GA3 acts as a germination promoter in wild castor bean ( Ricinus communis L.)

In this study, we focused on overcoming germination inability in wild castor bean by treatment with different concentrations of gibberellic acid (GA3) and potassium nitrate (KNO3). The caruncle of mature seeds of wild castor bean, collected from natural habitats in Türkiye, were removed at the seed tip. Seeds with or without caruncle were immersed in GA3 and KNO3 at concentrations of 0, 250, 500 and 1000 ppm. Germination and seedling growth parameters were evaluated. Removing the caruncle from the seeds significantly improved germination (from 14.7 to 73.5%) and seedling growth characteristics. Application of KNO3 to the seeds without caruncle shortened mean germination time. GA3 promoted root elongation, but shoot growth was induced by KNO3. Hydration had a stimulative effect on seedling fresh weight and dry matter, while the highest vigour index was identified in seeds primed with GA3. The beneficial effects of KNO3 and GA3 were maximal when treated with 500 ppm and 1000 ppm, respectively, while higher germination and better seedling growth were obtained from hydration compared to KNO3. It is suggested that the presence of the caruncle restricts germination and 1000 ppm GA3 acts as a germination promotor in wild castor bean seeds.