Differential responses of certain lichen species to sulfur-containing solutions under acidic conditions as expressed by the production of stress-ethylene

Unraveling the ameliorative potentials of native lichen Pyxine cocoes (Sw.) Nyl., during COVID 19 phase

Due to the rapid increase in the novel coronavirus virulence, the entire world implemented the practice of lockdown along with the constraint of human movement. The obligation of quarantine halted most of the commercial and industrial movement that prominently disturbed the distinct key environmental parameters directly associated with the plant's and animal's health conditions. In this regard, the research aims to study the sudden shut-off of vehicular activity impact on the naturally growing lichen of the genus Pyxine cocoes. The results showed an increase in the pigments, Fv/Fm ratio, and phytohormones during the lockdown and concurrently the decreasing levels in the post-lockdown period. Interestingly, modulations in the phytohormones occur in the lockdown period as compared to the post-lockdown period. The metals Al, Cr, and Fe show the highest increasing trends in the unlocking period, whereas As, Cd, Pb, Cu, Hg, Mn, and Zn show very little variation during the running and post-lockdown phases. The lichen photosynthetic activity justifies further examination as initial biological indicators of the abrupt environmental variations prompted by such types of atmospheric situations and, to a greater extent, for the risk assessment in the near future. In conclusion, stress-phytohormone and amino acids play a significant role as stress reducers. Although lichens are well known for long environmental assessment, the present study will provide qualitative and quantitative variation in physiochemical changes in the short term and sudden environmental fluctuations. HIGHLIGHTS: • Qualitative and quantitative variation in biochemical parameters in lichen during and post-lockdown period was analyzed. • Stress-phytohormone and amino acids play a significant role as stress reducers. • Selectivity sequence reflection in heavy metal accumulation may be used in future studies.

Responses of antioxidants in the lichen Ramalina lacera may serve as an early-warning bioindicator system for the detection of air pollution stress

The aim of this study was to identify, in the lichen Ramalina lacera, antioxidants that could provide indications of air pollution stress, and respond earlier than traditionally used structural/physiological parameters. The pollution-sensitive lichen R. lacera was transplanted from its relatively unpolluted natural habitat to two air-polluted sites for a period of up to 6 months. The superoxide dismutase and catalase activities, total water- and lipid-soluble low-molecular-weight antioxidant capacities and chlorophyll b/chlorophyll a ratios were assessed every 6 weeks. The earliest signs of oxidative stress were detected in the activities of fungal copper/zinc-superoxide dismutase, algal iron-superoxide dismutase and water-soluble low-molecular-weight antioxidants, which increased significantly as early as 42 days after exposure to pollution. Catalase activity increased in lichens transplanted to the polluted sites after 90 days. All activities decreased towards the end of the experiment. The impact of air pollution on R. lacera, using the traditionally employed parameter of chlorophyll b/chlorophyll a ratio, was only detected after 6 months of exposure to air pollution. Our results indicate that antioxidant parameters may serve as improved early-warning indicators of air pollution stress in lichens.

Biological monitoring: lichens as bioindicators of air pollution assessment--a review

Often as part of environmental impact studies and, above all, to obtain authorisations in accordance with prescriptions from the Ministry for the Environment (Italy), surveys and controls that use biological indicators are required. This is because such indicators are valid instruments for evaluating the quality of the air ensuing from the subject (often an industrial plant) of the Environmental Impact Assessment (EIA). In this context, this paper aims to analyse some of the theoretical aspects of biological monitoring and to provide a progress report on the use of lichens as bioindicators of air quality, with a particular eye to the situation in Italy. The object of this paper is that of pointing out the most important lines in the current state of knowledge in this field, evaluating the methodological applications and their advantages/disadvantages with respect to traditional surveying methods.