Salinity is a major constraint for lettuce production, affecting plant growth, physiological status, and market quality. This study evaluated the combined effects of increasing salinity levels (S0: non-saline control; S30, S60, and S120 mM NaCl) and Trichoderma harzianum inoculation on morphological, physiological, and quality-related traits of lettuce. Increasing salinity levels resulted in significant reductions in growth-related parameters, particularly leaf area, shoot biomass, root volume, and cutting resistance (CR), with the most pronounced decreases observed at S120. In contrast, several physiological and quality-related parameters showed different response patterns. Membrane stability index (MSI) and chlorophyll index remained relatively stable across salinity treatments, while total soluble solids (C) increased with increasing salinity, indicating osmotic adjustment under stress conditions. Leaf color parameters showed reductions in lightness and chroma at higher salinity levels, suggesting structural and optical changes in leaves rather than severe pigment degradation. The effects of Trichoderma on plant growth were limited and did not consistently mitigate growth reductions under salinity. However, inoculation influenced several physiological and quality-related traits, including MSI and TSS, indicating a role in physiological regulation and stress adaptation rather than direct growth promotion. Multivariate analyses indicated that salinity was the main factor contributing to treatment separation, whereas Trichoderma application influenced the overall trait profile without consistently increasing growth parameters. Overall, the results suggest that under saline conditions, Trichoderma may contribute to stress tolerance and physiological stability rather than directly increasing plant growth, and its effectiveness depends on stress severity.
Güvenaltın et al. (Fri,) studied this question.