Xylem sap flow and pressurisation in Acer pseudoplatanus. L

O'Malley, Philip E.R (1979) Xylem sap flow and pressurisation in Acer pseudoplatanus. L. PhD thesis, University of Glasgow.

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This thesis presents the results of an investigation into the enigmatic phenomenon of xylem sap pressurisation (or exudation) from dormant trees of Acer pseudoplatanus. L. The characteristics of the system were established, through initial experimentation, and found to relate to previous studies of exudation from trees of Acer saccharum (Marsh), More detailed investigations were then undertaken. Studies were performed both in the field, using mature trees, and in the laboratory, using stem sections. Previous hypotheses appeared inadequate to account for the new observations and an alternative mechanism was conceived. This new hypothesis, based on sap priming through internal frosting, is proposed. Experimentation revealed that sap uptake, caused by sub-atmospheric stem pressures during cooling, was biphasic. The first phase of uptake was shown to be the result of thermal effects prior to freezing. The second phase was associated with freezing of sap within the tissue. Experiments already described suggest that uptake of sap (or water) before ice formation is a consequence of contraction of gas and liquid and dissolution of gases. The contribution of this phase to subsequent exudation is significantly less than responses induced by freezing of sap (eg. sap absorption before freezing, for change in stem temperature of 10

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Additional Information: Adviser: J A Milburn
Keywords: Plant sciences
Date of Award: 1979
Depositing User: Enlighten Team
Unique ID: glathesis:1979-72261
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 24 May 2019 15:12
Last Modified: 24 May 2019 15:12
URI: https://theses.gla.ac.uk/id/eprint/72261

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