Physiological response of the bioindicator Ramalina farinacea in relation to atmospheric deposition in an urban environment

Laboratory and field measurements of water relations, photosynthetic parameters, and hydration traits in macrolichens in a tropical lower montane rainforest in Thailand

Ecophysiological studies of lichens in tropical Asia are rare, and additional studies can increase the understanding of lichen life in this region. The main aim of this study was to observe the relationships between water availability and photosynthetic parameters, as well as hydration trait parameters, in macrolichens during the rainy and dry seasons in a tropical forest. A total of 11 lichen species growing in a lower montane rainforest in Thailand were collected and studied. The results clearly showed that the specific thallus mass (STM), net photosynthetic rate (Pn), the potential quantum yield of primary photochemistry (Fv/Fm), chlorophyll content, and carotenoid content of almost all lichens were lower in the dry season than in the rainy season. Field measurements in the dry season revealed that only the foliose chlorolichen Parmotrema tinctorum was metabolically active and exhibited slight carbon assimilation. In the rainy season, all lichens started their photosynthesis in the early morning, reached maximal values, declined, and ceased when the thalli desiccated. The photosynthetically active period of the lichens was approximately 2-3 h in the morning, and the activities of the cyanolichens ended approximately 30 min after the chlorolichens. The hydration trait parameters, including the STM, maximal water content (WCmax), and water holding capacity (WHC), were greater in the cyanolichens. In addition, the maximal Pn (Pnmax) and optimal water content (WCopt) for Pn were also greater in the cyanolichens, but the maximal Fv/Fm (Fv/Fmmax) was lower. The cyanolichens compensated for their inability to use humid air to restore photosynthesis by having higher water content and storage, higher photosynthetic rates, and longer photosynthetically active periods. This study provides additional insights into lichen ecophysiology in tropical forests that can be useful for lichen conservation.

Physiological alterations and heavy metal accumulation in the transplanted lichen Pyxine cocoes (Sw.) Nyl. in Lucknow city, Uttar Pradesh

Air pollution has become a major concern due to its detrimental effects on living beings. The present study is aimed at assessing the current status of air pollution in Lucknow city using lichen transplantation technique and assesing its effect on physiology of Pyxine cocoes. The samples of P. cocoes were collected from relatively pollution-free area Malihabad and transplanted in 10 designated sites in five regions for 30 days. Various parameters such as heavy metals, chlorophyll pigments, carotenoid, chlorophyll degradation, and electrolyte conductivity were estimated in transplanted lichens. The study revealed that the concentration of all 10 heavy metals was higher in all transplanted samples than in the control sample, which was found in order of Al > Fe > Mn > Zn > Cu > Cr > Pb > Ni > Co > Cd. Among all 10 transplanted sites, the significantly increased accumulation of aluminum (5.11 to 5.47 µg L-1), iron (4.73 to 5.46 µg L-1), manganese (110.99 to 144.58 µg g-1), and zinc (87.96 to 97.40 µg g-1) was found in Charbagh, Qaisarbagh, and Alambagh sites. Further, in all samples, chlorophyll a (3.98 µg L-1), chlorophyll b (1.22 µg L-1), total chlorophyll (5.20 µg L-1), and chlorophyll degradation (0.55 µg g-1) were significantly decreased, whereas elevated levels of carotenoid (0.71 µg g-1), and electrolyte conductivity (64.99 µS cm-1), were observed. The scanning electron microscope (SEM) investigated the morphological changes in transplanted lichen samples, and significant damage to the anatomy of mycelium was found in most of the polluted site's samples, which correlated with the pollution levels. The present study clearly demonstrated that the transplanted lichen P. cocoes is an efficient bioaccumulator and bioindicator of air quality in urban environments.

Lichen biomonitoring of seasonal outdoor air quality at schools in an industrial city in Thailand

Poor air quality in school environments causes adverse health effects in children and decreases their academic performance. The main objective of this study was to use lichens as a biomonitoring tool for assessing outdoor air quality at schools in the industrial area of Laem Chabang municipality in Thailand. Thalli of the lichen Parmotrema tinctorum were transplanted from an unpolluted area to nine schools in the industrial area and to a control site. The lichens were exposed for four periods in the dry, hot, early rainy, and late rainy seasons, for 90 days each. The concentrations of 14 elements, including As, Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb, Sb, Ti, V, and Zn, were determined using inductively coupled plasma‒mass spectrometry (ICP‒MS), and 8 physiological parameters were measured. The concentrations of all 14 investigated elements were clearly higher at the schools than at the control site. The contamination factors (CFs) suggested that 9 out of the 14 elements, including As, Cd, Co, Cr, Cu, Mo, Pb, Sb, and Ti, heavily contaminated the school environments, especially Pb, the concentration of which was 3 to 11 times higher than at the control site. The most polluted time was the hot season as evidenced by the investigated elements, and the least polluted time was the late rainy season. The pollution load indices (PLIs) demonstrated that schools in the inner and middle zones clearly had higher pollution loads than the schools in the outer zone during the rainy seasons, while the hot and dry seasons showed similar pollution levels in all zones. The vitality indices (VIs) showed that the lower lichen vitalities at most schools were observed during the dry season and at the schools in the inner and middle zones. Accordingly, the air performance indices (APIs) revealed that poorer air quality at most schools was found during the dry season and at the schools in the inner and middle zones. This study clearly showed that the transplanted lichen P. tinctorum was an effective bioindicator of air quality in school environments. The results illustrated that all studied schools were contaminated by air pollutants; therefore, improving air quality at the schools is crucial and should be an urgent issue for maintaining good health and may benefit children's academic achievements and careers in the long run.