*2.3. Vitality of the Lichen Photobiont*

Photosynthetic parameters were previously used to assess the vitality of *L. pulmonaria* [54–59]. Here, chlorophyll (Chl) *a* fluorescence emission and total chlorophyll content were used as a proxy for the overall vitality of the transplants. The measurements of chlorophyll *a* fluorescence were carried out by a Plant Efficiency Analyzer Handy PEA (Hansatech Ltd., Norfolk, UK). Thalli were kept hydrated (sprayed with mineral water) and dark-adapted for at least ten minutes (covered with a black velvet cloth) before the measurements. Each sample was illuminated using the clip for 1 s with a saturating excitation pulse (3000 μmol(photon) s−<sup>1</sup> m−2) of red light (650 nm) from a LED into the fluorometer sensor. All fluorescence induction curves were recorded up to 1 s. The condition of the samples was expressed by the maximum of the quantum yield of primary photochemistry as inferred from fluorescence data: FV/FM = (FM − F0)/FM, where F<sup>v</sup> = (F<sup>m</sup> − F0) is the variable fluorescence, F0 is the calculated basal fluorescence and Fm is the maximum Chl *a* fluorescence.

The chlorophyll content of the samples, expressed as total chlorophyll per m2 of biological material (mg m<sup>−</sup>2), was measured by a Chlorophyll Content Meter-300 (Opti-Sciences CCM-300, Hudson, NH, USA), which gauged the chlorophyll content based on reflectance and/or absorbance of radiation by chlorophyll molecules. The method provided accurate readings also in lichens, comparable to those obtained using the classical dimethyl sulphoxide (DMSO) extraction method [60].
