Thesis (Ph. D.)--University of Chicago, 1920. / "Private edition, distributed by the University of Chicago libraries, Chicago, Illinois." "Contributions from the Hull botanical laboratory 280." "Reprinted from the Botanical gazette, vol. LXXI, no. 5, May 1921." "Literature cited": p. 357. Also available on the Internet.

Thesis (MScAgric)--Stellenbosch University, 2002. / ENGLISH ABSTRACT: Internal breakdown (internal browning - IB and gel breakdown - GB), over maturity and immaturity are the main factors adversely affecting the quality of exported South African plums. Maturity problems occur when plums are strip harvested, i.e., all the fruit in a block or orchard are harvested once, when the majority of the fruit are at optimum maturity. This results in both ovennature and immature fruit being harvested and contributes to a high percentage of fruit being rejected for export. In general, internal browning occurs when plums are exported under a single 10\,,, temperature regime and gel breakdown occurs when plums are exported under a dual temperature regime. However, GB can also occur at harvest in fruit that are very ripe and may occur at single low temperatures, where it would be masked by lB. While it is known that some cultivars, like 'Angeleno', can withstand a single temperature regime, others cannot. To the best of our knowledge, the reason for this difference is not understood. Many factors affect the quality of plums, including light incidence in the canopy, mineral nutrition and harvest maturity. Plums that were grown on high density training systems such as 'a V- or spindle system yielded consistently high quality fruit with low incidences of gel breakdown. This was in contrast to earlier findings where low-density training systems produced high levels of GB, especially in the lower part of the tree canopy. Branches that were shaded with 80% shade netting yielded fruit with high levels of GB, indicating that the main effect of improved canopy structure on quality was improved light management. A postharvest boron application on 'Songold' plums prior to storage had no effect on the incidence of intemal breakdown in the fruit, but did damage the cuticle, resulting in severe shrivel. However, internal conductivity and firmness measurements indicated that there was some effect of the boron on cell membranes. A more thorough investigation of pre- and postharvest application of boron is recommended in order to determine whether there could be a positive effect of boron in improving fruit quality in plums. Four cultivars of plums ('Pioneer', 'Sapphire', "Songold ' and 'Angeleno') were harvested throughout, and extending beyond, the commercial harvesting period. In all cultivars, the drop in firmness between harvests was not as great as expected and the later harvested fruit were of a similar, if not superior, quality as compared to the earlier harvested fruit. Later harvested plums tended to have higher TSS and better colour development. Contrary to what was expected, later harvested fruit did not have more internal disorders than earlier harvested fruit. This indicates the importance of harvesting at optimum maturity. 'Angeleno' plums had no internal disorders, even after five weeks of cold storage at a single low temperature. 'Pioneer' and 'Sapphire' plums were classified as climacteric and 'Songold' and 'Angeleno' were classified as suppressed climacteric based on ethylene production. The climacteric plums respired and produced ethylene at a higher rate than the suppressed climacteric plums. Climacteric plums ripened faster during shelf life than suppressed climacteric plums. Furthermore, while climacteric plums did not need a cold storage period prior to ripening, suppressed climacteric plums needed a cold storage period in order to ripen normally. The longer the cold storage period prior to transfer to higher temperatures, the faster the plums ripened and the higher the ethylene production at the higher temperature. The suppressed climacteric genotype could possibly be incorporated into plum breeding programs in order to extend the storage period and shelflife of new plum cultivars. The long storage times required to ship plums from South Africa to the export markets has necessitated research on postharvest physiology and quality of this fruit. The use of the climacteric and suppressed climacteric system to classify fruit is expected to assist in understanding the different physiological responses of the cultivars and assist in developing handling protocols. Preharvest factors, particularly light and nutrition, also playa role in postharvest quality. / AFRIKAANSE OPSOMMING: Interne verval (interne verbruining en gelverval), oorrypheid en onryp vrugte, is die hoof faktore wat die uitvoer van Suid Afrikaanse pruime negatief beïnvloed. Rypheidsprobleme ontstaan wanneer pruime gestroop-oes word, met ander woorde, al die vrugte in 'n blok of boord word geoes wanneer die meerderheid vrugte optimum rypheid bereik het. As gevolg hiervan word 'n groot persentasie vrugte vir uitvoer afgekeur, omdat hulle te ryp of nie ryp genoeg is nie. Oor die algemeen vind interne verbruining plaas wanneer vrugte onder 'n enkel lae temperatuur uitgevoer word en gelvervel vind plaas wanneer vrugte onder 'n dubbele temperatuur regime vervoer word. Gel verval kan egter in baie ryp vrugte by oes voorkom en mag by enkel lae temperature voorkom .waar dit deur interne verbruining gemaskeer sal word. Kultivars soos 'Angeleno' kan onder enkel lae temperatuur uitgevoer word sonder interne probleme, terwyl ander pruimkultivars me so uitgevoer kan word nie. So ver ons weet, word die rede hiervoor nie goed verstaan nie. Daar is baie faktore wat die kwaliteit van pruime beïnvloed, onder meer lighuishouding, minerale voeding en die rypheid waarby die pruime geoes word. Pruime wat in hoë-digtheid sisteme soos 'n V- of "spindle" groei het goeie kwaliteit vrugte met 'n lae persentasie gelverval gelewer. Dit is in teenstelling met vroeër bevindinge, waar vrugte van lae digtheid boorde hoë persentasies geverval gelewer het, veral in die onderste gedeeltes van die boom. Takke wat met 80% skadunet bedek is het hoër persentasies gelverval as die kontrole gelewer, wat aandui dat die hoof effek van die verbeterde boom struktuur op kwaliteit, verbeterde lighuishouding was. 'n Na-oes aanwending van boor op 'Songold' pruime het geen effek op die voorkoms van gelverval gehad nie, maar het die kutikula beskadig en tot hoë persentasies verrimpeling gelei. Fermheid en inteme weerstand lesings het egter getoon dat daar wel 'n effek van die boor op die selmembrane en selwande was. 'n Meer omvattende ondersoek van voor- en na-oes aanwending van boor word aanbeveel om vas te stelof daar wel 'n positiewe effek van boor in die verbetering van pruim kwaliteit is. Vier pruim kultivars, ('Pioneer', 'Sapphire', 'Songold' en 'Angeleno'), is gedurende, sowel as later as die kommersiële oesperiode geoes. In al die kultivars was die afname in fermheid kleiner as wat verwag is, en vrugte wat later geoes is het dieselfde, en soms beter, kwaliteit as die vrugte wat vroeër geoes is gehad. Pruime wat later geoes is het beter kleur en gewoonlik hoër suikers gehad. In teenstelling met wat verwag is, het pruime wat later geoes is nie meer interne verval gehad as die pruime wat vroeër geoes is nie. Dit dui die belangrikheid van optimale oesrypheid aan. 'Angeleno' het geen interne verval gehad nie, selfs na vyfweke opberging by -0.5°C. 'Pioneer' en 'Sapphire' pruirne is as klimakteries en 'Songold' en 'Angeleno' as onderdrukte klimakteries geklassifiseer, gebaseer op etileen produksie. Die klimakteriese pruime het teen 'n hoër tempo gerespireer en etileen geproduseer as die onderdrukte klimakteriese pruime. Gedurende raklewe het klimakteriese vrugte vinniger as onderdrukte klimakteriese vrugte ryp geword. Verder, terwyl klimakteriese pruime nie opbgerging by 'n lae temperatuur nodig gehad het nie, het onderdrukte klimakteriese vrugte welopberging by 'n lae temperatuur nodig gehad om normaal ryp te word. Hoe langer die koel opbergingsperiode was, hoe vinniger het die pruime ryp geword by raklewe en hoe hoër was hulle etileen produksie. Die onderdrukte klimakteriese genotipe kan moontlik in teelprogramme geïnkorporeer word om kultivars met verlengde opbergings- en raklewe te teel. Die lang vervoer tye wat benodig word om Suid Afrikaanse pruime by die uitvoer markte te kry het dit nodig gemaak om navorsing oor die na-oes fisiologie en kwaliteit van pruime te doen. Die klassifisering van pruime as klimakteries of onderdrukte klimakteries kan ons in staat stelom die verskillende fisiologiese reaksies van die kultivars te verstaan en om hanterings prosedures te ontwikkel. Voor-oes faktore, veral lighuishouding en mineraalvoecling speelook 'n rol in na-oes kwaliteit van pruime.

Thesis (Ph.D.)--Michigan State University. Dept. of Entomology, 2008. / Title from PDF t.p. (viewed on July 9, 2009) Includes bibliographical references (p. 146-160). Also issued in print.

Thesis (Ph. D.)--University of Wisconsin, 1967. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliography.

Thesis (MSc)--Stellenbosch University, 2002. / ENGLISH ABSTRACT: Historically the storage of South African plum fruit involved cold storage at single low temperatures (-O.5°C). The ever present problem of internal breakdown, however, led to the development of the dual temperature storage regime (a type of intermittent warming) which was found to restrict the level of internal breakdown. However, this temperature regime led to the development of or unmasking of gel breakdown (GB). During season one it was proposed that 'Songold' and 'Angeleno' plums could be stored at a single high temperature (7.5°C) during the shipping period (18 days) in combination with controlled atmospheres (CA). This was compared to the commercially used dual temperature regime (10 days at -O.5°C and eight days at 7.5°C). During season two the temperature regimes were adjusted to mirror the storage of the fruit from the date of harvest until the fruit is purchased. During the shipping period the dual temperature regime and the single high temperature regime were still compared. It was hypothesised that the fruit could be stored at the higher temperature in combination with CA during shipping, and this would allow the ripening of the fruit to be retarded, retaining good quality without exposure to the low, chilling inducing temperatures associated with the dual temperature regime. The storage of both plum cultivars at the single high temperature in combination with CA had a positive influence on delaying the ripening of the fruit. Most noticeable was the delay of fruit softening and the restriction of colour and GB development of the 'Songold' plums. Most importantly, these results were achieved without the fruit being exposed to the low, injurious temperatures associated with the dual temperature regime. It was, however, concluded that due to the suppressed climacteric trait of these plums more benefit could be gained from the higher temperature storage in combination with CA on climacteric plums which display stronger ripening patterns. In contrast to the plum industry, the use of CA in the storage of avocado fruit has risen to about 95% of the exported fruit. CA storage of avocados has shown positive results in retaining fruit firmness, restricting disorder development and extending the shelf life. Recently, research with l-methylcyclopropene (l-MCP) storage of avocados has been found to be as successful as CA storage and there is a belief that it will be the answer to storage for the avocado industry once registered for commercial use. During the first experiment, 'Fuerte' and 'Hass' avocados were treated with CO2 shocks (C02 levels which greatly exceed the initial intercellular concentrations of CO2 are known as CO2 shock treatments). These shock treatments were done over a series of three time periods and four CO2 concentrations for the 'Fuerte' avocados and two time periods and two concentrations for the 'Hass' avocados. Results were disappointing, as the fruit treated with CO2 were not able to retain their quality. For the second experiment, 'Fuerte' and 'Hass' avocados were treated with either CA or I-MCP, or CA and I-MCP in combination. Previous research had identified a positive synergistic effect when CA and I-MCP were combined, due to the fact that the treatments act at different points in the ethylene production process. Both the CA and I-MCP treatments, whether alone or in combination, had positive results in retaining firmness and extending the shelf life of the fruit. The treatments were also able to retain the quality of the 'Fuerte' avocados in terms of internal and, external physiological disorders. 'Hass' avocados, however, are known to be of excellent internal quality and none of the treatments had a greater percentage of sound fruit than the fruit which were stored in air. The extended ripening gained by treatment with I-MCP outweighed any increased loss due to fruit quality and in terms of the ease of application makes it superior to CA storage. However, before large-scale commercial application of I-MCP begins, much still needs to be learned about its use on avocados. Relative humidity (RH) control, forms an integral part of the storage of many fruit and vegetables. However, the difficulty in controlling and measuring RH has resulted in it being largely ignored. Research has shown that storage of fruit and vegetables at RH levels close to 95% has been able to restrict ripening and chilling injury development by decreasing the water stress on the fresh commodities during storage. During the final experiment, 'Fuerte' and 'Hass' avocados were placed at the commercial storage temperature and a chilling temperature. At each temperature, the fruit were either stored under a high or a low RH. Results were inconclusive, as the higher RH showed no signs of restricting chilling injury or any other disorders in the fruit. / AFRIKAANSE OPSOMMING: In die verlede is pruime in Suid Afrika opgeberg volgens 'n enkeltemperatuur-regime (-0.5°C). Interne verval (IV) van die pruime was 'n probleem en het gelei tot die ontwikkeling van die dubbeltemperatuur-opberging regime wat IV verhoed het. Dit het egter gelei tot die ontwikkeling of ontmaskering vanjelverval (IV). Vir seisoen een is voorgestel dat die opberging van 'Songold' en 'Angeleno' pruime gedurende die verskepingstyd (18 dae), teen 'n hoë enkeltemperatuur van 7.5°C gekombineerd met beheerde atmosfeer (BA) geskied. Dit is vergelyk met die kommersiële dubbeltemperatuur-opberging regime (10 dae by -0.5°C en agt dae by 7.5°C). Vir seisoen twee is die temperatuur regime aangepas om die opberging van die vrug vanaf die oesdatum totdat dit deur die verbruiker gekoop word, na te boots. Tydens die verskepingstyd is die dubbeltemperatuur-opberging regime steeds vergelyk met die enkeltemperatuur opberging. Die gestelde hipotese is dat die vrugte gedurende verskeping by hoë enkeltemperatuur gekombineerd met BA opgeberg kon word. Sodoende word rypwording vertraag en die kwaliteit van die vrug behou sonder dat die vrugte blootgestel word aan temperature wat koueskade sal veroorsaak. By beide kultivars het 'n hoë enkeltemperatuur, gekombineer met BA opberging, die rypwording van die vrugte vertraag. Mees opmerklik was die vertraging van die sagwording van altwee kultivars asook die vertraging van kleur ontwikkeling en JV van die 'Songold' pruime. Wat van belang is, is dat die resultate bereik is sonder dat die vrugte blootgestel was aan die lae temperature wat koueskade veroorsaak. Die onderdrukte klimakterium wat met 'Songold' en 'Angeleno' pruime verkry is toon dat pruim kultivars met sterker rypwordingspatrone meer sal baat deur opberging by hoë temperature saam met BA. In teenstelling met die pruim bedryf, word omtrent 95% van die avokado vrugte wat deur Suid Afrika uitgevoer word onder BA verskeep. BA opberging toon vir baie jare al dat dit 'n positiewe invloed op die vertraging van sagwording, die behoud van gehalte en die verlenging van die raklewe van avokados het. Onlangse navorsing het aangetoon dat I-metielsiklopropeen (I-MCP) 'n produk is wat BA opberging se plek kan inneem. Daar word geglo dit is die antwoord vir avokado opberging in Suid Afrika. Vir die eerste eksperiment het 'Fuerte' en 'Hass' avokados 'n CO2 skok behandeling ontvang (C02 vlakke wat die interne sellulêre konsentrasie van C02 oorskrei). Die skok behandelings was oor drie tydperke en vier konsentrasie vlakke gedoen vir die 'Fuerte' avokados en oor twee tydperke en twee konsentrasies vir die 'Hass' avokados. Die resultate was teleurstellend omdat die vrugte wat met die C02 behandel is nie hul gehalte kon behou nie. Gedurende die tweede eksperiment, was 'Fuerte' en 'Hass' avokados met BA of I-MCP, alleen of in kombinasie behandel. Navorsing het bewys dat daar 'n dubbelle effek is as BA en I-MCP saam gebruik word, omdat hulle etileen produksie deur verskillende maniere beheer word. Beide die BA en I-MCP behandelings, alleen of in kombinasie, het 'n positiewe effek uitgeoefen op die vrug deurdat dit fermheid behou en die raklewe verleng het. Die behandelinge het ook die kwaliteit van die 'Fuerte' avokados behou. 'Hass' is 'n avokado wat alreeds 'n baie goeie interne kwaliteit het. Vir dié rede het die vrugte wat net in lug opgeberg was die beste interne kwaliteit gehad. Maar die verlengde raklewe agv. die I-MCP behandeling is van groter belang as die kwaliteit wat verloor is. Dit, saam met die feit dat die toepassing van I-MCP behandeling baie makliker is as BA, maak dit die beter opsie. Voordat I-MCP kommersiël geregistreer is moet daar egter nog baie geleer word oor die produk sodat dit so effektief as moontlik gebruik kan word vir die opberging van avokados. Die beheer van relatiewe humiditeit (RH) word beskou as 'n groot veranderlike in die opberging van vrugte en groente. RH word egter meestal geïgnoreer in opberging omdat die beheer en meet daarvan moeilik is. Navorsing het al getoon dat indien die RH vlakke, gedurende opberging, nabyaan 95% gehou word, kan koueskade verlaag word deur die water dampdruk tekorte op die vars produkte te verlaag. Vir die finale eksperiment was 'Fuerte' en 'Hass' avokados opgeberg teen die kommersiële temperatuur sowel as 'n laer temperatuur. By beide temperature was die RH gewysig om laag of hoog te wees. Resultate was egter teleurstellend omdat die hoër RH nie koue skade of ander fisiologiese skade vertraag het nie.

No description available.

No description available.

No description available.

No description available.

No description available.