Abstract: (27 Views)
Salicornia persica is a promising halophyte for sustainable agriculture in saline and arid regions, providing forage, seed oil, and edible shoots. The germination stage is highly sensitive to salinity and drought, which often co-occur in coastal and inland saline ecosystems. Zanjan Province, characterized by a cold semi-arid climate, 200–300 mm annual rainfall, severe winters, and increasing river salinity, poses particular challenges for establishing Salicornia. Successful cultivation depends on identifying tolerant ecotypes and optimizing early-stage irrigation. Previous studies mostly examined salinity or drought separately, leaving the combined effects on Iranian ecotypes underexplored. This study aimed to evaluate the interactive effects of four irrigation water salinity levels (control ≈0.5, 10, 30, and 50 dS/m) and three field capacity levels (100%, 75%, 50%) on germination percentage, germination rate, seedling growth, and stress physiology of three native ecotypes (Central, Gorgan, Bushehr) under controlled greenhouse conditions. Secondary objectives included identifying critical stress thresholds, ranking ecotype tolerance, generating a germination heatmap, and proposing practical irrigation protocols.
Materials and Methods
The experiment was conducted in a research greenhouse in Zanjan (UTM Zone 39, E: 269962 m, N: 40680674 m) as a factorial experiment in a completely randomized design with three replicates. Treatments comprised four salinity levels, prepared by dissolving NaCl in distilled water and verified using an EC meter, and three water regimes based on pot weight. Seeds of S. persica were collected from native habitats (Central: Iranian Plateau; Gorgan: Caspian coast; Bushehr: Persian Gulf coast), cleaned, and surface-sterilized with 1% sodium hypochlorite. Fifty seeds (~0.1–0.13 g) were sown in 5-kg plastic pots filled with loamy soil (field capacity = 1300 g water). Pots were arranged in three lines (one ecotype per line), totaling 108 pots. Irrigation was applied daily to maintain target weights (100% FC: 1300 g; 75% FC: 975 g; 50% FC: 650 g). Germination was recorded daily for 14 days. The germination rate index (GRI) was calculated using Maguire’s formula. Root and shoot lengths were measured. Proline (Bates method), glycine betaine (Grieve & Grattan), SOD and CAT activities (spectrophotometry), and total protein (Bradford method) were quantified from fresh leaf samples. A germination heatmap was generated using Python 3.11. Statistical analyses, including Two-Way ANOVA, Tukey’s HSD, linear regression, and PCA, were performed in SPSS 26.
Results
Two-Way ANOVA revealed highly significant effects of salinity (F>150), field capacity (F=123.89), and their interaction (F=14.27) on germination percentage (p<0.001). Under optimal conditions (control water + 100% FC), Bushehr, Gorgan, and Central achieved 95%, 85%, and ~85% germination, respectively. At 50 dS/m with full irrigation, germination dropped to 25%, ~15%, and ~15%, respectively. Reducing irrigation amplified salinity stress. At 50 dS/m + 50% FC, Bushehr retained 15%, Gorgan ~8%, and Central near 0%. Tukey’s test confirmed significant differences among all salinity and irrigation levels (p<0.001). Linear regression indicated that each 1 dS/m increase in salinity reduced germination by 1.27%, and each 1% decrease in soil moisture reduced it by 0.34%. The Bushehr ecotype showed a positive and significant coefficient, reflecting its superior tolerance. Seedling growth decreased under severe stress, while osmolyte accumulation and antioxidant enzyme activities increased, especially in Bushehr, demonstrating robust stress defense. Proline increased from 5 to 15 μmol/g FW, glycine betaine from 6 to 18 μmol/g FW, SOD from 100 to 120 units, and CAT from 80 to 100 units. The heatmap illustrated a gradual decline in germination from 95% (red) to ~0% (dark green). PCA explained 64.9% of variance along PC1 (salinity–germination trade-off) and 33.3% along PC2 (moisture effect), with Bushehr clustering in the high-germination zone and Central in the low-germination zone.
Conclusion
Combined salinity and drought exert a synergistic negative effect on Salicornia germination. Bushehr showed the highest tolerance, Central the greatest sensitivity, and Gorgan intermediate performance. For successful cultivation in saline and water-limited areas like Zanjan, Bushehr is recommended, with full irrigation (100% FC) and low-salinity water (<10 dS/m) during the first 10–14 days. After establishment, plants tolerate up to 50 dS/m and 50% FC. These findings provide a scientific foundation for ecotype selection, irrigation management, and breeding programs aimed at sustainable cultivation and rehabilitation of saline lands.
Materials and Methods
The experiment was conducted in a research greenhouse in Zanjan (UTM Zone 39, E: 269962 m, N: 40680674 m) as a factorial experiment in a completely randomized design with three replicates. Treatments comprised four salinity levels, prepared by dissolving NaCl in distilled water and verified using an EC meter, and three water regimes based on pot weight. Seeds of S. persica were collected from native habitats (Central: Iranian Plateau; Gorgan: Caspian coast; Bushehr: Persian Gulf coast), cleaned, and surface-sterilized with 1% sodium hypochlorite. Fifty seeds (~0.1–0.13 g) were sown in 5-kg plastic pots filled with loamy soil (field capacity = 1300 g water). Pots were arranged in three lines (one ecotype per line), totaling 108 pots. Irrigation was applied daily to maintain target weights (100% FC: 1300 g; 75% FC: 975 g; 50% FC: 650 g). Germination was recorded daily for 14 days. The germination rate index (GRI) was calculated using Maguire’s formula. Root and shoot lengths were measured. Proline (Bates method), glycine betaine (Grieve & Grattan), SOD and CAT activities (spectrophotometry), and total protein (Bradford method) were quantified from fresh leaf samples. A germination heatmap was generated using Python 3.11. Statistical analyses, including Two-Way ANOVA, Tukey’s HSD, linear regression, and PCA, were performed in SPSS 26.
Results
Two-Way ANOVA revealed highly significant effects of salinity (F>150), field capacity (F=123.89), and their interaction (F=14.27) on germination percentage (p<0.001). Under optimal conditions (control water + 100% FC), Bushehr, Gorgan, and Central achieved 95%, 85%, and ~85% germination, respectively. At 50 dS/m with full irrigation, germination dropped to 25%, ~15%, and ~15%, respectively. Reducing irrigation amplified salinity stress. At 50 dS/m + 50% FC, Bushehr retained 15%, Gorgan ~8%, and Central near 0%. Tukey’s test confirmed significant differences among all salinity and irrigation levels (p<0.001). Linear regression indicated that each 1 dS/m increase in salinity reduced germination by 1.27%, and each 1% decrease in soil moisture reduced it by 0.34%. The Bushehr ecotype showed a positive and significant coefficient, reflecting its superior tolerance. Seedling growth decreased under severe stress, while osmolyte accumulation and antioxidant enzyme activities increased, especially in Bushehr, demonstrating robust stress defense. Proline increased from 5 to 15 μmol/g FW, glycine betaine from 6 to 18 μmol/g FW, SOD from 100 to 120 units, and CAT from 80 to 100 units. The heatmap illustrated a gradual decline in germination from 95% (red) to ~0% (dark green). PCA explained 64.9% of variance along PC1 (salinity–germination trade-off) and 33.3% along PC2 (moisture effect), with Bushehr clustering in the high-germination zone and Central in the low-germination zone.
Conclusion
Combined salinity and drought exert a synergistic negative effect on Salicornia germination. Bushehr showed the highest tolerance, Central the greatest sensitivity, and Gorgan intermediate performance. For successful cultivation in saline and water-limited areas like Zanjan, Bushehr is recommended, with full irrigation (100% FC) and low-salinity water (<10 dS/m) during the first 10–14 days. After establishment, plants tolerate up to 50 dS/m and 50% FC. These findings provide a scientific foundation for ecotype selection, irrigation management, and breeding programs aimed at sustainable cultivation and rehabilitation of saline lands.
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