Thesis (D.Phil.(Department of Microbiology and Plant Pathology))-University of Pretoria, 2006. / Includes summary. Includes bibliographical references. Available on the Internet via the World Wide Web.

Lenticels are macroscopic openings occurring on the surface of roots, shoots and some fruits like apples, pears, avocados and mangos and are responsible for gaseous exchange and transpiration. The discolouration of the lenticels of some mango cultivars is a serious problem, affecting the economic value of the fruit, especially in ‘TA’ and ‘Keitt’ while problems with lenticel discolouration are seldom found in ‘Kent’. Mango fruit lenticels develop from ruptured stomata on fruit from about 20 mm in ‘TA’ and ‘Keitt’ and 30 to 40 mm in ‘Kent’. Lenticels enlarge as the fruit grows due to stretching of the fruit surface, reaching their maximum size on adult fruit. Fully developed lenticels of ‘TA’ and ‘Keitt’ are larger in size than those of ‘Kent’. ‘Kent’ lenticels are also better insulated than ‘TA’ and ‘Keitt’, having a thick cuticle in the lenticel cavity and in some instances a phellogen is also present, while both of above mentioned characteristics are absent in ‘TA’ and ‘Keitt’. Resin present in the skin of the fruit plays an important role in the discolouration of ‘TA’ and ‘Keitt’ lenticels. The resin of both ‘TA’ and ‘Keitt’ fruit contain a considerable amount of an aggressive compound termed terpenes. These terpenes are volatile and are able to move out of the resin ducts via the sublenticellular cells to the outside of the fruit through the lenticels. The integrity of tonoplasts of the sublenticellular cells are lost due to the action of the terpenes, causing vacuolar bound phenols to come into contact with polyphenol oxidase present in the cell walls. The product of the resultant reaction is a quinone accumulating as a brownish deposit in the cell walls, visible from the outside as black markings around the lenticels. Lenticel discolouration may, however also occur due to maltreatment or rough handling of fruit, high temperatures in the warm water bath, extended brushing on packline or breaking of the cold chain and spilling of resin onto the surface of the fruit. Copyright 2005, University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria. Please cite as follows: Bezuidenhout, JLJ 2005, Lenticel development and discolouration in the fruit of some mango (mangifera indica L.) cultivars, MSc(Agric) dissertation, University of Pretoria, Pretoria, viewed yymmdd < http://upetd.up.ac.za/thesis/available/etd-03072006-120414 / > / Dissertation (MSc (Agric))--University of Pretoria, 2007. / Plant Production and Soil Science / unrestricted

A presente proposta teve como objetivo avaliar aspectos anatômicos e físico-químicos em frutos de macieiras (Malus domestica Borkh.), Gala e Galaxy, cultivadas em três diferentes altitudes, buscando correlacioná-las ao distúrbio fisiológico, conhecido por lenticelose (lenticel breakdown), caracterizado pelo escurecimento das lenticelas e ocorrência de depressões de coloração parda ao redor destas estruturas. Os frutos maduros foram colhidos na safra 2008-09, em pomares comerciais localizados em cada uma das três áreas produtoras: Vacaria (RS), Fraiburgo (SC) e São Joaquim (SC), localizadas a 971, 1.048 e 1.353 m de altitude, respectivamente. As avaliações foram realizadas nos frutos maduros recém-colhidos e durante o armazenamento, quando os frutos foram submetidos a duas condições distintas: refrigeração (0ºC e 90% UR) e atmosfera controlada (1,5% O2; 2,5% CO2; 0ºC e 90% UR). Os frutos foram avaliados anatomicamente na colheita e durante o armazenamento quando detectado algum distúrbio fisiológico relacionado às lenticelas. A superfície dos frutos maduros de macieiras Gala e Galaxy, recém-coletados nas três localidades e ao final do armazenamento nas condições estudadas, foram analisadas ao microscópio eletrônico de varredura a fim de comparar a deposição das ceras epicuticulares. Adicionalmente os frutos foram avaliados em intervalos de 30 dias, durante os armazenamentos quanto ao teste de tingimento de lenticelas (número) e aos seguintes atributos de qualidade: cor, firmeza, índice de maturação, teor de sólidos solúveis, acidez titulável e, ou outros distúrbios fisiológicos. Também foi analisada a estrutura anatômica dos frutos de macieiras Gala e Galaxy, coletados em Vacaria (RS), em diferentes fases do desenvolvimento a fim de caracterizar a formação dos diferentes tipos de lenticelas. Não houve diferenças no padrão de formação das lenticelas entre Gala e Galaxy e entre os locais de produção. Nos frutos com o sintoma da lenticelose havia uma depressão na superfície resultante da obliteração de células da epiderme e camadas subepidérmicas, sendo que no parênquima subjacente à depressão havia amplos espaços formados pela lise das células. Nem sempre a área sintomática estava associada à presença da lenticela. Os resultados mostraram que a altitude não interferiu na espessura cuticular nem no padrão de deposição de ceras epicuticulares nos frutos de macieiras Gala e Galaxy. Nos frutos recém-colhidos de Gala e Galaxy foi observada a deposição de ceras na forma de plaquetas paralelas e o mecanismo de rompimento e reparo. Após quatro meses de armazenamento, houve alteração no formato das ceras epicuticulares de plaquetas para aglomerados esféricos ou amorfos nos frutos da Gala e Galaxy provenientes de todas as localidades. As alterações foram mais evidentes na condição de armazenamento em atmosfera controlada. Não houve diferenças significativas entre as duas condições de armazenamento e a manifestação dos sintomas nas macieiras Gala e Galaxy procedentes das três regiões produtoras em relação aos parâmetros físico-químicos analisados. A maior incidência ocorreu em frutos Gala provenientes de São Joaquim (SC) ao final do período de armazenamento. / The aim of this study was to describe anatomical and physico-chemical characteristics of apple fruits (Malus domestica Borkh.) \' Gala \' and \' Galaxy \' grown in three different altitudes, seeking to correlate them to the physiological disorder known as lenticelose (lenticel breakdown), characterized by the darkening of lenticels and the occurrence of brownish depressions around them. Mature fruits were harvested in 2008-09, from commercial orchards located in each of three producing areas: Vacaria (RS), Fraiburgo (SC) and São Joaquim (SC), located at 971, 3.088 and 1.353 m altitude, respectively. The evaluations were realized in the mature, freshly harvested fruits and during the storage, when the fruits were subjected to two distinct conditions: refrigeration (0ºC and 90% HU) and controlled atmosphere (1.5% O2; CO2; 2.5%, 0ºC and 90% HU). The fruits were evaluated anatomically at the harvest moment and during storage, when any physiological disorder related to lenticels was detected. The surface of the mature fruit of apple \'Gala \' and \'Galaxy \' freshly harvested from the three localities and at the end of the storage period in the studied conditions were examined under scanning electron microscope to compare the deposition of epicuticular waxes. Additionally, the fruits were evaluated at every 30 days, during storage, in relation to lenticels dyeing test (number) and to the following qualitative attributes: color, firmness, index of ripening, soluble solids content, titratable acidity and physiological disorders. In order to characterize the formation of different types of lenticels, the anatomical structure of fruits, collected in Vacaria (RS), it was also analyzed in different stages of development. There were no differences in the pattern of formation of lenticels between \'Gala\' and \'Galaxy\' and the producing areas. Fruits with \'lenticel breakdown\' symptoms had a surface depression as a result of the obliteration of the epidermal and sub epidermal cells, and the underlying parenchyma exhibited large spaces formed by cell lyses. The symptomatic area was not always associated to the presence of lenticels. The results showed that the altitude did not affect the cuticular thickness or the pattern of deposition of epicuticular waxes in apple fruits of \'Gala\' and \'Galaxy\'. In freshly harvested fruits it was observed the deposition of wax platelets and the mechanism named Tear and Repair or Rip and Stitch\". After four months of storage, we observed changes in the shape of the waxes from platelets to spherical or amorphous clusters in fruits of \'Gala\' and Galaxy from all producing areas. The changes were most evident in controlled atmosphere storage condition. There were no significant differences between the two storage conditions and the onset of symptoms in fruits from the three producing areas in relation to the physico-chemical parameters. The highest incidence of symptoms occurred in fruit \'Gala\' from São Joaquim (SC) at the end of the storage period.

A presente proposta teve como objetivo avaliar aspectos anatômicos e físico-químicos em frutos de macieiras (Malus domestica Borkh.), Gala e Galaxy, cultivadas em três diferentes altitudes, buscando correlacioná-las ao distúrbio fisiológico, conhecido por lenticelose (lenticel breakdown), caracterizado pelo escurecimento das lenticelas e ocorrência de depressões de coloração parda ao redor destas estruturas. Os frutos maduros foram colhidos na safra 2008-09, em pomares comerciais localizados em cada uma das três áreas produtoras: Vacaria (RS), Fraiburgo (SC) e São Joaquim (SC), localizadas a 971, 1.048 e 1.353 m de altitude, respectivamente. As avaliações foram realizadas nos frutos maduros recém-colhidos e durante o armazenamento, quando os frutos foram submetidos a duas condições distintas: refrigeração (0ºC e 90% UR) e atmosfera controlada (1,5% O2; 2,5% CO2; 0ºC e 90% UR). Os frutos foram avaliados anatomicamente na colheita e durante o armazenamento quando detectado algum distúrbio fisiológico relacionado às lenticelas. A superfície dos frutos maduros de macieiras Gala e Galaxy, recém-coletados nas três localidades e ao final do armazenamento nas condições estudadas, foram analisadas ao microscópio eletrônico de varredura a fim de comparar a deposição das ceras epicuticulares. Adicionalmente os frutos foram avaliados em intervalos de 30 dias, durante os armazenamentos quanto ao teste de tingimento de lenticelas (número) e aos seguintes atributos de qualidade: cor, firmeza, índice de maturação, teor de sólidos solúveis, acidez titulável e, ou outros distúrbios fisiológicos. Também foi analisada a estrutura anatômica dos frutos de macieiras Gala e Galaxy, coletados em Vacaria (RS), em diferentes fases do desenvolvimento a fim de caracterizar a formação dos diferentes tipos de lenticelas. Não houve diferenças no padrão de formação das lenticelas entre Gala e Galaxy e entre os locais de produção. Nos frutos com o sintoma da lenticelose havia uma depressão na superfície resultante da obliteração de células da epiderme e camadas subepidérmicas, sendo que no parênquima subjacente à depressão havia amplos espaços formados pela lise das células. Nem sempre a área sintomática estava associada à presença da lenticela. Os resultados mostraram que a altitude não interferiu na espessura cuticular nem no padrão de deposição de ceras epicuticulares nos frutos de macieiras Gala e Galaxy. Nos frutos recém-colhidos de Gala e Galaxy foi observada a deposição de ceras na forma de plaquetas paralelas e o mecanismo de rompimento e reparo. Após quatro meses de armazenamento, houve alteração no formato das ceras epicuticulares de plaquetas para aglomerados esféricos ou amorfos nos frutos da Gala e Galaxy provenientes de todas as localidades. As alterações foram mais evidentes na condição de armazenamento em atmosfera controlada. Não houve diferenças significativas entre as duas condições de armazenamento e a manifestação dos sintomas nas macieiras Gala e Galaxy procedentes das três regiões produtoras em relação aos parâmetros físico-químicos analisados. A maior incidência ocorreu em frutos Gala provenientes de São Joaquim (SC) ao final do período de armazenamento. / The aim of this study was to describe anatomical and physico-chemical characteristics of apple fruits (Malus domestica Borkh.) \' Gala \' and \' Galaxy \' grown in three different altitudes, seeking to correlate them to the physiological disorder known as lenticelose (lenticel breakdown), characterized by the darkening of lenticels and the occurrence of brownish depressions around them. Mature fruits were harvested in 2008-09, from commercial orchards located in each of three producing areas: Vacaria (RS), Fraiburgo (SC) and São Joaquim (SC), located at 971, 3.088 and 1.353 m altitude, respectively. The evaluations were realized in the mature, freshly harvested fruits and during the storage, when the fruits were subjected to two distinct conditions: refrigeration (0ºC and 90% HU) and controlled atmosphere (1.5% O2; CO2; 2.5%, 0ºC and 90% HU). The fruits were evaluated anatomically at the harvest moment and during storage, when any physiological disorder related to lenticels was detected. The surface of the mature fruit of apple \'Gala \' and \'Galaxy \' freshly harvested from the three localities and at the end of the storage period in the studied conditions were examined under scanning electron microscope to compare the deposition of epicuticular waxes. Additionally, the fruits were evaluated at every 30 days, during storage, in relation to lenticels dyeing test (number) and to the following qualitative attributes: color, firmness, index of ripening, soluble solids content, titratable acidity and physiological disorders. In order to characterize the formation of different types of lenticels, the anatomical structure of fruits, collected in Vacaria (RS), it was also analyzed in different stages of development. There were no differences in the pattern of formation of lenticels between \'Gala\' and \'Galaxy\' and the producing areas. Fruits with \'lenticel breakdown\' symptoms had a surface depression as a result of the obliteration of the epidermal and sub epidermal cells, and the underlying parenchyma exhibited large spaces formed by cell lyses. The symptomatic area was not always associated to the presence of lenticels. The results showed that the altitude did not affect the cuticular thickness or the pattern of deposition of epicuticular waxes in apple fruits of \'Gala\' and \'Galaxy\'. In freshly harvested fruits it was observed the deposition of wax platelets and the mechanism named Tear and Repair or Rip and Stitch\". After four months of storage, we observed changes in the shape of the waxes from platelets to spherical or amorphous clusters in fruits of \'Gala\' and Galaxy from all producing areas. The changes were most evident in controlled atmosphere storage condition. There were no significant differences between the two storage conditions and the onset of symptoms in fruits from the three producing areas in relation to the physico-chemical parameters. The highest incidence of symptoms occurred in fruit \'Gala\' from São Joaquim (SC) at the end of the storage period.

Η δομή των φακιδίων μελετήθηκε κατά τη διάρκεια του έτους με τη χρήση ηλεκτρονικού μικροσκοπίου σάρωσης (Scanning Electron Microscopy – SEM), οπτικού μικροσκοπίου, οπτικού μικροσκοπίου φθορισμού καθώς και με ιστοχημικές τεχνικές. Παρατηρήθηκαν διαφορές μεταξύ των σχηματισμών των δύο υπό έρευνα φυτών. Τα φακίδια της Olea europaea (ελιά) ανήκουν στον τύπο Magnolia, Populus και Pyrus (Esau, 1965). Τα γεμιστικά κύτταρα είναι φελλοποιημένα, όπως προκύπτει από τις ιστοχημικά δεδομένα μας και δεν υπάρχει κανενός είδους καλυπτήριο στρώμα (closing layer). Χαλαρά διευθετημένα, με λεπτά τοιχώματα κύτταρα εναλλάσσονται ετησίως με κύτταρα με παχιά τοιχώματα με μικρότερους μεσοκυττάριους χώρους. Καθ’ όλη τη διάρκεια του έτους, ο φθορισμός της χλωροφύλλης παρατηρήθηκε εντονότερος σε περιοχές του φλοιού παρακείμενες στα φακίδια από ότι σε πιο απομακρυσμένες Τα φακίδια του Cercis siliquastrum (κουτσουπιά) ανήκουν στον τύπο Prunus και Robinia (Esau, 1965). Χαρακτηρίζονται από στιβάδες χαλαρά διευθετημένων, μη φελλοποιημένων γεμιστικών κυττάρων τα οποία καλύπτονται από ένα στρώμα φελλοποιημένων κυττάρων (closing layer). Το στρώμα αυτό σπάζει κατά την αρχή της βλαστητικής περιόδου εξαιτίας της πιέσεως που δημιουργείται από τα υποκείμενα, μη φελλοποιημένα κύτταρα, τα οποία συνεχώς παράγονται από το φελλογόνιο κατά την περίοδο αυτή και αντικαθίσταται από ένα νέο στρώμα που δημιουργείται προς το τέλος της. Αντιστοιχίες παρατηρήθηκαν με την Olea europaea όσον αφορά στο φθορισμό της χλωροφύλλης. / The structure of primary lenticels of the Mediterranean evergreen Olea europaea and the winter deciduous species Cercis siliquastrum was investigated during the year using scanning electron, conventional bright field and epi-fluorescence microscopy. It was revealed that lenticels of O.europaea do not undergo significant structural changes during the year. The filling tissue of O.europaea lenticels consists of fully-suberized cells which form small intercellular spaces. The air-exposed filling cells are replaced during spring and early summer by new early-suberized cells; further remarkable structural modifications during the year were not observed. On the contrary, lenticels of C. siliquastrum possess a closing layer of suberized cells delimiting an underlying mass of non-suberized filling cells. During the period of high metabolic activity of the plant, i.e. during spring and early summer the suberized closing layer is broken from the pressure the underlying newly formed cells exercise. During late summer a new closing layer is formed, delimiting again the non-suberized underlying filling cells during winter. The possible role of lenticels in the gas exchange process is discussed. In both species the shade adapted parenchyma cells of the cortex beneath lenticels shows bright chlorophyll red auto-fluorescence, a phenomenon which is not yet fully understood.

As the second most popular fruit world-wide, cultivation of mangoes in South Africa is of strategic economic importance. Competitive export markets require horticultural practices that meet international regulations concerning cultivation, pest control and maintenance of fruit physiology during export. The implementation of such practices, however, cannot be cost effective and successful without detailed and scientific-based knowledge of the commodity concerned. This study of the epicuticular surface of mango fruit has described the ontogeny, morphology and some chemical aspects thereof. Contributions from this study include the following findings: -- Ontogeny and morphology of mango fruit wax: This study found that the highly intricate wax crystalloid structures were not strictly cultivar dependant. A complex series of events constitutes epicuticular wax development. The development of epicuticular crystalloids is accompanied by considerable changes in cutin and epidermal cell morphology. -- Morphology of mango lenticels: An unusual morphology with some cultivar dependent lenticel characteristics was described. Exhaustive past attempts at management of the manifestation of the economically important lenticel discolouration were placed in perspective by establishing the cosmetic nature of the condition. It was found that the density and distribution of epicuticular wax contribute to morphological characteristics of lenticels of individual cultivars. -- Chemical characterisation of mango fruit wax: The chemical complexity of the dual layered epicuticular wax of mango fruit was established by this study, and the validity of interchanging Raman spectroscopy and Fourier transform infrared spectroscopy as investigative techniques established. -- Chemical profiles of discolouring lenticels: The development of lenticel discolouration as a stress-related self-defence mechanism was shown through use of combined chemical and visualisation techniques. This study confirmed the superficial nature and self-defence role of discoloured lenticels. -- Impact of some pre- and postharvest practices on mango fruit wax: Not only postharvest, but also preharvest management of mango fruit must consider the epicuticular membrane as part of the fruit-atmosphere interface. Maintaining a balance between them depends on a better understanding of the interdependence of management and fructosphere dynamics. Both a preharvest and a postharvest practice were studied: ----- Preharvest treatment of mangoes with uncalcined kaolin. Sunburn is an economically important problem in all fruit and vegetable crops. This study has showed that solutions to contain the problem can, however, not be transferred between crops without scientific knowledge of the physiological impacts and long term repercussions thereof. ----- Effect of mechanical handling on the packline and commercial wax coating. Physical and chemical impacts from the packline bring about progressive, irreversible changes to the fruit epicuticular wax. To benefit from these changes, strict management and process control must be practiced. / Thesis (PhD (Plant Pathology))--University of Pretoria, 2007. / Microbiology and Plant Pathology / unrestricted