Effects of salinity stress on cellular location of elements and photosynthesis in Ramalina canariensis Steiner

Abstract

The impact of incubation in saline solutions of different concentrations on the uptake and cellular location of essential elements (Na + , K + , Mg 2+ and Ca 2+ ), and its effects on membrane integrity and on the photosynthetic apparatus, were investigated in the lichen Ramalina canariensis Steiner. Saline incubation resulted in a rapid uptake of Na + and Mg 2+ in the cell wall fraction, whereas in the intracellular fraction the accumulation of Na + was slower. No changes were observed for intracellular Mg 2+ , suggesting that no generalized membrane damage occurred. Concomitantly with the increase in intracellular Na + , there was a specific loss of K + from the cell interior, indicating that membrane permeability may have been compromised. Incubation in a 100% artificial sea water solution reduced the maximum photochemical efficiency of Photosystem II (F v /F m ) by 17% after 5 min, and this inhibition increased with incubation time. In samples incubated in 100% artificial sea water solution for 2 h followed by 2 h incubation in deionized water, ion distribution and F v /F m did not recover to control values. The present findings show the importance of determining the cellular location of elements when assessing their physiological impact. Results indicate that saline stress may irreversibly impair photosynthesis, thus compromising lichen vitality.

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

“…Kalaji et al 2018 ; Zhao et al 2019 ; Akhter et al 2021 ); however, there are only a few studies that tested the effect of salt stress on lichens (e.g. Matthes-Sears et al 1987 ; Nash III and Lange 1988 ; Smith and Gremmen 2001 ; Matos et al 2011 ; Malaspina et al 2015 ). Most of the previous studies analysed the issue in the context of lichens naturally exposed to sea salt, and even if they were experimental studies, they were concerned about the impact of seawater on lichen physiology.…”

“…For example, Smith and Gremmen ( 2001 ) found that salinity did not significantly influence the CO 2 assimilation rate in a shore-zone lichen Turgidiusculum complicatulum . On the contrary, incubation in a 100% artificial seawater solution of Ramalina canariensis caused a considerable and irreversible reduction in F V /F M (Matos et al 2011 ). The situation is more complicated since Nash III and Lange ( 1988 ) showed that the degree of sensitivity to salt stress of a certain species is proportional to the distance from the sea coast where the lichens grow.…”

“…Water loss is a dynamic phenomenon and certain acclimation can occur in lichens (Lange and Green 2005 ). Nevertheless, the accumulation of saline elements in thalli may induce both strong dehydration in lichens, but also ionic imbalances, and a deep loss in net photosynthesis of lichen photobionts (Matos et al 2011 ). Moreover, high salinity induces hyperosmotic shock that generates oxidative stress and causes various metabolic disorders (Erdman and Hagemann 2001 ; Delmail et al 2013 ).…”

“…The exposure to dehydration leads to a gradual loss of photosynthetic activities of the photosynthetic partner, as evidenced by changes in the photosystem II (PSII) and is manifested by a decrease in the efficiency of transfer of the energy absorbed by it. The reduction of the maximum efficiency of PSII can lead to irreversible damage within it and consequently viability reduction of the whole thallus (Matos et al 2011 ). The rate of respiration is also slowed down as a result of the gradual loss of pressure potential in the cells (Hajek et al 2006 ).…”

Risks to biodiversity from hydraulic fracturing for natural gas in the Marcellus and Utica shales

“…15 Four northeastern amphibian species have been shown to be adversely affected by approximately 50-1,000 mg L −1 chloride, depending on the species and life stage, 22 suggesting that small amounts of HVHHF wastewater could render breeding habitats unsuitable. Many lichens, [23][24][25] liverworts, 26 sphagnum mosses, [27][28][29] conifers, 30,31 aquatic plants, 32,33 and bog plants 34 are also sensitive to salt; numerous streams are already salinized from road deicing. 35 Furthermore, lichens [36][37][38][39][40] and stoneworts [41][42][43] can be harmed by heavy metals.…”