Studies of calcium transport in apple fruit

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dc.contributor.advisor Ferguson, I.B. en
dc.contributor.advisor Dromgoole, F.I. en Harker, F. R. (Frederick Roger), 1960- en 2007-09-03T07:24:00Z en 2007-09-03T07:24:00Z en 1986 en
dc.identifier THESIS 87-200 en
dc.identifier.citation Thesis (PhD--Botany)--University of Auckland, 1986 en
dc.identifier.uri en
dc.description Full text is available to authenticated members of The University of Auckland only. en
dc.description.abstract The work reported in this thesis involves an investigation of non-vascular Ca2+ transport in tissue of apple fruit and uptake of Ca2+ through the apple fruit skin. This was carried out by following the transport of 45Ca2+ through discs of apple fruit cortical tissue and 45Ca2+ penetration across isolated cuticles. Discs were clamped between two chambers containing solutions and the movement of 45Ca2+ was followed across the disc from one chamber into the other. 45Ca2+ appeared to diffuse through the disc apoplast and was also influenced by exchange across the negatively-charged cell wall continuum. Seasonal changes in disc permeability were related to the varying composition of apple cortical tissue. During fruit development the relative size of the apoplast and the cell wall content of apple cortical tissue decreased due to cell expansion and the enlargement of airspaces. The transport capacity of discs decreased due to the reduction in cell wall content, and consequently the rate of 10-6 M 45Ca2+ transport was higher across discs cut from immature fruit than across discs cut from mature fruit. Similar developmental changes in the mobility of Ca2+ are expected in whole fruit. When 10-2 M 45CaCl2 was provided in the loading chamber, transport mainly occurred by diffusion through the Water Free Space and infiltrated airspaces since the exchange pathway became saturated at high 45Ca2+ concentrations. Cuticles were isolated enzymically and 45Ca2+ penetration followed in a system similar to that used for disc transport measurements. A1though there was an increase in cuticle thickness during fruit development, there was no change in the proportion of wax in the cuticle. There was little penetration through the cuticle, most proceeding through non-functional stomata known as lenticels, or through cracks. The number of lenticels on the apples remained approximately constant for most of the season, with the result that as apples expanded, the frequency of lenticels on the fruit surface decreased. However, the permeabi1ity of individual lenticels increased during fruit development. Penetration of 45Ca2+ across cuticles could be increased using surfactants. The addition of Armoblen T25 and Tween 20 to the solutions in the chambers doubled the rate of penetration. However, the addition of Agral LN had little effect, and the cuticles became impermeable after the addition of Armoblen NPX. The increases in penetration were mainly observed when the surfactants were exposed to the inner non-waxy cuticle surface. This may provide evidence supporting the suggestion that surfactants increase cuticle permeability by altering its porosity when they have direct access to the cutin and polysaccharide matrix. Surfactants might have been unable to partition into the cuticle when exposed to the outer waxy surface. The results from these investigations are discussed in relation to the preharvest Ca2+ sprays and the postharvest Ca2+ dips, used to reduce the incidence of bitter pit in apple fruit. en
dc.language.iso en en
dc.publisher ResearchSpace@Auckland en
dc.relation.ispartof PhD Thesis - University of Auckland en
dc.relation.isreferencedby UoA9910451914002091 en
dc.rights Restricted Item. Available to authenticated members of The University of Auckland. en
dc.rights Items in ResearchSpace are protected by copyright, with all rights reserved, unless otherwise indicated. en
dc.rights.uri en
dc.title Studies of calcium transport in apple fruit en
dc.type Thesis en Botany en The University of Auckland en Doctoral en PhD en
dc.rights.holder Copyright: The author en

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