Effects of temperature, light conditions and gibberellic acid on the in vitro germination of Protea cynaroides L. embryos
Poor and inconsistent germination of Protea cynaroides seeds are often observed in soil. A protocol based on embryo culture was developed for efficient in vitro propagation of P. cynaroides. The effects of temperature, light conditions and gibberellic acid (GA3) on the in vitro germination of P. cynaroides embryos were studied. The results showed that the use of alternating temperatures of 21/12°C (light/dark) significantly improved the germination percentage of the embryos, where 90% of embryos germinated, compared to a maximum of 55% when grown under a constant temperature of 25°C. Mean cotyledon fresh mass of embryos that germinated on media containing gibberellic acid (2.89, 28.89 μM GA3) were significantly higher than those cultured on media without growth regulators. Conversely, root growth was severely inhibited in embryos germinated on media containing gibberellic acid. The in vitro-germinated seedlings were successfully transplanted to a peat/coir/sand mixture in the mist bed.
Key words: Alternating temperature, embryo culture, gibberellic acid, King Protea, Proteaceae.