Background:
Spinacia oleracea, a nutrient-dense vegetable composed of 91% water, 4% starch, and 3% protein, is a staple in the Indian diet. However, salinity stress can hinder its growth. This study examines the effects of salinity on the morpho-biochemical traits of spinach in a hydroponic system.

Materials and methods:
Spinach seeds were sown on coco peat, and after 10 days, the seedlings were transferred to the hydroponic setup. The plants were treated with salt concentrations of ECe 0, 4.0, 6.0, 8.0, 10.0, and 12.0 ds/m, and various morpho-biochemical parameters were assessed at 10-day intervals.

Results:
In the control group, seed germination was 59.6 ± 1.45%, while increasing salt concentrations (4 to 10 dS/m) progressively reduced germination (50 ± 1.2% to 14 ± 2%). Root and shoot lengths (root: 14.16 ± 0.19 cm; shoot: 4.23 ± 0.28 cm at 4 dS/m), relative water content (47.5 ± 0.43% to 32.1 ± 0.86%), and leaf surface area (25.03 ± 0.26 to 9 ± 0.12 cm2) all declined with increasing salinity. Conversely, proline content (0.055 ± 0 to 0.12 ± 0 μg/ml) and antioxidant enzyme activity (SOD: 1.83±0.04/g protein; APX: 0.53 ± 0.1/mg protein; CAT: 0.0054 ± 0/mg protein) increased compared to the control. However, chlorophyll content (3.73 ± 0.02 to 1.95 ± 0.03 mg/g at 12 dS/m) and protein content (0.13 ± 0 at 4 dS/m to 0.054 ± 0 μg/ml at 12 dS/m) decreased with rising salinity.

Conclusions:
Therefore, it is concluded that spinach grown hydroponically can tolerate salt stress up to ECe 6.0 dS/m after 30 days of treatments, and more increased (8.0 to 12 dS/m) salt concentration that adversely affects overall morpho-biochemical performance.