Plant microbial symbionts could play a significant role on root growth in hard soils, water availability to plants and soil physical and hydraulic properties by altering chemical composition of root exudates. So far little information is available linking the presence of endophyte in plants, with these phenomena and properties. We hypothesized that the presence of endophyte in plants may alter the root capability to penetrate into the hard soils, soil available water (SAW) and soil physical and hydraulic properties. Our results indicated that P. indica increased the maximum root growth pressure of maize and thereby stimulated the ability of roots to penetrate into the hard layers especially in the initial growth stages. Endophyte presence in both residues and aboveground parts of the tall fescue plants enhanced the soil organic carbon pools especially in the medium- and fine-textured soils and increased sub-critical water repellency in the rhizosphere soils. Therefore, it has a key role in the improvement of soil aggregate stability and physical quality. Moreover, the E+ grasses have more ability to absorb water at higher soil matric suctions due to drought tolerance mechanisms; therefore, actual integral energies were greater for E+ grasses rather than E? ones. Nevertheless, nominal integral energies were lower for the E+ plants. It means that water uptake in the nominal plant-available water range needs lower energy for the E+ plants. Finally, endophyte presence in the aboveground parts of the tall fescue plants can alleviate the adverse impacts of mechanical and drought stresses on plant water status and physiological characteristics, and improves the plant adaptions to these abiotic stresses. Keywords: Endophyte, Integral water capacity, Soil water repellency, Soil physical quality, Permanent wilting point, Mechanical stress.
