2,139 research outputs found
Initial events and inter-organ relations during senescence of orchid (Cymbidium) flowers
No full textDuring storage and transportation, harvested crops are continuously exposed to all kinds of stress, such as desiccation and mechanical damage. These conditions are known to shorten shelf life and this is often associated with an earlier appearance of the sudden upsurge in ethylene production. It is doubtful whether this so-called autocatalytic ethylene production, although presumably necessary for the coordination and integration of the senescence process, is the trigger of senescence. Rather, changes in membrane properties or in ethylene sensitivity at an early stage of senescence may be responsible. An increase in the sensitivity to ethylene may, in turn, be an effect of the synthesis of so-called ethylene-sensitivity factors or the disappearance of inhibiting substances (chapter 1).In Cymbidium flowers, as in other orchids, the stigma, style and stamens are united in an organ called the central column. Two pollinia, covered by an antherious tissue called the anther cap, are positioned on top of the central column. Removal of the pollinia and/or the anther cap (emasculation) is known to dramatically advance the senescence process. In nature, emasculation is carried out by insects, while searching for nectar in the flower, or by mice that feed on these apparently tasteful flower parts. As a result of suboptimal conditions during cultivation the anther caps may be abscised spontaneously, while during postharvest life the flowers may lose their anther cap due to handling.Emasculation generally leads in about one day to red coloration of the labellum (lip), a modified petal differing in shape and color from the others. As the early effect of emasculation is very reproducible and easy to assess visibly, the Cymbidium flower was taken as a model system to study the biochemical changes that appear during stress(emasculation)-induced senescence. The purpose of the work described in this thesis, was to determine the factor(s) responsible for the advanced senescence and to analyse the interorgan relations during the senescence process.From the literature it was derived that the negative effects of emasculation may be due to wounding. The disruption of a presumed cytokinin flow from the pollinia and the anther cap to the central column may also be involved. Concerning the communication between the floral parts, the biological precursor of ethylene, 1-aminocyclopropane-1-carboxylic acid (ACC) as well as so-called ethylene-sensitivity factors ( e.g. short-chain, saturated fatty acids) were suggested to be involved.By using a very sensitive laser-driven photoacoustic detection system for ethylene we were able to show the existence of a small peak in ethylene production almost immediately after emasculation (chapters 2 and 3). This small and short-lasting increase in ethylene production appeared well before the visible symptoms ( e.g. coloration of the lip), indicating a causal relationship.Red coloration of the lip as a result of anthocyanin accumulation becomes visible within approximately one day after emasculation. This process is preceded by a pronounced increase in the activity of the key enzyme in phenylpropanoid metabolism, phenylalanine ammonia-lyase (PAL). A similar effect is apparent after treatment of the flower or the isolated lip with ethylene and inhibitors of ethylene synthesis and ethylene action greatly inhibit coloration. It is therefore concluded that lip coloration is regulated by ethylene (chapters 4 and 5).Desiccation of the rostellum, an anther-derived tissue that is uncovered by emasculation, was found to be the primary factor in emasculation-induced ethylene production (chapter 6). Desiccation leads, possibly through the release of "endogenous elicitors", to an increase in the levels of ACC and malonyl-ACC in the top of the central column, which means that the endogenous elicitor locally stimulated the ACC-synthase activity (chapter 7). Determination of the ethylene production in different flower parts isolated at different times after emasculation, revealed that only the production of the central column shows a significant increase. The other flower parts, including the lip, have only very low productions (chapter 8).Following emasculation, the lip does not show an increase in ethylene production but does show an ethylene effect (coloration). It may therefore be concluded that the sensitivity to ethylene has increased. Similar arguments were used by other authors to introduce a role for unknown sensitivity factors in senescence of Petunia and carnation flowers.However, in vivo measurement of the ethylene production in the central column and the remaining portion of the flower showed that the major part of the ethylene (ca. 80%) is produced by the remaining portion and only a small amount by the central column i.e. at the site of ACC synthesis. In this way it was shown that ACC is rapidly translocated within the flower and that measurements in isolated flower parts do not yield valuable information concerning the in vivo ethylene production (chapter 8). The same is true for the translocation of ACC. Although ACC is rapidly translocated from the central column to the perianth, it is largely immobile in isolated columns (chapter 9). With ACC as a transported intermediate, localized stress affects the senescence processes in all the flower parts. Ethylene Itself was also found to be translocated within the flower and an additional role in the coordination of the senescence process is suggested (chapter 8). No indications for the existence of (mobile) ethylene-sensitivity factors were found and also no biological activity of the wilting and ethylene-sensitivity factors mentioned in the literature was apparent in this system (chapter 9).The emasculation-induced ethylene production has a significant effect on the internal ethylene concentration in all the floral parts. As a result, an increase in the activity of different senescence-related enzymes, e.g. PAL and the ethylene forming enzyme (EFE), was observed (chapter 7). In addition, emasculation leads to an increase in membrane permeability (chapter 3). Although the ethylene production and the internal concentration both decrease to the initial level within one day, the EFE-activity is maintained at a high level for a longer period of time. This higher EFE-activity may stimulate, through negative feedback control rather than by its ethylene production, the ACC-synthase activity, leading to an earlier appearance of the more pronounced upsurge in ethylene production that accompanies senescence (chapter 10)
Residuen op groenten en fruit ter discussie
No full textDe nVWA en het RIVM doen al jaren onderzoek naar residuen van giftige stoffen op groenten en fruit. Uit onderzoek blijkt dat met name peuters en baby’s meer groenten en fruit binnenkrijgen dan eerder werd gedacht. Met meer groenten en fruit zouden ze ook meer residuen binnenkrijgen. Ernst Woltering van Wageningen Universiteit plaatst het één en ander in perspectief
Ethylene production of Botrytis cinerea in vitro and during in planta infection of tomato fruits
No full textContains fulltext :
34799.pdf (Publisher’s version ) (Open Access)Symposium on the Plant Hormone Ethylene, 18 juni 200
Caspase inhibitors affect the kinetics and dimensions of tracheary elements in xylogenic Zinnia (<it>Zinnia elegans</it>) cell cultures
No full textAbstract Background The xylem vascular system is composed of fused dead, hollow cells called tracheary elements (TEs) that originate through trans-differentiation of root and shoot cambium cells. TEs undergo autolysis as they differentiate and mature. The final stage of the formation of TEs in plants is the death of the involved cells, a process showing some similarities to programmed cell death (PCD) in animal systems. Plant proteases with functional similarity to proteases involved in mammalian apoptotic cell death (caspases) are suggested as an integral part of the core mechanism of most PCD responses in plants, but participation of plant caspase-like proteases in TE PCD has not yet been documented. Results Confocal microscopic images revealed the consecutive stages of TE formation in Zinnia cells during trans-differentiation. Application of the caspase inhibitors Z-Asp-CH2-DCB, Ac-YVAD-CMK and Ac-DEVD-CHO affected the kinetics of formation and the dimensions of the TEs resulting in a significant delay of TE formation, production of larger TEs and in elimination of the 'two-wave' pattern of TE production. DNA breakdown and appearance of TUNEL-positive nuclei was observed in xylogenic cultures and this was suppressed in the presence of caspase inhibitors. Conclusions To the best of our knowledge this is the first report showing that caspase inhibitors can modulate the process of trans-differentiation in Zinnia xylogenic cell cultures. As caspase inhibitors are closely associated with cell death inhibition in a variety of plant systems, this suggests that the altered TE formation results from suppression of PCD. The findings presented here are a first step towards the use of appropriate PCD signalling modulators or related molecular genetic strategies to improve the hydraulic properties of xylem vessels in favour of the quality and shelf life of plants or plant parts.</p
Investigation on the cause of tomato fruit discoloration and damage under chilling condition using external antioxidants and hot water treatment
No full textThe color of tomato fruit turns to red from green during ripening. The accumulated lycopene content of red tomato fruits is reduced when the fruits stored in the refrigerator. Therefore, this study was conducted in order to investigate the reason why red color tomato turns to light red when the fruit is stored at chilling temperature. A tomato variety (cv Rotarno) grown under greenhouse condition and harvested at red stage was used to assess color and firmness. Before storage at these temperatures, red tomato fruits were infiltrated by different concentration of antioxidants (Vitamin C, L-galactonic acid-¿-lactone and Butylated hydroxyanisole (BHA) and also treated by hot water. The color and firmness of the fruits were measured by pigment analyzer and Zwick, respectively. Dessicator with vacuum pump was used for infiltration of antioxidants and water. Antioxidants were infiltrated through the scar of the fruits by applying 400 Mbar pressure for 15 sec. for each concentration. Red tomatoes were treated in hot water at 40, 45 and 50°C for 2, 5 and 10 min each. All antioxidant infiltrated and hot water treated fruits were stored at 4°C for three weeks. Statistically significant difference was not observed on color and firmness among different fruits treated by different concentration of antioxidants. Hot water treatment also showed no significant difference on color value between treated and non-treated fruits. However, hot water treated fruits scored significantly higher firmness than non-treated fruits. In general, the results showed that antioxidants as well as hot water treatment did not maintain accumulated lycopene content of the red tomato fruits which, stored at chilling temperature
Effect of Ethylene and 1-Methylcyclopropene (1-MCP) on color and Firmness of Red and Breaker Stage Tomato Stored at Different Temperatures
No full textThe red color of the tomato fruit during ripening is due to the presence lycopene, a compound known for its antioxidant property. This compound is influenced by temperature, ethylene and 1-Methylcyclopropene (1-MCP) treatment. It was believed that ethylene application at chilling temperature could help increase the amount of lycopene content of tomato fruits. In addition, application of 1-MCP was assumed to reduce the action of ethylene on production of lycopene content and decrease loss of firmness of tomato fruit under chilling temperature. Therefore, the objective of this experiment was to see the effect of ethylene and 1-MCP treatment on color and firmness of tomato fruit under different storage temperatures. A tomato variety (cv. Rotarno) grown under greenhouse condition harvested at red and breaker stage was stored at 4, 8 and 20°C to assess color and firmness. Tomato fruits were treated by ethylene (85.7 ppm) and 1-MCP (2.9 ppm) gases starting from the first day of storage throughout the experimentation period. The color and firmness of the fruits were measured by pigment analyzer and Zwick respectively. Results showed that there was significant difference in color value of ethylene treated breaker stage tomato. 1-MCP treatment reduced the color value of tomato fruits stored at 20°C more than the fruits stored at 4 and 8°C. However, 1-MCP treatment helped to reduce loss of firmness of the fruits. We conclude that external ethylene application on red tomato fruits stored at chilling temperature generally has no effect on the subsequent accumulation of lycopene or to maintain the loss of accumulated lycopene during chilling storage. However, external ethylene treatment on breaker stage tomatoes helps for red color development. In addition, 1-MCP treatment helps to reduce loss of firmness of the fruits
Effect of home-refrigerator storage temperature on tomato quality
No full textPostharvest storage, handling and distribution of fruit at low temperatures is the most common and manageable approach to control ripening and subsequent deterioration and to maximize product shelf-life. However, tomatoes, as many other subtropical fruits, are susceptible to develop symptoms of chilling injury, a physiological disorder caused by the exposure to low temperature above the freezing point. Development of chilling injury depends on temperature, time, ripening stage and tomato type/cultivar. We studied the effect of home-refrigerator storage temperature on the quality of two types of tomato: cocktail tomato (cultivars ‘Amoroso’ and ‘Brioso’) and truss tomato (cultivars ‘Capricia’ and ‘Roterno’). Fully ripe tomatoes were stored for 10 days at two temperatures: 4°C as simulation of home-refrigerator storage and 15°C as an optimal storage temperature. We evaluated several quality parameters: weight loss, firmness, soluble solid content, titratable acidity, carbohydrates, titratable acidity and citrate content. Although we did not observe any apparent symptom of chilling injury, we found that 4°C temperature stimulates firmness decay in both cocktail tomato cultivars, increasing fruit susceptibility to mechanical injury. Moreover, already after 5 days of 4°C storage, tomatoes generally showed decreased sugar and increased acid content (especially in cocktail tomatoes) compared to 15°C stored fruit, indicating a loss of sensoric quality at 4°C
Conceptual Design Automation: Abstraction complexity reduction by feasilisation and knowledge engineering
No full textIn order to keep innovating, engineers are working more and more with engineering software, providing them a way to cut away their routine and repetitive activities. Computer aided design and simulation software are for instance considered standard tools in most engineering companies. Today, to solve complex engineering design problems, multidisciplinary design optimisation (MDO) is increasingly used to automate the design process to support the engineer in finding a solution faster. To effectively use MDO, design frameworks such as the design and engineering engine (DEE) are required. More and more does engineering software provide a seamless integration of computer software and human knowledge, a focus point of the field of knowledge engineering (KE). This will free engineers from repetitive and routine tasks and allow them to use their full creative capacity and learn faster, increasing their productivity. This work contributes to the development of KE applications within the DEE to support the MDO process. The focus is on the conceptual design phase of complex systems engineering, responsible for providing an initial start vector for MDO. Aircraft design is taken as a guiding example as it is a typical case of a complex system.Design of Aircraft and RotorcraftAerospace Engineerin
Flower Senescence
No full textCurrent knowledge indicates that flower petal senescence is a form of programmed cell death called vacuolar cell death. In this process the cell first degrades most of the cytoplasm and organelles using an array of degradative enzymes present in the vacuole for reuse of the nutrients. The final step in this process is disruption of the vacuolar membrane by which the hydrolytic enzymes are released to 'finish' what is left of the cell. In ethylene-sensitive flowers, ethylene triggers the cell death process, and flower life can be greatly extended by blocking production or perception of ethylene. This has led to development of very effective chemical treatments with broad application and molecular genetic strategies of potential commercial value. In ethylene-insensitive flowers, the senescence program may be similar to that of ethylene-induced senescence. However, the hormonal or developmental events that trigger the cell death processes in ethylene-insensitive species have not been identified. Many genes and transcriptional regulators with putative roles in senescence have been identified using transcriptomic approaches. Testing their functions in transgenic plants is necessary to design new concepts and treatments for prolonging the life of flowers
Low temperature-induced lycopene degradaton in red ripe tomato evaluated by remittance spectroscopy
No full textTomatoes are mostly harvested at the orange and red-ripe stages. A survey among consumers indicated that tomatoes are most often stored in the refrigerator well below 10 °C, a temperature considered harmful for chilling sensitive products such as tomato. Also during distribution, tomatoes may be exposed to chilling temperatures. The effects of storage at chilling temperatures on quality aspects of tomatoes were investigated. The colour and lycopene content of red ripe tomatoes of two cultivars (cocktail and round type) was evaluated during 20 days of storage at 4, 8, 12 and 16 °C. Colour was repeatedly measured over time by tristimulus colour measurements, RGB image analysis and colour intensity was scored by eye using a consumer panel. Lycopene content was repeatedly assessed by following the NAI index over time. This index, obtained from remittance VIS spectroscopy, was found to relate closely to the lycopene level as measured by HPLC measurements of pericarp tissue. Temperatures below 12 °C resulted in lycopene loss in ripe-red tomatoes and substantial colour loss well assessed by visual evaluation. Colour measurement using tristimulus colour measurements and RGB image analysis did not correlate well with lycopene content. Prior hot water treatment did not prevent lycopene loss. Results show that storage of red ripe tomatoes at chilling temperatures reduces the nutritional and presumed health promoting value and affects fruit visual quality
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