Improvement of Salt Tolerance and Nutrient Absorption in Pepper (Capsicum annum) Through Application of Salicylic Acid and Humic Acid

Document Type : Research Article


1 Horticultural Science

2 Yasooj Branch, Islamic Azad University


Introduction: Bell pepper (Capsicum annuum) belongs to solanaceae family, which is cultivated and consumed in the world due to its high economic value. Bell peppers also have valuable nutritional and medicinal compounds, including natural colors, antioxidants and vitamins A, B and E. Salinity stress is one of the most important environmental factors limiting growth, which has very adverse effects on plant growth and yield. Salinity stress reduced the yield of agricultural products due to the effect on the competitive absorption and transfer of nutrients in the plant. Nowadays, the increased tolerance of plants to environmental stresses from different pathways involve breeding programs and the use of plant growth regulators and organic substances. In comparison to breeding methods that are often long-term and cost-intensive, it is easy and inexpensive to use plant growth regulators such as Salicylic Acid (SA) and humic acid (HA). 
Material and Methods: To investigate the effect of Salicylic Acid (SA) and Humic Acid (HA) on the improvement of tolerance to salinity and absorption of mineral elements under salinity stress in greenhouse culture, a factorial experiment based on Randomized Complete Block Design (RCBD) was conducted in Yasooj. The first factor was SA in three levels (0, 1, and 2 mM), the second factors HA in two levels (0 and 5 g l-1), and the third factors salinity in three levels (0, 50, and 100 mM). The bell pepper seedlings cv. California were obtained from a commercial producer and planted in 4-liter plastic pots containing perlite and cocopeat (1:1) in 2015. Plants were grown in a hydroponic greenhouse with day/night temperature (24.3 and 15.4 oC) and 60 to 80% RH in the village of Nahrgah in Yasouj. After the plants were established (having about 4–5 leaves), sodium chloride salt was used in the concentrations of 0, 50, and 100 mmol in the nutrient solution for salinity stress. To prevent a sudden shock, the first one week all the pots were irrigated with a 10 mM-food solution and in the second week with a 25 mM salt solution. After that, the plants irrigated 50 and finally 100 mg of sodium chloride. Traits such as plant height, number of leaves, number of flowers, number of fruits, and average fruit weight, and yield, fresh and dry weight of leaf were measured. The content of K, Ca, Fe and Na elements in the leaves and roots of treated and untreated plants were measured by an atomic absorption device equipped with a graphite furnace system. Data analysis (ANOVA) was performed using MSTAT-C statistical software. The means were compared with the Tukey test (P≤ 0.05) and the graphs were plotted with Excel.
Results and Discussion: Results showed that the salinity has negative effects on growth factors. The application of HA and SA reduced the negative effects of salinity and increased growth parameters. The application of HA and Salicylic acid increased the number of pepper fruits under salt stress conditions. The highest number of fruits was obtained in the plants treated with 5 g l-1 HA and 2 mM salicylic acid compared to the other treatments. The results of this experiment showed that the application of HA and Salicylic acid had a significant effect on the content of mineral elements in the leaves and roots of sweet peppers under salt stress. The highest amount of Fe was observed in the leaves of pepper plants treated with 100 mM and the lowest in untreated plants. The highest amount of leaf calcium was obtained in peppers treated with SA 2 mM and HA 5 g l-1 in comparison to other treatments. Application of SA 1 and 2 mM increased the concentration of calcium of the leaves and roots of the pepper plant. The highest root potassium were obtained in plants treated with 5 g l-1 HA and 1mM SA at salinity level of 100 mM in comparison to the other treatments.
Conclusion: Salinity is an environmental factor limiting the production of crops in plants. According to the results of present study, it can be concluded that salinity reduced the growth parameters of the bell pepper plant. The use of SA and HA increased bell pepper tolerance to salinity and improved the vegetative and reproductive characteristics and absorption of mineral elements. Therefore, the application of HA 5 g l-1 and 2 mM SA is suggested to reduce the negative effects of salinity stress on bell pepper.


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