Effect of Seed Priming with GA and SA on the Improvement of Germination Characteristics of Hibiscus sabdariffa Seeds Under Allelopathic Stress of Eucalyptus camaldulensis

Aims: Germination is one of the important stages of plant lifecycles that may be affected by different natural stress such as allelopathic. This study was performed to investigate the effects of priming with gibberellic and salicylic acid on germination improvement and resistance of Hibiscus sabdariffa under stress with allelopathic compounds of Eucalyptus camaldulensis. Materials Methods: The experiment was conducted as a factorial experiment in a completely randomized design with four replications in laboratory conditions. The first factor consists of pretreatment of seeds with gibberellic acid (125, 250, and 500mg/kg) and salicylic acid (100, 200, and 300mg/l), and the second factor was five concentrations (0, 25, 50, 75, and 100mg /l) of allelopathic compounds of eucalyptus. Studied characteristics have consisted of germination percent, germination speed, root length, shoot length, seedling length, and vigor index. Findings: Results showed that Eucalyptus allelopathic extract has an inhibitory effect on seed germination of H. sabdariffa. When the extract concentration increased, the germination and seedling growth decreased significantly. In contrast, seed priming with gibberellic and salicylic acid increased the measured characteristics at all levels compared to nonprimed seeds. A comparison of means showed that seed priming with gibberellic acid 250mg/kg increased germination 25% compared to an unprimed seed. Conclusions: The response of this species to seed pretreatment with gibberellic acid has the most effect. The seed pretreatment technique with the mentioned treatment could increase germination and establish seedling by improving germination percentage and speed under allelopathic stress before planting.