Magnetic resonance imaging of tissue-specific thermal responses of geranium stem in vivo

1. 1. Tissue-specific variations in the responses of geranium stems to hyperthermia were investigated in vivo by acquiring tissue water proton spin-spin (T 2) relaxation images at different sample temperatures and calculating the apparent activation energy (E a) and entropy (ΔS ‡) for each image vox...

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Bibliographic Details
Published in:Journal of thermal biology 1997-04, Vol.22 (2), p.117-126
Main Authors: Caldwell, Charles R., Millard, Merle M., Line, Michael J.
Format: Article
Language:English
Subjects:
geraniaceae
geranium
heat tolerance
NMR imaging
Pelargonium xhortorum
thermal damage
thermodynamics
tissue water
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Summary:1. 1. Tissue-specific variations in the responses of geranium stems to hyperthermia were investigated in vivo by acquiring tissue water proton spin-spin (T 2) relaxation images at different sample temperatures and calculating the apparent activation energy (E a) and entropy (ΔS ‡) for each image voxel [(39 μm × 39 μm) × 500 μm]. 2. 2. After partitioning the images by tissue type, Eyring analyses of the temperature dependence of water proton T 2 relaxation demonstrated increases in E a or ΔH ‡ when the sample temperature exceeded 26.5, 45.7, 32.4 and 31.1°C for the pith parenchyma, fibrous sheath/vascular tissues, cortical parenchyma/epidermal tissues and whole stem, respectively. 3. 3. The results suggest that the changes in T 2 thermodynamics are caused primarily by direct temperature-dependent variations in the physical state of tissue water, while a standard viability assay measures thermally-induced protein denaturation. 4. 4. This is apparently the first in vivo demonstration of tissue-specific variations in a plant response to hyperthermia.
ISSN:0306-4565
1879-0992
DOI:10.1016/S0306-4565(97)00001-6