Assessing growth, physiological, and yield responses of eggplant (Solanum melongena L.) to salinity stress in controlled and field environments

Salinity is a major abiotic stress affecting agricultural productivity, particularly in arid and semi-arid regions. Environmental conditions play a critical role in shaping plant responses to salinity stress, potentially alleviating or intensifying its adverse effects. This study evaluated the impact of different environmental conditions and salinity levels on key morpho-physiological and yield traits of eggplant (Solanum melongena L.). The experiment was conducted using a two-factorial completely randomized design (CRD) with four environments—Net house, Greenhouse with white LED, Greenhouse with red LED, and Open Field (control)—and four salinity treatments with electrical conductivity (EC) levels of 2, 3, 4, and 5 dS/m (denoted as S1, S2, S3, and S4, respectively). Eighteen parameters were measured, including plant height, chlorophyll content, NDVI, fruit weight, and fruit yield. Overall, increasing salinity reduced plant growth, pigment content, and yield, whereas controlled environments—especially greenhouses with supplemental lighting—significantly improved performance compared to the open field. ANOVA indicated significant effects (p ≤ 0.01) of both salinity and environment on most traits. The highest fruit weight (400.25 g/plant) and yield (1.345 kg/plant) were obtained in the Net house at S1, while the lowest (241 g/plant and 0.988 kg/plant) occurred in the Open Field at S4. Plant height followed a similar trend, with the tallest plants (73.66 cm) recorded in the Net house at S1 and the shortest (57.79 cm) in the Open Field at S4. Chlorophyll content (SPAD) and NDVI decreased with higher salinity, while total chlorophyll content peaked in the Greenhouse with red LED (2.71 mg/g) and reached its lowest at S4 (1.51 mg/g). These results highlight that optimized environmental management, particularly in controlled conditions, can substantially alleviate the negative effects of salinity stress on eggplant growth and productivity.