Thermodynamic analysis of the physical state of water during freezing in plant tissue, based on the temperature dependence of proton spin-spin relaxation

M. M. Millard, O. Veisz, D. T. Krizek, M. Line

Research output: Contribution to journalArticle

16 Citations (Scopus)

Abstract

Multi-proton spin-echo images were collected from cold-acclimated winter wheat crowns (Triticum aestivum L.) cv. Cappelle Desprez at 400 MHz between 4 and -4 °C. Water proton relaxation by the spin-spin (T2) mechanism from individual voxels in image slices was found to be mono-exponential. The temperature dependence of these relaxation rates was found to obey Arrhenius or absolute rate theory expressions relating temperature, activation energies and relaxation rates. Images whose contrast is proportional to the Arrhenius activation energy (Ea), Gibb's free energy of activation (ΔG‡), enthalpy of activation (ΔE‡), and the entropy of activation (ΔS‡) for water relaxation on a voxel basis were constructed by post-image processing. These new images exhibit contrast based on activation energies rather than rates of proton relaxation. The temperature dependence of water proton T2 relaxation rates permits prediction of changes in the physical state of water in this tissue over modest temperature ranges. A simple model is proposed to predict the freezing temperature of various tissues in wheat crowns. The average Ea and ΔH‡ for water proton T2 relaxation over the above temperature range in winter wheat tissue were -6.4±14.8 and -8.6±14.8 kJ mol-1, respectively. This barrier is considerably lower than the Ea for proton translation in ice at 0 °C, which is reported to be between 46.0 and 56.5 kJ mol-1.

Original languageEnglish
Pages (from-to)33-42
Number of pages10
JournalPlant, Cell and Environment
Volume19
Issue number1
Publication statusPublished - 1996

Fingerprint

Thermodynamics
thermodynamics
Freezing
protons
plant tissues
Protons
freezing
activation energy
Triticum
Temperature
Water
temperature
water
Crowns
tree crown
winter wheat
freezing point
Ice
Entropy
enthalpy

Keywords

  • Activation energy
  • Cold acclimation
  • Freezing injury
  • NMR imaging
  • Non-freezable water
  • Poaceae
  • Spin-spin relaxation
  • Temperature dependence
  • Triticum aestivum L
  • Water dynamics

ASJC Scopus subject areas

  • Plant Science

Cite this

Thermodynamic analysis of the physical state of water during freezing in plant tissue, based on the temperature dependence of proton spin-spin relaxation. / Millard, M. M.; Veisz, O.; Krizek, D. T.; Line, M.

In: Plant, Cell and Environment, Vol. 19, No. 1, 1996, p. 33-42.

Research output: Contribution to journalArticle

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