Morphological, Biochemical, and Metabolomic Strategies of the Date Palm (Phoenix dactylifera L., cv. Deglet Nour) Roots Response to Salt Stress

Safa Bouhouch,Ali Chenari Bouket,Tomasz Oszako,Manal Eshelli,Houda Ben Slama,Mostafa E Rateb,Adam Okorski,Lassaad Belbahri

doi:10.3390/agronomy11122389

Abstract

Numerous Tunisian arid and semi-arid regions are subjected to soil salinity. Thus, they are known for halophytes plants cultivation, including date palms. Phoenix dactylifera L., cv. ‘Deglet Nour’, is a valuable Tunisian cultivar subjected to high salinity levels. In this way, our purpose is to evaluate the response of its roots to long period exposition to increasing salt concentrations. We started by studying the effects of 4 g/L, 8 g/L, 12 g/L, and 16 g/L NaCl on the parameters of germination (Growth rate—GR, Seed Mortality Rate—SLM, Germination Mean Time—GMT, and Germination Speed—GS) of date palm seeds for a 2-month period. We found that 4 g/L NaCl did not affect the seeds germination, and, hereinafter, the parameters of germination and the radicle length decreased with the increase of NaCl concentrations and experiment time. Then, we demonstrated a high antioxidative enzymes CAT and SOD production in case of salt stress augmentation. Lastly, a metabolomic approach was carried out by LC-HRMS, followed by an untargeted and targeted analysis using the XCMS online and MZmine tools, respectively. The roots chemical composition was compared using PCA. We identified 25 secondary metabolites, divided into 3 categories. Metabolites known for their role in salt stress alleviation include δ-tocotrienol, metabolites identified in salt stress for the first time, and other unknown metabolites.

Highlights

Soil salinization is becoming a major problem in multiple regions around the world
The germination rate is determined throughout the following formula [30]: Germination Rate (GR) = n1/d1 + n2/d2 +
The percentage of seeds germination dropped at 8 g/L, 12 g/L, and 16 g/L concentrations in the 20th and 40th day of germination compared to the Control and raised again from the 40th day, reaching up to

Summary

Introduction

Soil salinization is becoming a major problem in multiple regions around the world. It is affected by numerous factors, including climate changes and uncontrolled anthropogenic activities by the continuously increasing human population [1,2]. Harsh arid and semi-arid regions are generally exposed to multiple other stress factors accentuating the salinity stress, such as drought and extreme temperatures [7,8]. These regions are distinguished by the culture and development of halophytic plants. These plants are known for their ability to cope with high salt concentrations (>400 mM) due to their mechanisms of salt accumulation and exclusion, limitation of transpiration, ionic adjustment, antioxidant mechanisms activation, and expression of secondary metabolites responsible for salt stress mitigation [9,10,11]

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