The effect of silicon application on some quantitative and qualitative characteristics of safflower (Carthamus tinctorius L.) under salinity stress

Background and Objectives: Salinity is one of the most important environmental abiotic stresses that limit the growth and production of plants. On the other hand, silicon (Si) is the second most abundant element in soil and reduces biotic and abiotic stresses in plants. By penetrating the stem and leaves, silicon strengthens the plant antioxidant system, while strengthening the physical organs and improving the plant physiological processes, which results in strengthening the antioxidant system of the plant and increasing its efficiency against environmental stresses. According to the recent findings of researchers, a small amount of silicon can affects the ability of plants to withstand salt stress. Oil seeds are important sources of vegetable oils. Safflower seed with an oil content of 25 to 45% is one of the most valuable oilseeds. The aim of this research was to evaluate the effect of silicon foliar application on some quantitative and qualitative characteristics of safflower under salt stress.

Materials and Methods: This experiment was conducted as a factorial based on a completely randomized design with three replications in greenhouse research of Nahavand Higher Education Complex during 2023. Experimental factors included salinity stress at three levels (0, 40 and 80 mM) and silicon foliar application at three levels (0, 2 and 4 g/L). The height of the plant, the stem diameter, the head diameter and weight, the 1000-grain weight, the percentage of the oil, and the amount and type of fatty acids were measured traits.

Results: The results of the experiment showed the positive effect of silicon application on most of the studied traits, so that the largest head diameter (14.70 mm) was created in the treatment of 4 g/L of silicon and without salt, which was not statistically different compared with the treatment of 4 g/L of silicon and 40 mM salinity. The highest amount of plant height, stem diameter, head weight and 1000-grain weight was obtained by applying 4 g/L silicon and 40 mM salinity stress. The increase percentage of these traits, compared to the non-application of silicon at the same salinity level (40 mM) was 18.11%, 15.19%, 14.78% and 17.35%, respectively. The highest percentage of oil (27.31%) was obtained by applying the highest level of silicon and salinity. The increase in the oil percentage in this treatment was 80.74% compared to the absence of silicone application at the same salinity level. The highest amount of linoleic acid (77.02%) was obtained in the treatment of 2 g/L silicon and 40 mM salinity. The increase percentage of linoleic acid in this treatment was 11.60% compared to the absence of silicon application at the same salinity level. The highest amount of oleic acid (18.90%) was produced using the highest level of silicon and no salinity. The highest level of stearic acid (2.80%) and linolenic acid (0.2%) was obtained in the control treatment.

Conclusion: The results of this research showed the positive effect of silicon application on most of the investigated traits. Also, with the application of silicon, the adverse effects of salt stress in some traits such as plant height, stem diameter, head weight, 1000-grain weight and oil percentage were reduced. Therefore, the use of silicon can be suggested as an effective method to reduce the destructive effects of salinity stress.