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Hydraulic and tissue adjustments enable the maintenance of mangrove seedling growth under increasing salinity
  • Vanessa Negrão-Rodrigues
Vanessa Negrão-Rodrigues
Museu Paraense Emilio Goeldi Campus de Pesquisa
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Abstract

An increase in salinity is one of the environmental conditions that will have the greatest impact on mangroves in coming decades. However, little is known about the ability of mangrove seedlings to maintain their growth and physiological adaptation to salinization over time. Here, we examined the impact of salinity increase duration on the growth, hydraulic properties, and tissue characteristics of seedlings of two mangrove species, Avicennia germinans and Rhizophora racemosa. We observed that the salinity increase had minimal impact on plant’s growth, possibly due seedlings capacity for acclimation, as both species demonstrated coordinated adjustments to salinity in traits such as HSM, Ψ PD, Ψ MD, Ψ s e Ψ tlp. However, the two species exhibited distinct strategies, with R. racemosa showing a more conservative behavior, while A. germinans adopting a riskier strategy. After three months of exposure to the salinity gradient, osmotic adjustments of the species did not persist. This discontinuity could represent a risk to the maintenance of growth and survival of the species over extended periods. Therefore, our results demonstrated the ability of mangrove seedlings to physiologically acclimate and sustain their growth in the presence of increasing salinity. They also raised concerns regarding the prolonged exposure to higher salinity concentrations.