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 pre-treatment of seeds with gibberellic acid (۱۲۵, ۲۵۰, and ۵۰۰mg/kg) and salicylic acid (۱۰۰, ۲۰۰, and ۳۰۰mg/l), and the second factor was five concentrations (۰, ۲۵, ۵۰, ۷۵, and ۱۰۰mg /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 non-primed seeds. A comparison of means showed that seed priming with gibberellic acid ۲۵۰mg/kg increased germination ۲۵% compared to an unprimed seed. Conclusions: The response of this species to seed pre-treatment with gibberellic acid has the most effect. The seed pre-treatment technique with the mentioned treatment could increase germination and establish seedling by improving germination percentage and speed under allelopathic stress before planting.