Contrasting Morphological, Physiological, Biochemical, and Ionic Responses of Lolium perenne to Drought and Salinity Stress

Drought and salinity are major abiotic stresses limiting plant performance in managed and natural ecosystems, including turfgrass systems. This study investigated the morphological, physiological, biochemical, and ionic responses of three Lolium perenne cultivars grown in natural and sterile soils under controlled water deficit and salinity treatments. Both stresses significantly reduced plant growth, but their underlying drivers differed markedly. Drought primarily imposed osmotic limitation, affecting biomass accumulation and plant water status, whereas salinity introduced an additional ionic constraint characterized by substantial Na+ and Cl− accumulation and reduced K+/Na+ ratios. This ionic imbalance was associated with enhanced oxidative stress and greater destabilization of photosynthetic pigments relative to drought. Multivariate hierarchical clustering revealed distinct trait coordination patterns under the two stress types, highlighting tighter integration among ionic regulation, redox balance, and growth limitation under salinity. Across treatments, plants grown in natural soil generally maintained improved physiological performance compared with those in sterile soil, although soil effects modulated response magnitude rather than direction. Cultivar-dependent differences reflected variation in regulatory efficiency across traits. Overall, the findings demonstrate that drought and salinity induce fundamentally different stress hierarchies in L. perenne, emphasizing the central role of ionic homeostasis in salinity tolerance and the value of integrated trait analysis for turfgrass stress management.