The Effects of Using Salicylic Acid and Silicon on Some Physiological ‎and Anatomical Indices in Two Ecotypes of Scrophularia striata L. ‎Medicinal Plant under Drought Stress

Today, water shortage is considered one of the main environmental challenges for plants, leading to metabolic and physiological disorders. It has attracted the attention of researchers in recent years. Salicylic acid (SA) and silicon (Si) are considered two drought stress modifiers in plants. To evaluate the drought stress on the physiological and anatomical index of Scrophularia striata for introduction in dry areas during 2020-2021, the present study was conducted as a factorial experiment based on a completely randomized design (CRD) with three replications at the University of Ilam. In this study, drought stress at two levels (50 and 100% of field capacity), SA at two levels (0 and 100 ppm), Si at two levels (0 and 1 g/L) on photosynthesis, gas exchange parameters, leaf relative moisture content, total protein, and anatomical indices were investigated. The results of this experiment showed that drought stress decreases relative leaf water content, total protein, photosynthesis, gas exchange parameters, and electrolyte leakage. Structurally, it caused a reduction in stomatal width, width of stomatal guard cells, stomatal density per unit area, and diameter of vascular tissues. Using SA and Si improved the photosynthesis, gas exchange parameters, relative moisture content, and total protein. In addition, the foliar application of SA and Si led to the improvement of the anatomical index caused by drought stress. The study results showed that drought stress had negative impacts on Scrophularia striata L, and using salicylic acid and silicon can improve drought stress tolerance in plants.