Morphological and Physiological Responses of Euonymus (Euonymus japonicas) to Exogenous Paclobutrazol under Salinity Stress

Paclobutrazol (PBZ) is one of the most important triazole compounds. This compound increases plant tolerance to environmental stresses. A study aimed to investigate the effects of PBZ on morphological and biochemical traits of euonymus (Euonymus japonicas) exposed to NaCl stress. Plants were treated with three levels of PBZ (0, 500 and 1000 mg L-1) and four levels of NaCl (0, 50, 100, 150 mM). Morphological characteristics, electrolyte leakage (EL), chlorophyll content and antioxidant enzyme activity were changed by treatment with PBZ and NaCl stress. As compared to control plants, at 1000 and 500 mg L-1 PBZ, a decrease in height of 22.8% and 10.44% was observed, respectively. The highest number of lateral shoots was recorded in 1000 mg L-1 PBZ (non-salt-treated). The interaction of salinity and PBZ on shoot fresh weight was significant. At 150 mM NaCl + 1000 mg L-1 PBZ, shoot fresh weight increased by 30% compared to 150 mM NaCl. PBZ treated plants had highersuperoxide dismutase (SOD) activity than non- PBZ-treated plants. 1000 mg L-1 paclobutrazol was the best treatment for increasing the activity of this enzyme. PBZ mitigated the salinity stress and reduced EL of euonymus. Compared with 150 mM NaCl alone, the EL decreased by 24.4% in 1000 mg L-1 PBZ + 150 mM NaCl. According to the results of this study, it can be concluded that PBZ can be effective in tolerating euonymus to 150 mM NaCl.