Physiological responses of date palm (Phoenix dactylifera) seedlings to seawater and flooding.

Baoguo Du,Yuhua Ma,Gadah Albasher,Rainer Hedrich,Philip J White,Heinz Rennenberg,Lukas Fasbender,Ana Maria Yáñez‐Serrano,Christiane Werner,Saleh Alfarraj,Leila Arab

doi:10.1111/nph.17123

Abstract

In their natural environment along coast lines, date palms are exposed to seawater inundation and, hence, combined stress by salinity and flooding. To elucidate the consequences of this combined stress on foliar gas exchange and metabolite abundances in leaves and roots, date palm seedlings were exposed to flooding with seawater and its major constituents under controlled conditions. Seawater flooding significantly reduced CO2 assimilation, transpiration and stomatal conductance, but did not affect isoprene emission. A similar effect was observed upon NaCl exposure. By contrast, flooding with distilled water or MgSO4 did not affect CO2 /H2 O gas exchange or stomatal conductance significantly, indicating that neither flooding itself, nor seawater sulfate, contributed greatly to stomatal closure. Seawater exposure increased Na and Cl contents in leaves and roots, but did not affect sulfate contents significantly. Metabolite analyses revealed reduced abundances of foliar compatible solutes, such as sugars and sugar alcohols, whereas nitrogen compounds accumulated in roots. Reduced transpiration upon seawater exposure may contribute to controlling the movement of toxic ions to leaves and, therefore, can be seen as a mechanism to cope with salinity. The present results indicate that date palm seedlings are tolerant towards seawater exposure to some extent, and highly tolerant to flooding.

Highlights

Different plant species are highly variable with respect to their responses to salt stress
In the first set of experiments, date palm seedlings were exposed to seawater flooding
Compared with controls receiving distilled water, assimilation declined to 37% from 7.6 to 2.7 μmol CO2 m−2 s−1, transpiration to 36% from 1.6 to 0.6 mmol H2O m−2 s−1, and stomatal conductance to 28% from 64.2 to 18.0 mmol H2O m−2 s−1, whereas dark respiration was maintained at −0.5 μmol CO2 m−2 s−1

Summary

Introduction

Different plant species are highly variable with respect to their responses to salt stress. According to their tolerance, plants are divided into glycophytes and halophytes. Glycophytes are highly susceptible to salt stress, whereas halophytes can grow at high concentrations of salt in their environment (Acosta-Motos et al, 2017; White et al, 2017; Van Zelm et al, 2020). Molecular pathways underlying salt-adaptation mechanisms have been dissected and partially identified in some plant species, the mechanisms that mediate salt tolerance of date palms are still largely unknown (Yaish & Kumar, 2015; Al Kharusi et al, 2017; Hazzouri et al, 2020)

Methods

Results

Discussion

Conclusion