During the measurements, the freezing of turions was indicated as a transient temperature rise (freezing exotherm) by about 2–5.6 °C. On basis that water's specific heat of fusion is 335 kJ kg−1 and assuming that the turions’ dry biomass is relatively negligible (mean DW proportion is only ∼25%), the measured temperature rise of 4.3–5.6 °C, associated with turion freezing (for Aldrovanda, U. australis, U. ochroleuca and U. intermedia), is equivalent to the freezing of only approx. 5.3–7.0% of the total water content of the turions. As the majority of the turion water content is present in vacuoles and cytoplasm, it is quite obvious that the frozen water represents the extracellular water located in cell walls (see e.g., Larcher, 1995). The very rapid dynamics of freezing this water (ca. 6–12 s) may indicate the all-or-none rule of freezing. However, on the basis of the freezing temperature recordings, no freezing of the intracellular turion water content was indicated at temperatures down to −10 to −11 °C.