Fig. 4

TEM micrographs of the higher freshwater plant Lemna sp. (a, b), the higher alpine plant Ranunculus glacialis (c, d) and the higher alpine plant Pinus mugo (e–f) after freezing (b, d, f) in comparison to temperate controls (a, c, e). a 20 °C control of Lemna shows vacuole (v), mitochondria (m), chloroplast (chl), endoplasmic reticulum (er) and nucleus (n). bLemna leaf after − 2 °C freezing shows chloroplast (chl) with enlarged starch grains (sg), endoplasmic reticulum (er) and signs of degradation and autophagic structures (at). c 4 °C control of Ranunculus shows mitochondria (m), peroxisome (p), multivesicular bodies (mvb), endoplasmic reticulum (er) and a part of the chloroplast (chl). dRanunculus leaf after − 5 °C freezing with aggregated mitochondria (m) and signs of degradation and autophagic structures (at). e 20 °C control of Pinus shows mitochondria (m), chloroplast (chl) and endoplasmic reticulum (er). fPinus needle after − 6 °C freezing shows chloroplast (chl), mitochondria (m) and vacuole (v)