|0.15| °C in defined time windows, and that RH affected the shape of these thermal fingerprints. We demonstrated that IRT can also be used to assess the viability of the lichens Lobaria pulmonaria, Pseudevernia furfuracea and Peltigera leucophlebia. No clear relationship between aerobic metabolism and the shape of thermal fingerprints was found. Conclusions Infrared thermography appears to be a promising method for the diagnosis of viability of desiccation-tolerant tissues at early stages of water uptake. For seeds, it is possible to diagnose viability within the first hours of rehydration, after which time they can still be re-dried and stored until further use. We envisage our work as a baseline study for the use of IR imaging techniques to investigate physiological heterogeneity of desiccation tolerant life forms such as lichens, which can be used for biomonitoring, and for sorting live and dead seeds, which is potentially useful for the seed trade."/>
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Fig. 3 | Plant Methods

Fig. 3

From: Non-invasive diagnosis of viability in seeds and lichens by infrared thermography under controlled environmental conditions

Fig. 3

Effects of imbibition in water vapour and liquid water, and oxygen, on the thermal fingerprints of L. pulmonaria thallus discs (Experiment 2). Left panels show imbibition under normoxia (air) and right panels show imbibition under anoxia (air was replaced by flushing with N2 gas). "Live" samples (green) were untreated and "dead" samples (red) were killed by microwaving the hydrated thallus discs at 800 W for 30 s. a, b Viability of lichen discs before (t0; closed symbols) and after (t170min; open symbols) the experiment, assessed by the maximal photochemical efficiency of photosystem II. Data show means ± SE (n = 15 lichen discs). Green and red lower-case letters above the bars denote significant differences between treatments ("live", "dead") and between start (t0) and end (t170min) of the experiment (P < 0.05; Kruskal–Wallis test). c, d Moisture content (MC) of L. pulmonaria thallus discs during rehydration. Data show means ± SE of a second set of thallus discs (n = 5). The asterisk indicates that "life" and "dead" thallus discs differed significantly (P < 0.05; Mann–Whitney U test). e, f Thermal fingerprints of "live" and "dead" thallus discs showing median values of relative temperature (rT) during imbibition. Data are medians of n = 15 "live" and n = 15 "dead" thallus discs. g, h Differences between the fingerprints of "live" and "dead" thallus discs (ΔTlive–dead). Horizontal green bars indicate the time windows in which the T values of "live" thallus discs differed significantly from that of "dead" ones (P < 0.05; Two Sample t-test). Open blue horizontal bars indicate the time periods of hydration by water vapour and closed blue bars indicate imbibition in liquid water from below

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