Effects of Proline and Seaweed on Growth Parametres and of Green Onion Cultivation under Greenhouse Conditions

This study was conducted to investigate the effects of proline (PR), an amino acid, and seaweed (SW), which has biostimulant properties, on the growth and development of green onion (Allium cepa L.) plants. The experiment was conducted in an unheated glass greenhouse at Van Yüzüncü Yıl University using a randomized block experimental design. Key growth parameters including plant height, root length, stem diameter, number of leaves, total fresh and dry weight, and SPAD value were assessed. The results revealed that the highest plant height (29.24 cm) was recorded in the PR2+ SW1 (100 ppm proline + 3 g/L seaweed) treatment, demonstrating a significant synergistic effect compared to individual applications (p < 0.001). The longest root length was observed in the PR1+ SW2 (50 ppm proline + 5 g/L seaweed) treatment (17.02 cm), suggesting enhanced root development. The highest stem diameter (5.40 mm) was measured in the SW2 (5 g/L seaweed) treatment. Regarding biomass accumulation, the PR1+ SW2 treatment resulted in the highest total fresh weight (172.67 g), while the control group had the lowest (144.00 g). The highest dry weight (22.91 g) was recorded in the PR2+ SW1 treatment. For chlorophyll content, the PR2+ SW1 treatment yielded the highest SPAD value (69.53), though the differences were not statistically significant (p = 0.1467). These findings suggest that proline and seaweed applications can enhance growth and yield in green onion production, with the PR2+ SW1 combination providing the most favorable results. However, further studies are needed to determine the optimal application rates, assess their effectiveness under different environmental conditions, and evaluate their long-term impact on agricultural production.