Integrated Physiological and Ornamental Responses of Cestrum nocturnum to Salinity Stress: Identifying Tolerance Thresholds Under Saline Irrigation

ABSTRACT

The use of saline water for irrigation is an increasingly important strategy to reduce freshwater consumption in ornamental horticulture; however, the tolerance and physiological responses of many species remain poorly understood. This study provides the first comprehensive assessment of the response of Cestrum nocturnum to saline irrigation under nursery conditions, integrating physiological, nutritional, and ornamental quality parameters. Plants were subjected to three salinity levels (2.1, 4.7, and 7.2 dS m ⁻¹ ) over a 10‐week period. The results reveal that C. nocturnum activates early adaptive mechanisms, including stomatal regulation and changes in leaf hydraulic function, in response to salinity. A key finding is the identification of a threshold response: moderate salinity (4.7 dS m ⁻¹ ) caused only minor reductions in biomass with limited impact on plant quality, whereas high salinity (7.2 dS m ⁻¹ ) led to severe photochemical stress, ion toxicity (Na and Cl accumulation), chlorosis, necrosis, and a strong decline in growth and ornamental value. By linking physiological processes with commercial quality traits, this study fills a critical knowledge gap and establishes practical salinity limits for this species. These results support the use of moderately saline water in C. nocturnum production while defining the thresholds beyond which plant performance is compromised.