Storage of potatoes : effects of ethylene and 1-MCP on potato tuber quality and biochemistry

Potatoes are widely consumed in UK and many other countries. There is a continuous demand for potatoes all year around both from consumers and retailers such that several postharvest technologies are being used to meet this demand. Sprouting is the main phenomenon affecting both the quality and marketability of potatoes during long term storage. Several sprout suppressants are widely used (e.g. maleic hydrazide and chloropropham, but there are concerns over their toxicity such that alternatives have been sought. Continuous exposure of potato tubers to ethylene (usually 10 µL L- 1 ) during storage was approved by the Chemicals Regulation Directorate since 2003. Even though potatoes have been regarded as non climacteric, this study aimed to examine the effect of different ethylene regimes in combination with or without 1-methylcyclopropene on physiological, biochemical and mechanical characteristics of a selection of important UK cultivars. In 2008-2009, ten potato cultivars were examined for their response to four different ethylene regimes during storage. Storage time and ethylene treatments had a cultivar specific effect on all the measured parameters (sprouting, sugars, texture). Ethylene applied after first indication of sprouting was as effective at sprout inhibition as when applied continuously for certain potato cultivars; therefore this could be considered as a more environmentally and economical alternative for sprouting inhibition. In addition, sugar accumulation was retarded when tubers were subjected to ethylene at the first indication of sprouting compared to those treated with continuous ethylene. In 2009-2010, four potato cultivars were studied and the effect of 1-MCP either before or after ethylene treatment on sprouting, respiration rate, endogenous ethylene production and texture was investigated. 1-MCP is believed to interact with ethylene receptors and therefore prevent or retard ethylene dependent responses. 1-MCP seemed to effectively block ethylene binding sites when applied before storage of tubers in ethylene resulting in less tuber sugar accumulation. In 2010- 2011, the effect and timings of 1-MCP and ethylene treatments on sprouting, tuber respiration, endogenous ethylene production and sugars on two potato cultivars was studied. 1-MCP effectively suppressed the action of ethylene in terms of the increase in the respiration rate or ethylene production and sugar accumulation. Selected potato samples were also analysed quantitavely for an array of phytohormone using a newly developed UPLC QToF MS method. This method had the advantage of quantifying simultaneously a significant number of plant growth regulators that are present in potato (ABA and its metabolites, cytokinins and gibberellins)

Influence of 1-Methylcyclopropene on the biochemical response and ripening of ‘solo' papayas

The market demand for tropical fruits has been growing steadily over the past two decades and global papaya production has grown significantly over the last few years. This sector, however, suffers greatly from postharvest losses due to reduced quantity and quality of fruits between harvest and consumption. The use of ethylene inhibitors after harvest could improve the final quality of the fruit to satisfy the consumer and also minimize waste. The physiological and biochemical responses of ‘Solo’ papayas treated with the ethylene inhibitor 1-methylcyclopropene (1-MCP) to extend storage shelf life and maintain quality during long-term storage are deeply discussed in this study. Papaya fruits arrived at Cranfield University (CU) and received a 24 h 1-MCP, being stored at 20 ºC for 10 days. The ethylene inhibitor 1-MCP application significantly delayed ‘Solo’ papaya ripeness on fruit storage by reducing respiration rate and ethylene production. There was a delay from 7 days in fruit firmness loss and the retention of green peel colour was increased. Inhibition of ethylene perception by 1-MCP did not prevent the accumulation of sugars and the mean values were similar and higher than those found for control fruits, which are possibly due to the lower reaction speed, leading to a higher accumulation

Effect of methyl jasmonate and sucrose on endogenous non-structural carbohydrates in petals and leaves of cut ‘First Red’ roses (Rosa hybrida L.)

Effects of exogenously applied methyl jasmonate (MeJA) and sucrose on vase life and non-structural carbohydrate concentration in petals and leaves of cut ‘First Red’ roses were investigated. Roses were placed in sealed plastic containers and received MeJA vapour treatment (0.1 μL MeJA L-1) for 24 h at 20°C. Flowers were then placed in individual bottles containing 0 or 2% (v/v) sucrose solution. Flower petals and the two uppermost five-leaflet leaves were detached on days 0, d 5 and d 10 of vase life. Samples were individually snap-frozen in liquid nitrogen and freeze-dried. Non-structural carbohydrates were extracted and quantified using standard HPLC coupled to evaporative light scattering detection. The MeJA vapour treatment enhanced vase life of flower and foliage of ‘First Red’ roses. Significant differences were observed between foliage life of cut ‘First Red’ roses that were treated with MeJA and sucrose, but not for flower life. Rose stems treated with MeJA in the absence of sucrose had an extended vase life compared to roses treated with 2% sucrose alone (14.0 vs. 12.8 days of vase life). Sucrose and myo-inositol, and to a lesser extent glucose concentrations in petals of cut roses decreased during vase life, even when flowers were supplied with 2% sucrose. Concomitant to this, fructose levels in petals increased during vase life. Neither sucrose nor MeJA had a significant effect on any of the sugars measured in petals of cut roses. In contrast, significant differences were apparent for all sugars measured in leaves that were treated with MeJA and sucrose solutions. The combination of MeJA and 2% sucrose solution sharply increased endogenous sucrose concentration in leaves, but the opposite was shown in the absence of 2% sucrose. Sucrose treatment alone did not consistently alter endogenous sucrose concentration. Interactions between MeJA and sucrose on sugar metabolism are discussed

Αποθήκευση πατάτας: Επίδραση του αιθυλενίου και του 1-mcp στην ποιότητα και τη βιοχημεία της πατάτας

Potatoes are widely consumed in UK and many other countries. There is a continuous demand for potatoes all year around both from consumers and retailers such that several postharvest technologies are being used to meet this demand. Sprouting is the main phenomenon affecting both the quality and marketability of potatoes during long term storage. Several sprout suppressants are widely used (e.g. maleic hydrazide and chloropropham, but there are concerns over their toxicity such that alternatives have been sought. Continuous exposure of potato tubers to ethylene (usually 10 μL L-1) during storage was approved by the Chemicals Regulation Directorate since 2003. Even though potatoes have been regarded as non climacteric, this study aimed to examine the effect of different ethylene regimes in combination with or without 1-methylcyclopropene on physiological, biochemical and mechanical characteristics of a selection of important UK cultivars. In 2008-2009, ten potato cultivars were examined for their response to four different ethylene regimes during storage. Storage time and ethylene treatments had a cultivar specific effect on all the measured parameters (sprouting, sugars, texture). Ethylene applied after first indication of sprouting was as effective at sprout inhibition as when applied continuously for certain potato cultivars; therefore this could be considered as a more environmentally and economical alternative for sprouting inhibition. In addition, sugar accumulation was retarded whentubers were subjected to ethylene at the first indication of sprouting compared to those treated with continuous ethylene. In 2009-2010, four potato cultivars were studied and the effect of 1-MCP either before or after ethylene treatment on sprouting, respiration rate, endogenous ethylene production and texture was investigated. 1-MCP is believed to interact with ethylene receptors and therefore prevent or retard ethylene dependent responses. 1-MCP seemed to effectively block ethylene binding sites when applied before storage of tubers in ethylene resulting in less tuber sugar accumulation. In 2010- 2011, the effect and timings of 1-MCP and ethylene treatments on sprouting, tuber respiration, endogenous ethylene production and sugars on two potato cultivars was studied. 1-MCP effectively suppressed the action of ethylene in terms of the increase inthe respiration rate or ethylene production and sugar accumulation. Selected potato samples were also analysed quantitavely for an array of phytohormone using a newly developed UPLC QToF MS method. This method had the advantage of quantifying simultaneously a significant number of plant growth regulators that are present in potato (ABA and its metabolites, cytokinins and gibberellins).Οι πατάτες καταναλώνονται ευρέως στο Ηνωμένο Βασίλειο και σε πολλές άλλες χώρες. Υπάρχει μια συνεχής ζήτηση για πατάτες καθ' όλη τη διάρκεια του έτους τόσο από τους καταναλωτές όσο και από τους λιανοπωλητές, έτσι ώστε αρκετές μετασυλλεκτικές τεχνολογίες να χρησιμοποιούνται για την κάλυψη αυτής της ζήτησης. Η φύτρωση είναι το κύριο φαινόμενο που επηρεάζει τόσο την ποιότητα όσο και την εμπορευσιμότητα των πατατών κατά τη διάρκεια της μακροχρόνιας αποθήκευση. Χρησιμοποιούνται ευρέως διάφορα μέσα καταστολής της βλάστησης (π.χ. maleic hydrazide και χλωροπροφάμη), αλλά υπάρχουν ανησυχίες σχετικά με την τοξικότητά τους, με αποτέλεσμα να υπάρχουν εναλλακτικές λύσεις. αναζητήθηκαν εναλλακτικές λύσεις. Συνεχής έκθεση των κονδύλων πατάτας σε αιθυλένιο (συνήθως 10 μL L-1) κατά τη διάρκεια της αποθήκευσης εγκρίθηκε από τη Διεύθυνση Ρύθμισης Χημικών Προϊόντων από το 2003. Ακόμη και το αν και οι πατάτες έχουν θεωρηθεί ως μη κλιμακτηριακές, η παρούσα μελέτη είχε ως στόχο να εξετάσει την επίδραση διαφορετικών καθεστώτων αιθυλενίου σε συνδυασμό με ή χωρίς 1-μεθυλοκυκλοπροπένιο στα φυσιολογικά, βιοχημικά και μηχανικά χαρακτηριστικά των μιας επιλογής σημαντικών ποικιλιών του Ηνωμένου Βασιλείου. Το 2008-2009, εξετάστηκαν δέκα ποικιλίες πατάτας ως προς την ανταπόκρισή τους σε τέσσερα διαφορετικά καθεστώτα αιθυλενίου κατά την αποθήκευση. Χρόνος αποθήκευσης και οι επεξεργασίες αιθυλενίου είχαν επίδραση ειδικά για την ποικιλία σε όλες τις μετρούμενες παραμέτρους (βλάστηση, σάκχαρα, υφή). Το αιθυλένιο που εφαρμόστηκε μετά την πρώτη ένδειξη βλαστήσεως ήταν ως εξής αποτελεσματική στην αναστολή της βλάστησης όσο και όταν εφαρμόζεται συνεχώς για ορισμένες ποικιλίες πατάτας. Επομένως, αυτό θα μπορούσε να θεωρηθεί ως μια πιο περιβαλλοντική και οικονομική λύση και εναλλακτική λύση για την αναστολή της βλάστησης. Επιπλέον, η συσσώρευση σακχάρων επιβραδύνθηκε όταν οι κόνδυλοι υποβλήθηκαν σε αιθυλένιο κατά την πρώτη ένδειξη της βλαστήσεως σε σύγκριση με εκείνους που αντιμετωπίστηκαν με συνεχές αιθυλένιο. Το 2009-2010, μελετήθηκαν τέσσερις ποικιλίες πατάτας και η επίδραση της 1-MCP είτε πριν είτε μετά τη θεραπεία με αιθυλένιο στη βλάστηση, την αναπνοή ρυθμό, την ενδογενή παραγωγή αιθυλενίου και την υφή. Η 1-MCP πιστεύεται ότι αλληλεπιδρά με τους υποδοχείς αιθυλενίου και επομένως εμποδίζει ή καθυστερεί την εξαρτώμενη από το αιθυλένιο αντιδράσεις. Η 1-MCP φάνηκε να μπλοκάρει αποτελεσματικά τις θέσεις δέσμευσης του αιθυλενίου όταν εφαρμόστηκε πριν από την αποθήκευση των κονδύλων σε αιθυλένιο, με αποτέλεσμα λιγότερη συσσώρευση σακχάρων στους κονδύλους. Το 2010-2011, η επίδραση και οι χρονικές στιγμές των επεμβάσεων με 1-MCP και αιθυλένιο στην εκβλάστηση, στους κονδύλους αναπνοή, την ενδογενή παραγωγή αιθυλενίου και τα σάκχαρα σε δύο ποικιλίες πατάτας. μελετήθηκε. Η 1-MCP κατέστειλε αποτελεσματικά τη δράση του αιθυλενίου όσον αφορά την αύξηση της του ρυθμού αναπνοής ή της παραγωγής αιθυλενίου και της συσσώρευσης σακχάρων. Επιλεγμένες πατάτες δείγματα αναλύθηκαν επίσης ποσοτικά για μια σειρά φυτοορμονών με τη χρήση μιας νέας μεθόδου, της UPLC QToF MS. Η μέθοδος αυτή είχε το πλεονέκτημα του ποσοτικού προσδιορισμού ταυτόχρονα έναν σημαντικό αριθμό ρυθμιστών της ανάπτυξης των φυτών που υπάρχουν στην πατάτα (ABA και οι μεταβολίτες του, κυτοκινίνες και γιββερελλίνες)

Σύνθεση Φθορίζοντων δεικτών με δυνατότητα Συναρμογής Ενδοκυτταρίων ιόντων

In this thesis, the synthesis of a fluorescent indicator and its properties aredescribed. MBTC has been synthesized in 13 steps. According to spectrocopic data, it does not coordinate with magnesium,but it is sensitive to cadmium and zinc, with kd Cd+2 = 1.0μM and kdZn+2=1.9μΜ. As a result, it would be used as a zinc fluorescent indicator, like TSQ

Eluorescent and Caged ion probes. Design and Synthetic approaches

Στη διατριβή αυτή περιγράφεται ο σχεδιασμός και η συνθετική μεθοδολογία, η οποία επιλέχθηκε για την παρασκευή φθοριζόντων και φωτομεταβαλλόμενων δεικτών ενδοκυττάριων ιόντων. Οι ενώσεις αυτές σχεδιάστηκαν λαμβάνοντας υπόψη παράγοντες όπως η συγγένεια του δείκτη με το ιόν, η εκλεκτικότητά του σε σχέση με άλλα ιόντα, καθώς και η βελτιστοποίηση των οπτικών τους ιδιοτήτων. Η διατριβή διαιρείται σε τρεις θεματικούς κύκλους : Ο πρώτος περιλαμβάνει το σχεδιασμό και τη σύνθεση τεσσάρων φθοριζόντων τετρακαρβοξυλικών δεικτών ιόντων ασβεστίου. Οι ενώσεις αυτές μπορούν να θεωρηθούν ως ανάλογα της γνωστής χηλικής ένωσης BAPTA. Ο δεύτερος περιλαμβάνει το σχεδιασμό και τις συνθετικές προσπάθειες που έγιναν για τη σύνθεση φθοριζόντων και φωτομεταβαλλόμενων δεικτών ιόντων ασβεστίου. Οι συνθετικές πορείες που ακολούθησαν στηρίχθηκαν σε εκτεταμένη ρετροσυνθετική ανάλυση. Ο τρίτος κύκλος περιλαμβάνει τη σύνθεση τρικαρβοξυλικών δεικτών ιόντων, που είναι δυνατό να θεωρηθούν ως ανάλογα της χηλικής ένωσης APTRA. Επιπλέον παρουσιάζονται οι προκαταρκτικές μετρήσεις των οπτικών ιδιοτήτων των παραπάνω δεικτών.In this thesis the preparation of four tetracarboxilic fluorescent calcium probes of BAPTA-type and the preparation of two tricarboxylic fluorescent ion probes, of APTRA-type is described. These syntheses are the result of extensive retrosynthetic analysis which took in consideration factors such as the affinity of the probes to the target ions, selectivity to the desired ion, optimization of optical properties of the probes as well as the possibility of cell permeability. Morover an extensive retrosynthetic analysis as well as a number of synthetic pathways aiming to the preparation of calcium caged compounds is presented. The thesis also includes preliminary studies of the fluorescent properties of the ion probes in the context of their use as potential intracellular ion probes

Optical coherence tomography imaging of potato skin to understand variability in response to pre- and postharvest factors

In order to be able to assess the effect of pre- and postharvest treatments on different potato cultivars and tissues, information is needed on the skin architecture of tubers. Optical coherence tomography (OCT) was utilised as an appropriate non-destructive technique due to its high spatial resolution. It uses near-infra-red optical radiation to map the internal structures of semi-transparent samples. Samples in this study were potatoes with known provenance, under selected pre- or postharvest treatment. The study herein aimed to examine the effect of the growing environment and a desiccant chemical on skin layer development of several potato cultivars and to increase understanding of the variability in skin thickness after application of sprout suppressant. Different thicknesses of the skin layer were found between different farming locations, cultivars and spatial positions on individual tubers (60 to 100 µm). In detail, the spatial difference of skin layer thicknesses developed over time. Duration of the desiccation and curing did not cause significant differences in the skin thickness. However, skin thickness changes were observed during storage and were cultivar dependent. The chlorpropham treatment did not significantly influence the skin layer thickness. Still images recorded by means of OCT were a convenient and non-destructive tool to quantitatively evaluate the skin thickness of potatoes. In conclusion, the high resolution of the acquired still images allowed confirmation of tissue identification. It appears that the tissue position on the tuber may have a higher influence on the phellem thickness than the harvest date or curing

Uniformity study in PM-HEMT structures and devices by optical and electrical characterization

We have studied the uniformity of both the structure and of the device characteristics of PM-HEMTs on (001) GaAs substrates. The structure uniformity was studied by photoreflectance modulation spectroscopy (PR) at room temperature and photoluminescence spectroscopy (PL) at low temperature. PR was chosen for its main advantages of high sensitivity in room temperature, higher than that of high temperature photoluminescence and non-destructiveness. We have studied the main transitions of the transistor structures using the 2DEG approximation. PR and PL results yield uniformity with relative standard deviation (r.s.d.) lower than 1%. After PR, transistors were fabricated on the wafers and tested for DC and RF characteristics and the results were correlated with the PR data. The comparison between PR and PL has resulted in a strong indication that PR can be the technique of choice for the complete characterization of structure uniformity of 3 inch pseudomorphic heterostructures, since it is non-destructive, relatively simple and can be performed at room temperature. © 1998 Elsevier Science B.V. All rights reserved

Uniformity study in PM-HEMT structures and devices by optical and electrical characterization

We have studied the uniformity of both the structure and of the device characteristics of PM-HEMTs on (001) GaAs substrates. The structure uniformity was studied by photoreflectance modulation spectroscopy (PR) at room temperature and photoluminescence spectroscopy (PL) at low temperature. PR was chosen for its main advantages of high sensitivity in room temperature, higher than that of high temperature photoluminescence and non-destructiveness. We have studied the main transitions of the transistor structures using the 2DEG approximation. PR and PL results yield uniformity with relative standard deviation (r.s.d.) lower than 1%. After PR, transistors were fabricated on the wafers and tested for DC and RF characteristics and the results were correlated with the PR data. The comparison between PR and PL has resulted in a strong indication that PR can be the technique of choice for the complete characterization of structure uniformity of 3 inch pseudomorphic heterostructures, since it is non-destructive, relatively simple and can be performed at room temperature. © 1998 Elsevier Science B.V. All rights reserved