Salinity Tolerance in Fraxinus angustifolia Vahl.: Seed Emergence in Field and Germination Trials

Abstract

The effect of salinity on seed germination/emergence in narrow-leaved ash (Fraxinus angustifolia) was studied both under field and laboratory conditions, in order to detect critical values to NaCl exposure. Research Highlights: Novel statistical methods in germination ecology has been applied (i) to determine the effects of chilling length and salinity (up to 150 mM NaCl) on Fraxinus angustifolia subsp. oxycarpa seed emergence, and (ii) to estimate threshold limits treating germination response to salinity as a biomarker. Background and Objectives: Salinity cut values at germination stage had relevant interest for conservation and restoration aims of Mediterranean floodplain forests in coastal areas subjected to salt spray exposure and/or saline water introgression. Results: Salinity linearly decreased germination/emergence both in the field and laboratory tests. Absence of germination was observed at 60 mM NaCl in the field (70-84 mM NaCl depending on interpolation model) and at 150 mM NaCl for 4-week (but not for 24-week) chilling. At 50 mM NaCl, germination percentage was 50% (or 80%) of control for 4-week (or 24-week) chilling. Critical values for salinity were estimated between freshwater and 50 (75) mM NaCl for 4-week (24-week) chilling by Bayesian analysis. After 7-week freshwater recovery, critical cut-off values included all tested salinity levels up to 150 mM NaCl, indicating a marked resumption of seedling emergence. Conclusions: Fraxinus angustifolia is able to germinate at low salinity and to tolerate temporarily moderate salinity conditions for about two months. Prolonged chilling widened salinity tolerance.Forests 2019, 10, 940 2 of 18 and late (2100) century [22]. The global conservation awareness for these ecosystems-which nowadays resulted in a protected status under the international biodiversity-related multilateral environmental agreements [23] for more than one third of swamps, flooded forests and coastal wetlands-might not be sufficient to prevent degradation risks arisen from interactions with large-scale processes, land-use changes and agricultural land-use intensification. Consequently, undertaking practice and policy actions to prevent wetland degradation and loss remains a focus of international processes, such as the Convention on Biological Diversity (CBD) Aichi Targets and the United Nations (UN) Sustainable Development Goals (SDGs). In coastal floodplains, human pressure, altered water flows, contaminants from internal urban and agricultural lands, and increased soil salinity [24][25][26] were particularly relevant, and science-based management options should be urgent [27] to face adverse climate-related impacts exacerbated by increasing human-induced pressures [28][29][30].F. angustifolia coastal alluvial forests were mainly judged under unfavorable (habitat 91F0) or inadeguate (habitat 91E0 * ) states, following the 2007-2012 EU Habitat Directive Art. 17 assessment [31]. The major threats to this species were currently considered to be high fragmentation with connectivity loss a...

The Impact of Biotic and Abiotic Stress Factors on Development of European Ash Tissue Cultures

“…We showed that both seedlings and callus of ash are able to develop during slight/medium (not exceeding 0.5% or 1.0%) salt stress. Our results are in agreement with Raddi et al [60] who showed that F. angustifolia (Vahl.) is able to germinate at low salinity and to tolerate temporarily moderate salinity (not exceeding 75 mM NaCl) conditions.…”

“…Ultimately, the plant becomes resistant to abiotic factors [63,64]. Under environmental stress, photorespiration acts as an energy sink, preventing excessive reduction of the photosynthetic electron transport chain and photoinhibition, as well as preventing the accumulation of ROS [60,65]. Peroxidases in general are involved in multiple metabolic processes during the entire life cycle of plants, including the metabolism of ROS, reactive nitrogen species (RNS) and metabolism of phytohormones (e.g., auxins), as well as in the production of lignin and suberin, and in cross-linking of cell wall components [41,42,66].…”

Salinity-induced changes in the morphology, physiology, and anatomy of seeds and seedlings of smooth narra (Pterocarpus indicus Willd. f. indicus)

“…However, the percent survival under this treatment was considerably low compared to other treatments. This response is the same as in the numerous plant species affected by salinity stress during germination (e.g., Katembe et al 1998;Ghazy et al 2009;Liu et al 2010;Raddi et al 2019). In the study of Fang et al (2006), there was a significant reduction in the seedling survival with increase in NaCl concentration after 50 days of treatment.…”