Excessive use of chemical fertilizers to ensure food security amid population growth, global climate change, extreme weather conditions, drought, overexploitation of freshwater resources, an‎d lan‎d degradation has created severe challenges for sustainable agricultural production. Corrective approaches provide insights into salt stress tolerance reported in some crops such as rice an‎d wheat. Meanwhile, advances in algal research have shown that algal polysaccharides can be utilized for various ecosystem agricultural services. Due to their photosynthetic efficiency an‎d higher growth rates compared to terrestrial plants, algae are considered efficient bioresources for biomass an‎d phytochemical production. The potential of algal polysaccharides for producing biochar (hereafter referred to as "phycochar" due to its algal origin), its elemental composition, an‎d its role in bioremediation have been discussed. In this study, the effects of biotic an‎d abiotic stresses on plants were first addressed, such as salt stress, which reduces plant growth an‎d causes nutrient deficiencies around the roots. Then, the plant responses to salt stress an‎d its impacts on plant physiology, biochemistry, an‎d metabolism were discussed. The mechanisms by which salt-tolerant plants cope with this stress were also examined, highlighting numerous physiological an‎d biochemical responses of plants to salt stress. This work initially covers the preparation of BBM culture medium an‎d cultivation of the microalga Scenedesmus sp., followed by the extraction an‎d isolation methods of polysaccharides from the algae. Cultivation of this alga resulted in significant biomass production. Subsequently, biochemical characterization methods of the extracted polysaccharides demonstrated that they can help reduce oxidative stress an‎d maintain cellular health in rice plants under both salt stress an‎d non-stress conditions by increasing antioxidant enzyme levels an‎d improving potassium uptake. The presence of sulfate groups in the polysaccharides is of particular importance, as sulfated polysaccharides are known for their biological activities, including antioxidant an‎d anti-inflammatory properties. This study emphasized the importance of sulfate content in enhancing the functional properties of extracted polysaccharides for potential applications in food, pharmaceutical, an‎d agricultural fields. The sulfate content in the extracted polysaccharides was 19.34%. In this research, the salt stress tolerance threshold of rice plants was determined, showing that different salt concentrations (especially 250 mM) had a significant effect on rice growth parameters. With increasing salt concentration, a substantial reduction was observed in growth parameters such as fresh an‎d dry weight of roots an‎d shoots by 40%, an‎d shoot an‎d root length by 10%. Addition of polysaccharides extracted from Scenedesmus sp. to rice plants led to a significant increase in shoot an‎d root length under salt stress conditions. Furthermore, this study showed an increased potassium-to-sodium ion ratio in rice plants under both salt stress an‎d non-stress conditions.

مجيد طالبي , علي حسيني تفرشي

بدرالدين ابراهيم سيدطباطبايي

ابوذر سورني , پرويز احسان زاده