Antarctic Science

Table of Contents - 2008 - Volume 20, Issue 06  

Biological Sciences

Deep dehydration of Umbilicaria aprina thalli observed by proton NMR and sorption isotherm

H. Harańczyka1 c1, M. Baciora1 and M.A. Olecha2a3

a1 Institute of Physics, Jagiellonian University, Cracow, Poland

a2 Institute of Botany, Jagiellonian University, Cracow, Poland

a3 Department of Antarctic Biology, Polish Academy of Sciences, Warsaw, Poland

Abstract

The initial stages of Umbilicaria aprina Nyl. hydration (starting from the hydration level Δm/m0 = 0.048 ± 0.004) were observed using hydration kinetics, sorption isotherm and proton NMR. The thalli were hydrated from gaseous phase. The total saturation hydration level obtained at the relative humidity p/p0 = 100% was Δm/m0 = 0.848 ± 0.009. The hydration courses revealed i) a fraction of very tightly bound water (Δm/m0 = 0.054 ± 0.011, short hydration time constant, thyd), ii) a fraction of tightly bound water [Δm/m0 = 0.051 ± 0.038, thyd = (4.7 ± 2.6) h], and iii) a loosely bound water pool [thyd = (31.0 ± 1.9) h] for higher values of target humidity. The sorption isotherm of U. aprina was fitted well using Dent model. The relative mass of water saturating primary binding sites was ΔM/m0 = 0.054, which is close to the water fractions. Proton FIDs detected (i + ii) the immobilized tightly bound water fraction, L1, and iii) the mobile, loosely bound water pool L2. The hydration dependence of the proton liquid signal suggests the presence of a significant contribution from a water soluble solid fraction in the thallus. Sorption isotherm fitted to NMR data showed the absence of ‘sealed’ water fraction trapped in pores of the thallus.

(Received July 05 2007)

(Accepted February 22 2008)

Key words

Correspondence:

c1 hubert.haranczyk@uj.edu.pl

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