Determination of the date palm cell suspension growth curve, optimum plating efficiency, and influence of liquid medium on somatic embryogenesis.

Understanding the behavior of date palm (Phoenix dactylifera L.) cell suspension growth and differentiation would foster effective utilization for mass micropropagation and various in vitro investigations. The objectives of this study were to define the growth curve, identify the optimum plating density, and examine the efficiency of somatic embryogenesis of date palm suspension culture on solid and liquid media. Cell suspensions were established from shoot tip-induced callus of cv. Barhee inoculated in MS medium containing 10 mg l-1 naphthaleneacetic acid and 1.5 mg l-1 2-isopentenyladenine. Various growth phases including lag, exponential, linear, progressive deceleration, and stationary, along with their specific onsets and durations, were identified based on packed cell volume method. The growth pattern characterizing the exponential phase in date palm cell suspensions commenced 4 weeks after culture initiation which makes this period the most suitable for subculturing, assessment of the effects tissue culture factors, and in vitro selection. The effect of cell plating density on cell growth after transferring to solidified medium was also determined. The highest plating efficiency, 14.6%, was obtained at cell density of 10,000 cells ml-1. To stimulate somatic embryogenesis, cell suspension masses were transferred to agar or liquid media devoid of phytohormones. Plant regeneration was marked by the development of globular somatic embryos which progressively matured and germinated. Culturing suspension mass in liquid medium expedited regeneration and resulted in 3.5-fold more somatic embryos than agar medium. [ABSTRACT FROM AUTHOR]