Does the soil microbial community facilitate Mimosa pudica's biological performance under abiotic stress? Growth, tolerance mechanisms, and seismonastic behaviour.

Climate change effects such as soil salinisation or drought dramatically affect native and potentially invasive plant species. Mimosa pudica, originally native to South America but spread to Africa and Asia, exhibits great adaptability to disturbed environments in tropical and subtropical areas. It has become a model organism for studying thigmomorphogenetic behaviour due to its ability to display fast responses to mechanical stimuli. We investigated the effects of salt and water stresses on M. pudica in interaction with a Mediterranean coastal dune microbial community by growing plants on soils collected from dunes near Valencia, Spain. Plant biomass, potential mechanisms of stress tolerance, seismonastic response, and phenology were assessed. Abiotic stress, particularly salt stress, adversely affects plant performance and seismonasty. Mimosa pudica, however, displayed the blockage of Na+ transport at the root level as a primary defence mechanism against salinity. When exposed to natural soils, plants produced more leaves and flowers, with lower flower abortion rates than plants in a sterile substrate, and the stimulated plants displayed faster responses across time before reaching a plateau, while the recovery increased with time. Our results highlight the need for integrative and multidisciplinary approaches to understand plant-abiotic stress-microorganisms interactions. In M. pudica, soil microorganisms had weak or no effects on biomass or biochemical stress markers; however, their presence strongly improved reproductive traits and seismonasty, thus facilitating potential plant establishment in a new environment.

Effects of High Salinity and Water Stress on Wetland Grasses from the Spanish Mediterranean Coast.

The impacts of climate change are reaching unprecedented levels, heightening the risk of species loss and ecosystem service degradation. Wetlands, highly threatened ecosystems, serve vital ecological functions by capturing carbon, filtering water, and harbouring diverse wildlife. Coastal wetlands encounter many challenges, such as increased drought periods and escalating salinity levels, severely impacting plant biodiversity. Assessing how plants respond to various environmental stress factors is imperative for devising successful conservation strategies. In the present study, we examined three representative grass species found in various habitats within the Albufera Natural Park, close to the city of Valencia on the Spanish Mediterranean coast: Imperata cylindrica, Phragmites australis, and Saccharum ravennae. High salinity and water stress conditions were induced by subjecting the plants to irrigation with solutions containing 200, 400, 600, and 800 mM NaCl or withholding irrigation altogether to mimic coastal flooding and drought scenarios. The treatments were maintained until noticeable wilting of the plants occurred, at which point a range of stress biomarkers were determined, including photosynthetic pigments, ions, osmolytes, oxidative stress markers, and antioxidant metabolites, as well as antioxidant enzyme activities. Saccharum ravennae displayed the highest sensitivity to salt stress, whereas I. cylindrica appeared to be the most tolerant. The primary salinity tolerance mechanism observed in I. cylindrica and P. australis was a blockage of ion transport from the root zone to the aerial part, together with the salt-induced accumulation of proline and soluble sugars to high concentrations in the former. No significant effects of the water deficit treatment on the growth or biochemical parameters were observed for any of the analysed species. These findings offer valuable information for the effective management and conservation of coastal wetlands facing the challenges posed by climate change.