Evaluation of the importance of ionic and osmotic components of salt stress on the photosynthetic efficiency of epiphytic lichens

Abstract

Salt stress can significantly disrupt the functioning of lichens which are self-sufficient symbiotic organisms inhabiting various severe environments. The aim was to test the effect of salt and sucrose on the photosynthetic efficiency of two selected epiphytic lichens inhabiting the interior of the land. Firstly, we compared the effect of salt and sucrose solutions of different concentrations. Secondly, the effect of salt and sucrose solutions with identical osmotic pressures was compared. The results showed that short-term salt stress leads to a significant reduction of FV/FM, greater changes in chlorophyll fluorescence parameters and OJIP transients compared to the osmotic effects induced by sucrose. This proved that the negative impact of salt stress is associated primarily with ionic effects. The most symptomatic effect of the ionic stress was a significant reduction of the utilisation of trapped energy in electron transport and thereby down-regulation of electron transfer. Since lichens are resistant to a temporary lack of water, ionic stress could have more serious consequences than osmotic stress itself. Hypogymnia physodes was more sensitive to salt stress than Pseudevernia furfuracea, but the reduction of photosynthetic efficiency was not permanent since after 24 h FV/FM returned to the level characteristic for healthy lichens. Nevertheless, repeated exposure to salt may reduce the vitality of lichens growing along communication routes sprinkled with salt in the winter season. Finally, the changes in certain JIP-test parameters were stronger than FV/FM, thus they could be better indicators of salt stress in lichens.

The Key Role of Cyclic Electron Flow in the Recovery of Photosynthesis in the Photobiont during Rehydration of the Lichen Cladonia stellaris

“…Prolonged drying and dehydration cause greater damage to the structure and functional recovery of PSII than short-term desiccation. This is in line with some previous studies that showed that only a prolonged stay in the desiccated state caused significant degradation of chlorophyll [41,42]. The desiccation tolerance is species-specific and depends on the speed, intensity and duration of water loss during dehydration [6].…”

ROS scavenging and ion homeostasis is required for the adaptation of halophyte Karelinia caspia to high salinity

“…Chlorophyll a fluorescence parameters are regarded as important tools for analyzing the functionality of photosystems under salt stress. The F v /F m is a sensitive indicator of photo-inhibition of PSII under stress ( Chowaniec and Rola, 2022 ). In K. caspia , F v /F m increased in salt treatments compared with control, indicating that salinity promoted the photosynthetic efficiency of PSII.…”

Changes in Photosynthetic Activity of the Lichen Cladonia mitis and the Moss Pleurozium schreberi under Artificial High-Energy Lighting in Laboratory Conditions

“…The photosynthetic activity of lichens is strongly related to the hydration level of their thalli. However, the amount of water in their thalli depends on climatic conditions (Chowaniec and Rola, 2022;Lange et al, 1993;ten Veldhuis, 2020). Thallus dehydration leads to a gradual loss of photosynthetic activity of the photobiont, causing changes in PS II, characterized by a decrease in the efficiency of absorbed energy transmission (Chowaniec and Rola, 2022).…”