A pot-controlled watering approach was employed to reveal the effect of soil water stress on photosynthetic physiology of Paspalum notatum Flugge under special climatic conditions in arid-hot valley region. Four treatments were set up: control (CK), low stress (LS), moderate stress (MS), and high stress (HS). Physiological measurements were taken to assess indices such as absolute plant height, canopy area, leaf area, leaf water content, and leaf water potential. Additionally, photosynthetic parameters were measured, including net photosynthetic rate, intercellular CO2 concentration, stomatal conductance and chlorophyll fluorescence. The results indicate that under water stress, as the duration of stress increases, the growth of Paspalum notatum Flugge was inhibited, the water available in the body of Paspalum notatum Flugge gradually decreased. Photosynthesis was inhibited and PS II reaction center was disrupted to some extent. To improve water retention, Paspalum notatum Flugge initiated self-protective mechanisms, diminishing leaf water potential and enhancing ability to absorb water from the soil. In the meantime, Paspalum notatum Flugge adjusted to adversity by reducing the stomatal aperture to inhibit water loss, lowering Tr, and increasing WUE. The experiment showed that after rehydration, damaged photosynthetic apparatus of Paspalum notatum Flugge retained a certain self-recovery capability. This phenomenon suggests the reversible deactivation of the photosynthetic apparatus in response to water stress.

Lawns play a key role in enhancing public spaces, preventing soil erosion, and acting as barriers against dust and sludge. In Brazil, Paspalum notatum is widely cultivated for its adaptability to the country's ecosystems and the availability of native ecotypes. However, soil salinization, a growing ecological concern, can limit lawn growth due to sodium and chloride ion toxicity. This study aimed to identify the most tolerant among five genotypes (Arua & iacute; and Tiriba cultivars, BRA 010006 and BRA 019178 accessions and the commercial species Axonopus fissifolius) subjected to salinity levels (0.5, 1.5, 3.0, 4.5, and 6.0 dS m(-1)). Analyzed variables included Na and Cl contents in plants, growth parameters (leaf and root dry mass and soil coverage), and morphological symptoms. No significant changes in leaf color or damage compromising aesthetics or functionality at salinity levels from 0.5 to 1.5 dS m(-1), with only occasional yellowing or minor scorch. Higher salinity led to leaf burn and yellowing, particularly in accession BRA 010006 and the control. Sodium and chloride contents, especially sodium, was higher in roots than leaves. Accession BRA 019178, followed by cultivars Arua & iacute; and Tiriba, demonstrated moderate tolerance, maintaining satisfactory soil coverage and dry mass across the tested salinity levels. These findings highlight the importance of selecting native turfgrasses with enhanced salt tolerance for landscaping applications in saline-prone areas.