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EXTRACELLULAR FREEZING IN EQUISETUM HYEMALE
Author(s) -
Niklas Karl J.
Publication year - 1989
Publication title -
american journal of botany
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.218
H-Index - 151
eISSN - 1537-2197
pISSN - 0002-9122
DOI - 10.1002/j.1537-2197.1989.tb11355.x
Subject(s) - pith , shoot , extracellular , biology , botany , horticulture , biophysics , microbiology and biotechnology
Extracellular freezing occurs within the pith cavities of Equisetum hyemale L. aerial shoots when they are exposed to subfreezing temperatures. The weight of plugs of ice within pith cavities correlates linearly with the weight of internodal tissues (r 2 = 0.974, N = 10); ice plugs are 32–38% (33 ± 1.8%) the weight of intact shoots. Upon thawing, internodal water is gradually reabsorbed by excised shoots. Extracellular freezing can be induced by exposing excised shoots to gradually decreasing temperatures (5 C/day) to –20C, and is associated with a reduction in tissue water potential. Data indicate that internodal tissues behave as osmometers and dehydrate until reaching equilibrium with the chemical potentials of extracellular fluids within internodal pith cavities. Upon thawing, internodal water is reabsorbed by excised shoots and tissue water potential increases. Extracellular freezing may operate as a mechanism that reduces intracellular ice formation and tissue damage during extremely cold weather.