Abstract
Initiatives to restore natural ecosystems have had little success in arid and hyperarid ecosystems. In this context, the natural seedling establishment is particularly affected by drought patterns and climatic variability. Likewise, the effect of plant provenance on forest restoration success remains unclear, although previous studies have concluded that some seed locations might be better able to tolerate water stress. In this study, we examined the physiological mechanisms involved in the drought stress resistance of Prosopis tamarugo and Prosopis alba seedlings from different arid and hyperarid locations of the Atacama Desert in northern Chile. We measured the xylem water potential (Ψ), cuticular transpiration (Ec), specific leaf area (SLA) and pressure-volume curves at the intrapopulation and interpopulation levels of seedlings of both species subjected to three drought-induced treatments. In addition, plant characteristics such as seedling height (Sh), stem diameter (Sd), leaf biomass (Lb), root biomass (Rb) and seedling survival (Ss) were measured during the treatments. Seedlings of most hyperarid habitats had the highest values of Ψ and water content relative to the turgor loss point, as well as decreased SLA, especially during the strongest drought treatment. Ψ was strongly correlated with Sh in both species, and soil humidity was correlated with Sd. This study highlights the high variability of physiological responses to water stress in both species at the interpopulation and intrapopulation levels, which provides us with a powerful seed selection tool for future reforestation programmes aimed at the early selection and genetic improvement of species of the Prosopis genus.
Highlights
Drought stress in plants has been identified as a major limiting factor of growth and yield in arid and semiarid ecosystems
Significant differences occurred during the last measurement date, when the most aggressive drought treatment had already been applied
We analysed the effects of different drought treatments on seedlings of two phreatophyte Prosopis spp. which grow in hyperarid climate
Summary
Drought stress in plants has been identified as a major limiting factor of growth and yield in arid and semiarid ecosystems. Water stress caused by summer drought is the main factor limiting the establishment of this species (Villagra et al 2010). Other species tolerate drought stress based on a ‘water conservative strategy’ by avoiding water loss during dry and wet periods adjusting cuticular transpiration (Ec) and stomatal closure (Villar-Salvador et al 2004). Several authors agree that the main physiological drought adaptation strategy of arid climate plants seems to be the need to maintain a high water content and cell turgor, which might have a direct effect on their subsequent growth and seed production processes (López et al 2013; Villalobos and Peláez 2015). Under these same water limitations, the SLA of Erythrina velutina individuals—a member of the Fabaceae that can tolerate water stress—is significantly affected after long periods of drought stress (Da Silva et al 2010)
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