Effect of gibberellic and salicylic acid on germination improvement and seedling resistance of Cassia angustifolia vahl. under allelopathic stress of eucalyptus camaldulensis compounds

The aim of this study was to investigate the effects of gibberellic and salicylic acid on germination improvement and protection of Cassia angustifolia under allelopathic stress of Eucalyptus camaldulensis compounds in laboratory conditions. Treatments consisted of pretreatment with gibberellic acid (125, 250, and 500 ppm) and salicylic acid (100, 200, and 300 mg / l), and 5 concentrations of extracted allelopathic compounds of eucalyptus aerial and terrestrial organs (0, 25, 50, 75, and 100 mg / l). Each treatment had four replications and a factorial experiment in completely randomized design was performed. Results of analysis of variance indicated that the interaction effect of pretreatment and allelopathy on all measured traits was significant (p≤0.01). Means comparison showed that eucalyptus extract has allelopathic inhibitory effects on seed germination and early growth of Cassia angustifolia seedlings such that seed pre-treatment with chemical stimulants improved germination percentage and speed and also early growth of seedlings. Seed pre-treatment with gibberellic acid 500 ppm had the best effect on improvement of germination and early growth of seedlings. Overall, the results showed that Cassia angustifolia's response to seed pre-treatment with gibberellic acid was positive, and the seed pretreatment technique with gibberellic acid 500 ppm before planting decreased significantly the inhibitory effects of eucalyptus allopathic compounds at germination stage.