Evaluation of In Vitro Shoot Elongation and Rooting of Date Palm, and Determination of Physiological Characteristics of Regenerated Plantlets

The effects of various culture conditions on shoot elongation, rooting and plantlet acclimatization were tested. Adventitious shoots obtained through direct organogenesis of date palm (Phoenix dactylifera L.) cv. ‘Mejhoul’ were used as explants. The effects of culture medium texture, plant growth regulators, polyvinylpyrrolidone, adenine, myo-inositol, L-glutamine, and carbon source on in vitro plantlet quality and subsequent acclimatization were evaluated. The most effective culture medium was the semi-solid and half-strength Murashige and Skoog medium without plant growth regulators, supplemented with 30 g L-1 sucrose. After 3 months of culture on this medium, the average shoot length was 13.6 cm, the average number of adventitious roots per shoot was 3.6, and the average root length was 3.85 cm. The survival rate of these plantlets in acclimatization was 90%. On the other hand, liquid medium, plant growth regulators, polyvinylpyrrolidone, adenine, myo-inositol and L-glutamine did not increase the survival rate during acclimatization. Along with these experiments, some physiological characteristics of the plantlets obtained in vitro were also determined. Chlorophyll content and fluorescence, foliar surface and stomatal conductance were measured after 3 months of culture in each medium. The ranges were as follows: Chlorophyll content, 11.7-31.8 CCI; chlorophyll fluorescence, 0.633-0.795; foliar surface, 7.35-13.29 cm2; and stomatal conductance, 10.3-36.0 mmol m-2 s-1. Interestingly, positive correlations between the physiological characteristics of the plantlets and their survival percentage in the glasshouse were revealed. The findings of this investigation will be valuable for large-scale and cost-saving production of date palm cv. ‘Mejhoul’ plants.