Effect of Salicylic Acid on some Morphological and Biochemical Traits of Rice (Oryza sativa L.) under salt stress

Rice is one of the important crops that is sensitive to salinity stress, especially in the early stages of growth. Today, the use of plant growth regulators such as salicylic acid has made plants resistant to environmental stresses such as salinity.The purpose of this research was to study the effect of salicylic acid application on some morphological and biochemical characteristics of rice plants under salt stress. For this purpose, factorial plant stabilization based on completely random design with 5 levels of salinity (0, 25, 50, 75, 100 mM sodium chloride) and 3 levels of salicylic acid (0, 0.5, 1 mM) was performed in 3 repetitions. The measured traits included germination percentage, length of shoot and root, amount of total protein, malondialdehyde, proline and activity of some antioxidant enzymes. The results of this research showed that salinity caused a significant decrease in germination percentage, stem and root length, and decreased protein activity, while in plants treated with salicylic acid, the amount of this reduction is moderated. The highest germination percentage was observed in control and 25mM salt stress treatment and decreased by increasing salt treatment up to 100 mM treatment. The highest shoot length observed in 25 mM salt with salicylic acid in 0.5 mM concentration. The highest and the lowest root length derived by 75mM salt stress with 1mM salicylic acid and 100 mM salt stress without any salicylic acid treatments respectively. Protein measurement in different treatment indicated that increasing of salt stress cause decreasing the leaf protein content especially in 100 mM salt concentration. In all salt treatments, salicylic acid increased the leaf protein content, and raising the salicylic acid from 0 to 1 mM cause increasing the leaf protein content. The highest leaf protein content was measured in without salt treatment with 1mM salicylic acid. Salt stress caused rising the malondialdehyde content in 100 mM salt treatment rather than other treatments, but salicylic acid application in 0.5 and 1 mM concentration decreased it. On the other hand, the increase in the amount of biochemical traits including proline, antioxidant enzyme (superoxide dismutase) shows the role of one millimolar salicylic acid consumption in increasing the tolerance of this plant against salt stress. While the salinity stress, the activity of malondialdehyde, the activity of the antioxidant enzyme (catalase) increased, the use of salicylic acid reduces the oxidative stress by reducing the activity of these traits, which increases the resistance of the plant under stress.