Maturation Culture Of Somatic Embryogenesis In Dendrobium Candidum Wall Ex Lindl

During maturation, somatic embryos substantially differed from their zygotic counterparts not only in their reserve accumulations, but also in the acquisition of desiccation and embryo dormancy. However, somatic embryos can be induced to accumulate reserve, acquire desiccation tolerance and dormancy by a number of treatments and combinations, such as the addition of the plant hormone, abscisic acid (ABA), carbon sources, osmotic stress and slow drying. Therefore, it would be beneficial for somatic embryogenesis to optimize the culture conditions aimed at inducing the maturation of somatic embryos. Moreover, the enhancement of somatic embryo maturation will lead to a better understanding of the control of the physiological and biochemical process involved in embryo maturation.The effect of sucrose, polyethylene glycol-4000 (PEG-4000) and abscisic acid (ABA) were tested on the regulation of somatic embryos of Dendrobium candidum Wall ex Lindl cultured in liquid medium. Regulation was assayed by evaluating the ability of somatic embryos to develop with a desirable morphological appearance. Best results were obtained on 1/2 Murashige-Skoog basal medium supplemented with 58mM sucrose and 0.76μM ABA, where percentage of the regulated somatic embryos was 84.5. After 5 weeks on this medium, somatic embryos exhibited vigorous and regulated morphological appearance.Further, the effect of sucrose, polyethylene glycol-4000 (PEG-4000) and abscisic acid (ABA) on the accumulation of soluble proteins and sugars was also studied in somatic embryos cultured in liquid medium. Somatic embryos that initiated to histo-differentiation were cultured over five weeks. After that, the total soluble protein and sugar contents were measured. Maximum content of proteins was obtained from the embryo cultured on the medium containing 219mM sugar and 0.56μM ABA. The accumulation of soluble proteins was enhanced when the sucrose concentration increase from 58mM to 219mM. However, increasing concentrations of PEG-4000 resulted in lower content of soluble proteins, only 2% PEG slightly enhanced the accumulation of the total soluble proteins.In conclusion, the medium supplemented with 219mM sugar and 0.56μM ABA was best for the accumulation of soluble proteins in somatic embryos of Dendrobium candidum Wall ex Lindl.