Drought-tolerant cyanobacteria and mosses as biotechnological tools to attain land degradation neutrality

The induction of biocrusts through inoculation-based techniques has gained increasing scientific attention in the last 2 decades due to its potential to address issues related to soil degradation and desertification. The technology has shown the most rapid advances in the use of biocrust organisms, particularly cyanobacteria and mosses, as inoculants and biocrust initiators. Cyanobacteria and mosses are poikilohydric organisms – i.e., desiccation-tolerant organisms capable of reactivating their metabolism upon rehydration – that can settle on bare soils in abiotically stressing habitats, provided that selected species are used and an appropriate and customized protocol is applied. The success of inoculation of cyanobacteria and mosses depends on the inoculant's physiology, but also on the ability of the practitioner to identify and control, with appropriate technical approaches in each case study, those environmental factors that most influence the inoculant settlement and its ability to develop biocrusts. This review illustrates the current knowledge and results of biocrust induction biotechnologies that use cyanobacteria or mosses as inoculants. At the same time, this review's purpose is to highlight the current technological gaps that hinder an efficient application of the technology in the field.

Interspecific differences in photosynthetic efficiency and spectral reflectance in two Umbilicaria species from Svalbard during controlled desiccation

This study aimed to evaluate the effective photosynthetic quantum yield (FPSII) and the Photochemical Reflectance Index (PRI) for assessment of photosynthetic performance of two Umbilicaria lichens during gradual desiccation of their thalli. U. cylindrica andU. decussata exhibited curvilinear relationship (S-shape curve) of decreasing FPSII values with decreasing water potential (WP) of thalli. During initial phase of desiccation (WP from 0 to -10 MPa), no decrease of FPSII was apparent, further desiccation (WP from -10 to -20 MPa) led to fast FPSII decrease from 0.6 to 0.1 indicating strong inhibition of photosynthetic processes. Critical WP at which photosythetic processes are fully inhibited was found bellow -25 MPa in both lichen species. Photochemical Reflectance Index (PRI) exhibited curvilinear increase with thalli desiccation (decreasing WP). At full thallus hydration, the PRI reached the value of -0.18 in both species. Under strong dehydration (WP from -20 to -30 MPa), however, U. cylindrica showed somewhat lower value (-0.04) than U.decussata (-0.02 MPa). PRI to WP relationship is discussed and compared to existing evidence from higher plants and poikilohydric organisms.

A new method for the accurate in situ monitoring of chlorophyll a fluorescence in lichens and bryophytes

A new method has been developed to measure chlorophyll a fluorescence of bryophytes and lichens in situ in the field. Specially designed aluminium stands fixed to rocks or other suitable substrata allow several cryptogam thalli to be measured sequentially with only one pulse amplitude modulated (PAM) chlorophyll a fluorescence analyser. The stands guarantee a fixed position for the fluorescence probe in relation to the thallus surface and also provide the possibility to darken the thalli so that both the apparent and the potential quantumefficiency of PSII (▵F/Fm′ and Fv/Fm) can be measured. A detailed analysis of chlorophyll a quenching parameters (qP, qN, NPQ) can also be performed with only minimal changes in the environmental conditions. The method allows easy detection of periods of metabolic activity and inactivity of the poikilohydric organisms. In combination with gas–exchange and microclimatic measurements the carbon balance also can be calculated. The method is described in detail and examples of its application in the field are presented