Bio-Stimulating Effect of Natural Polysaccharides from Lobularia maritima on Durum Wheat Seedlings: Improved Plant Growth, Salt Stress Tolerance by Modulating Biochemical Responses and Ion Homeostasis

Abstract

Bioactivities of polysaccharides derived from halophyte plants have gained attention in recent years. The use of biostimulants in agriculture is an innovative method of dealing with environmental stressors affecting plant growth and development. Here, we investigated the use of natural polysaccharides derived from the halophyte plant Lobularia maritima (PSLm) as a biostimulant in durum wheat seedlings under salt stress. Treatment with polysaccharide extract (0.5, 1, and 2 mg/mL PSLm) stimulated in vitro wheat growth, including germination, shoot length, root length, and fresh weight. PSLm at 2 mg/mL provided tolerance to plants against NaCl stress with improved membrane stability and low electrolyte leakage, increased antioxidant activities (catalase (CAT), peroxidase (POD), and superoxide dismutase (SOD)), enhanced leaf chlorophyll fluorescence, proline, and total sugar contents, decreased lipid peroxidation (MDA), and reactive oxygen species (H2O2) levels, and coordinated the efflux and compartmentation of intracellular ions. The expression profile analyses of ten stress-related genes (NHX1, HKT1.4, SOS1, SOD, CAT, GA20-ox1, GA3-ox1, NRT1.1, NRT2.1, and GS) using RT-qPCR revealed the induction of several key genes in durum wheat growing in media supplemented with PSLm extract, even in unstressed conditions that could be related to the observed tolerance. This study revealed that PSLm extract contributes to salt tolerance in durum wheat seedlings, thereby enhancing their reactive oxygen species scavenging ability, and provided evidence for exploring PSLm as a plant biostimulant for sustainable and organic agriculture.