An investigation into the potential of developing an in vitro method for propagating strelitziaceae

Abstract

A study was conducted to investigate the effects of: i) various media compositions and wounding treatments on the in vitro germination, growth and regeneration of Strelitzia reginae plantlets derived from zygotic embryos, ii) antioxidants, plant growth regulator (PGR) concentrations and plant tissue wounding treatments on phenolic compound production. One experiment consisted of 8 medium types including different combinations of Murashige and Skoog (MS) medium strength, activated charcoal and vitamin supplements. Twelve replicates were used for each treatment. In another experiment, germinated plantlets were subjected to 2 wounding treatments; (unwounded explants (control) and explants longitudinally sectioned through the apical meristem). The explants were transferred to ten different regeneration media consiting of different concentrations and combinations of auxin and cytokinin supplements and antioxidants. Ten replicates were used for each treatment. Results indicated the positive role of activated charcoal (AC) in reducing oxidative browning of embryo explants. The highest germination rate of embryos was observed in media containing AC without vitamin supplementation. Germination significantly decreased with the addition of vitamins. With regard to effects of various media compositions and wounding treatments on in vitro growth and regeneration of Strelitzia, significant results were achieved with 1-naphthalene acetic acid (NAA) and 6-benzylaminopurine (BAP) concentrations on explant discoloration and callus formation. The antioxidant treatments, activated charcoal (AC) and ascorbic acid (AA) significantly affected explant discoloration, the induction of callus and the length of roots developed. Wounding treatments affected plant height, increased explant height and callus formation. Interactions between higher NAA and BAP concentrations together with wounding resulted in the most effective treatment in reducing explant discoloration at the media contact point. Furthermore, results showed the various NAA and BAP concentrations to significantly affect phenolic exudation. The media containing the highest PGR concentration resulted in the highest phenol content. AC significantly reduced the total phenol content of media by 53%, compared with AA. Phenolic exudation was significantly increased as a result of explant wounding. Various interactions between the NAA and BAP concentrations, antioxidants and wounding affected phenolic exudation and the total phenol content of media. This study provides insight into the contributing factors and methods of overcoming the major problem of phenolic oxidation and promoting the in vitro growth and regeneration of Strelitzia.