little influence on the increase ethylene production response. Quality factors (firmness, background hue angle, and titratable acidity) were all reduced as a result of exposure to warmer temperatures, but on return to coolstorage temperatures rates of loss in these quality factors were not influenced by the increased ethylene production. Short-term (3-day) breaks in CA while fruit remained at refrigerated temperatures were shown to have no substantial effect on fruit physiology or quality, either during the period of the break in CA or in subsequent CA storage. Breaks in temperature control in combination with breaks in CA were observed to cause a doubling of ethylene production on CA stored apples regardless of being returned to 0°C in air or CA. Those apples that were exposed to a break in temperature control and returned to air storage at refrigerated temperature lost quality (firmness and background hue angle) more rapidly than apples not exposed to breaks in temperature control and transferred to air storage. This result strengthened the knowledge of the influence of ethylene on changes in apple quality, as found for many other apple cultivars. The influence of the decision to transport fruit in CA or air atmosphere shipping containers was initially investigated with a laboratory simulation. Physiology (respiration rate and ethylene production) of air shipped fruit was found not only to be more rapid, but more variable between fruit, than for apples shipped in CA. This more rapid and larger variation of possible fruit physiologies, suggests that in addition to losing quality at a faster rate, the variation in the quality of fruit shipped in air will also enlarge during shipment. This hypothesis was confirmed with data pooled from treatments subjected to 0°C and 3°C, simulating the likely temperature variability within a shipping container. Validation of the influence of shipping atmosphere on delivered fruit quality, was conducted in the commercial environment. This trial found that the length of time to ship fruit from Australia and New Zealand to European markets was not sufficient to induce commercially significant differences between ‘Cripps Pink’ apples shipped in the two atmospheres. Finally, as ethylene production was influenced by fluctuations in temperature control and subsequently affected quality of apples previously stored in CA, an investigative attempt to model ethylene production in temperature variable scenarios was conducted. Published models of ethylene production in apples were adapted to the variable temperature storage scenario and a new model was proposed. Unfortunately, none of the models investigated were able to predict all of the consistent behaviours of ethylene production observed during the experimental work, indicating that more knowledge of the ethylene production pathway is required, before modelling of ethylene production and subsequently apple quality can be conducted successfully.

碩士
國立屏東科技大學
熱帶農業暨國際合作研究所
91
A series of studies were conducted to elucidate the physico-chemical changes during fruit growth and development, and postharvest physiology and storage of three cultivars of papaya fruits (Carica papaya L.), named ‘Tainung No.2’, ‘Sunrise’, and ‘SR-mu’ (a newly selected line and has yet to be named), and their responses to 1-methylcyclopropene (1-MCP) and heat treatments. Results showed that the growth curves of fresh weight, volume, length, and width of fruits were in a typical single sigmoid pattern. The fresh thickness, seed weight, dry matter, vitamin C, total soluble solids (TSS) and sugar/acid ratio increased progressively with the days after pollination. However, the firmness, moisture content of fruit, and hue angle of peel and flesh decreased with the fruit growth and development. Papaya fruits, including ‘Tainung No.2’, ‘Sunrise’ and‘ SR-mu’ cultivars, are typical climacteric fruits. During the growth and development, fruits at different stages (ages) all exhibited climacteric respiratory and ethylene production peak at 20 oC after harvest. The only difference will be the time of the peaks appeared and the production rate. For example, the 130-day old fruits, the peak of respiration of ‘Tainung No.2’ fruits appeared on the fifth day at the rate of 42.13 mg CO2/kg-hr and the peak of ethylene production was found on the sixth day with a production rate of 3.87 µl/kg-hr. The peak of respiration of Sunrise fruits appeared on the fourth day at the rate of 40.96mg CO2/kg-hr and the peak of ethylene production was found on the seventh day with a production rate of 4.82 µl/kg-hr. The peak of respiration of ‘SR-mu’ fruits appeared on the sixth day at a rate of 42.35 mg CO2/kg-hr and the peak of ethylene production was also found on the seventh day with a production rate of 3.61µl/kg-hr. The peak of climacteric ethylene production usually appeared one to two days later than the peak of climacteric respiration. In these three cultivars, the concentrations of CO2 and ethylene in fruit cavities were not detectable before 105 days after pollination. Only until 120 days after pollination, CO2 and ethylene were clearly detected in the Sunrise fruits at a concentration of 5.92 % and 0.06 ppm, respectively, and in ‘Tainung No.2’ fruits were 3.98 % and 0.02 ppm, respectively. Although CO2 was also detected in ‘SR-mu’ at a concentration of 1.32 % in 120 days after pollination, but ethylene was detectable at a concentration of 0.09 ppm in 130 days after pollination. CO2 and ethylene concentrations reached their peaks in the fruit cavity of the three cultivars in 130-135 days after pollination. Afterwards, the more mature the fruits became, the lower the concentrations of CO2 and ethylene detected in fruit cavities. At the different maturities of papaya fruits (‘Tainung No.2’), the respiration rate of fruits increased with the increase of the storage temperature, and the time for climacteric rise of respiration and ethylene production were shortened. In addition, the higher the maturity of the fruits, the time for the climacteric respiration and ethylene production peak were earlier, and the rate at peak were higher with the more mature fruits. When the fruits of ‘Tainung No.2’ and ‘Sunrise’ were stored at 5-25oC, the weight loss in naked, unpackaged fruits was most serious; reaching 11-15 % in nine days storage. The weight loss was the least (about 2-4 %) in the fruits packed with sealed PE bag or sealed in PE bags containing ethylene absorbents. The weight loss significantly increased with the increase of the storage temperature. Therefore, lowering the storage temperature would reduce the weight loss. Different packaging methods affected storage life of fruits. Using 5-10o C as example, the fruits of ‘Tainung No.2’ packed in sealed PE bags or sealed PE bags containing ethylene absorbents significantly extended the storage life to 25-26 days compared to unpacked fruits with 21 days of storage life, whereas the ‘Sunrise’ fruits were 22-24 days and 19-21 days, respectively. The fruit qualities in TSS and titratable acidity (TA) were not affected by different packaging methods. Fruits packed in sealed PE bags or sealed in PE bags containing ethylene absorbents retained the vitamin C content and delayed fruit peel yellowing and softening. However, papaya fruits storing at 5oC for 14 days exhibited surface pitting and water soaked symptoms of chilling injury; therefore, papaya fruits were not suitable for storing at 5oC. It is suggested that the papaya fruits should be stored at 10oC during storage and transportation. The respiration and ethylene production rate of ‘Tainung No.2’ fruits subjected to 1-MCP treatment were lower than those of the fruits not subjected to the treatment. The higher the concentration of 1-MCP treatment at 0.1-5.0 ppm, the inhibition of the respiration and ethylene production was more pronounced. Also, the time for the peaks of climacteric respiration and ethylene production was delayed. In addition, the 1-MCP treatment also inhibited the enzyme activities of pectinesterase (PE) and polygalacturonase (PG). The higher the concentration of 1-MCP treatment at 1.0-5.0 ppm, the inhibition of the enzyme activities of PE and PG were pronounced. Even at seven days after 1-MCP treatment, the 1-MCP treated fruit retreated with ethephon (1,000 ppm), the activities of PE and PG were not recovery. The prestorage heat treatment of papaya fruit (‘Tainung No.2’) at 56-60 oC and 8-16 sec. decreased the respiration and ethylene production rate. The days required to reach the climacteric peak of respiration and ethylene also delayed. The flesh firmness of fruits with prestorage heat treatment were significantly higher than those of non-heated fruits. The higher treated temperatures (56-60 oC) and longer duration (8-16 sec.), the higher flesh firmness of fruits. Therefore, the prestorage heat treatment was significantly inhibited the softening of papaya fruits. Prestorage heat treatment did not significantly affect the fruit qualities in terms of TSS, TA, pH, and vitamin C, and the color of the fruit (peel and flesh) in terms of brightness, color saturation and hue angle.

The South African Citrus Industry is the second largest exporter of citrus, after Spain. The industry is under pressure to supply high quality fruit as well as to expand into new, high paying markets. However, high paying markets such as Japan and the USA require cold sterilised fruit as obligatory quarantine treatments against Mediterranean fruit fly (Ceratitis capitata) in order to reduce any possible spread of the pest. Citrus fruit originated from tropical climates and hence are chilling susceptible. Chilling injury symptoms appear as dark brown spots, pitting and/or decay when fruit are transferred to shelf temperatures; thus reducing the marketability of citrus fruit. Therefore, there is need for methods to mitigate chilling injury. Previous studies have shown silicon to mitigate many forms of stress without any hazardous effect on human health. Thus, the aim of the study was to investigate the potential of post-harvest silicon dips in mitigating chilling symptoms in citrus fruit. Briefly, fruit from two sources (Ukulinga Research Farm and Ithala Farm) were dipped in different silicon concentrations (0, 50, 150, and 250 mg ℓ-1) for 30 minutes and thereafter stored at -0.5 or 2⁰C for up to 28 days with weekly evaluation for chilling injury symptoms. Total antioxidants were determined using FRAP, ABTS, and DPPH assays under spectrophotometer. In addition, sugars, ascorbic acid, phenolics and flavonoids were analysed using High Performance Liquid Chromatography (HPLC). Fruit from Ukulinga Research Farm showed significantly higher total antioxidants (ascorbic acid total phenolics and specific flavonoids hesperidin and naringin) and sugars relative to fruit from Ithala Farm. Low concentrations of silicon dips significantly reduced the appearance of chilling injury symptoms by inducing an enzymatic conversion of glucose to ascorbic acid, thereby increasing the antioxidant capacity of chilling susceptible fruit. Moreover, silicon increased the concentration of total antioxidants, total phenolics and total flavonoids. High silicon concentrations had a negative effect on post-harvest quality of lemons by increasing fruit weight loss and electrolyte leakage, resulting in appearance of chilling symptoms. In conclusion, the study showed that silicon had potential to reduce chilling injury. However, high silicon concentrations raised concern, in particularly, on fruit appearance.
Thesis (M.Sc.Agric.)-University of KwaZulu-Natal, Pietermaritzburg, 2012.

碩士
國立屏東科技大學
農園生產系所
102
The series of studies were conducted to elucidate the changes of physico-chemical characteristics during fruit growth and development in five cultivars of bitter gourd (Momordica charantia L.) fruits (cv. ‘Moom Shine’, ‘Luxuriance’, ‘Jadeite’, ‘New Moon’ and ‘Kaohsiung No.1’). Moreover, the influences of different storage temperature and heat treatment for ‘Big Rice’ and ‘Luxuriance’ were investigated. It is possible to find out the optimum storage temperature and method on fruit storage life. The results showed that ‘Kaohsiung No.1’ was fastest during the growth and development of the cultivars. In 5 days after pollination, specific gravity of five cultivars decreased. The color of peel in five cultivars had no significant change in 12 days after pollination. The firmness of ‘New Moon’ and ‘Kaohsiung No.1’ increased, others decreased. Total soluble solid content in 15 days after pollination had a significant change. Vitamin C in five cultivars had a significant change, especially ‘New Moon’ was highest. The color of peel in ‘Big Rice’ and ‘Luxuriance’ had no significant change at different storage temperatures. The chilling injury index of ‘Big Rice’ was the lowest without package during 5℃ storage. The chilling injury index of ‘Luxuriance’ was the lowest with package during 5℃ storage. The chilling injury index occurred earliest in ‘Luxuriance’ than ‘Big Rice’ during 5°C storage. The weight loss of ‘Big Rice’ was 0.76% with package during 5℃ of 20 days’ storage. The weight loss of ‘Luxuriance’ was within 0.94% with package during 0, 5 and 10℃ of 15 days’ storage. The storage life of ‘Big Rice’ and ‘Luxuriance’ had been affected by storage temperature. ‘Big Rice’ and ‘Luxuriance’ were stored at 5℃ with package, the weight loss can be reduced and preserved. The visual freshness of ‘Big Rice’ and ‘Luxuriance’ after 40°C hot water treatment was best, but they after 50°C hot water treatment was worst. The chilling injury index and pitting of ‘Big Rice’ and ‘Luxuriance’ after 40°C hot water treatment was lowest, but they after 50°C hot water treatment was highest. 40℃ hot water treatment had the better effect on reducing chilling injury symptoms, but 50℃ hot water treatment increased chilling injury and non-chilling injury symptoms.

New emerging markets such as Japan and the United States require cold sterilisation of South African citrus fruit as a phytosanitary standard against fruit fly. However, citrus fruit are chilling susceptible, with lemons being the second-most chilling susceptible after grapefruit. Chilling injury is a physiological rind disorder; the occurrence of which is despite its prevalence in horticultural commodities, not well understood. Therefore, the aim of this study was to investigate physiological compounds regulating chilling susceptibility or resistance in citrus fruit, with special emphasis on lemons. Furthermore, the potential of hot water dips or “molybdenum soaks” to maintain a certain level of physiological compounds which determine manifestation of chilling injury symptoms in citrus fruit was investigated. Moreover, it was attempted to create an understanding of the order in which physiological compounds mitigate chilling injury. Lemon fruit from different farms known to be chilling susceptible or resistant were obtained during the 2007 and 2008 harvest season. Thereafter, fruit were treated by soaking for 30 min in 1μM NaMo04.2H20 solution followed by a 2 min HWD 47 or 53°C. Treated fruit were waxed, weighed and stored at -0.5°C for up to 28 days and sampled for chilling injury evaluation 7, 14, 21, or 28 days into cold storage. A second evaluation was carried out five days after withdrawal from cold storage to allow development of chilling injury symptoms as a shelf-life simulation. After the second evaluation fruit were peeled, peel freeze-dried, milled using mortar and pestle and stored at -21°C for further physiological analysis. Freeze-dried peel was analysed for soluble sugars (glucose, fructose, sucrose), vitamin C (ascorbic acid), vitamin E (α-tocopherol), β-carotene, polyamines (putrescine, spermine, spermidine), specific flavanones (naringin and hesperidin) using HPLC-UV-Vis detector and proline, total antioxidant assays (FRAP, ABTS, DPPH), total phenolics, total flavonoids, lipid peroxidation using spectrophotometry, as well as for the heat shock protein (HSP70) using electrophoresis and silver-staining. Chilling susceptibility of lemon fruit varied with fruit source; those sourced from Ukulinga and Eston Estates were chilling resistant, while fruit from Sun Valley Estates showed chilling injury symptoms after 28 days of cold storage plus five days shelf-life. Furthermore, hot water dips (HW) 53°C, 1 μM Molybdenum (Mo) and 10 μM Mo plus HW 53°C significantly reduced chilling injury symptoms compared with the control and HW 47°C. In addition, Sun Valley Estates fruit also showed higher fruit weight loss compared with non-chilling resistant lemons. The alignment of higher fruit weight loss during storage with chilling susceptibility ascertains the use of weight loss as a non-destructive parameter for chilling susceptibility. With respect to flavedo sugars, glucose was found to be the dominant soluble sugar with multi-functional roles during cold storage. This plays a significant role in mitigating cellular stress. Chilling susceptible lemons from Sun Valley Estates had low flavedo glucose concentrations and, therefore, little conversion of glucose to ascorbic acid was possible resulting in a low antioxidant capacity. However, treatments with HW 53°C and Mo soaks seemed to enhance the enzymatic conversion of glucose to ascorbic acid leading to a higher antioxidant capacity in the flavedo of such treated fruit. Furthermore, glucose also feeds into the pentose phosphate pathway which is coupled with the shikimate pathway synthesizing secondary metabolites, especially of the phenolics group. The decrease in glucose was aligned to the levels of total phenolics, but not to that of β-carotene, naringin and hesperidin through 28 days into cold storage period. Moreover, as glucose also feeds into shikimate pathway, simultaneously an increase in proline flavedo concentration was observed. Proline is an antioxidant synthesized from glutamate; as cellular glucose decreases so does the total antioxidant capacity during cold storage. Ascorbic acid is a dominant and potent antioxidant in lemon flavedo as proven with the FRAP, ABTS and DPPH assays. Chilling resistant fruit have significantly higher ascorbic acid conversion. Furthermore, ascorbic acid also acts to generate the α-tocopheroxy radical to further important membrane-bound antioxidant, vitamin E (α-tocopherol equivalent). Furthermore, the DPPH assay was found to be effective in quantifying total antioxidants in lemon flavedo since it detects both lipophilic and hydrophilic antioxidants compared with the ABTS and FRAP assays which are bias to the estimation of liphophilic or hydrophilic antioxidants, respectively. The hot water and molybdenum treatments increased total antioxidants (DPPH assay) with reduced lipid peroxidation 7 days into cold storage and therefore, reduced chilling symptoms in fruit from Sun Valley Estates. The capacity of antioxidant to scavenge reactive oxygen species (ROS) was increased during cold storage and membrane stability significantly improved. Furthermore, putrescine as low valency polyamine was reduced as such compound acted as precursor to the synthesis of the high valency polyamines, spermine and spermidine. Chilling susceptible lemons from Sun Valley Estates showed increased soluble-conjugated polyamines as a response to stress. Furthermore, HW 53°C, 1 μM Mo and 10 μM Mo plus HW 53°C significantly increased the protein concentration and, therefore, likely also the occurrence of proteins with 70kDa (as estimator of HSP70). Additionally, the concentration of conjugated high valency polyamines was also increased, resulting in reduced chilling injury symptoms. The effect of ROS has only been viewed as damaging, while recently their role has also been viewed as stress acclamatory signalling compounds when produced concentrations below critical damaging threshold. Therefore, hot water dips seems to signals synthesis of total protein which include HSPs which then act throughout cold stress to protect other protein and channel other damaged proteins towards proteolysis. While molybdenum increased ROS production below damaging critical threshold, with ROS signalling stress acclimation by further signalling production of bioactive compound with antioxidant properties.
Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2012.