For initiation of roots, date palm shoots measuring approximately 6-8 cm long separated
and transferred on MS media consisting of supplements described as in materials and methods. Among the auxins, NAA is the most frequently exploited exogenous hormone for roots’ development of in vitro date palm’s shoots. However genotypic specificity of a particular cultivar resulted in variations for optimum concentrations of NAA. Therefore media with different concentrations of NAA were evaluated for attaining the best quality roots to achieve maximum ex vitro establishment of date palm (cv. Dhakki) plantlets. The results (Table 3) showed that number of roots increased with the ascending concentrations of NAA. 1.5 mg/l NAA favored the profuse rooting (Fig. 5d) of date palm shoots followed by 1 mg/l NAA. However, these roots were very thin. These results are in agreement with those obtained by Bekheet & Saker (1998). They found efficient rooting effect of 1 mg/l NAA rather than IBA and IAA at the same concentrations. On the other hand, Tissert (1984) reported profuse rooting of date palm plantlets on medium supplemented with 0.1 mg/l NAA. Table 3 shows that rising levels of NAA negatively affected the root length of date palm plantlets. When the rooted plantlets transplanted to ex vitro conditions, the marked variation in survival efficiency (Table 3) was observed among the plantlets rooted on MS medium provided with various concentrations of NAA. Of all plantlets transplanted ex vitro, the plantlets harvested from medium consisting of 0.5 mg/l NAA found to have highest survival proportion (83 %). The roots of these plantlets were thicker than the others (Fig. 5c). The plantlets obtained on the media supplemented with 0.1 mg/l NAA had greater survival efficiency (58 %) than plantlets harvested from 1 mg/l NAA and 1.5 mg/l NAA containing media (Table 3). These results are also reported by Johnson & Burchett (1991). They found highest survival rate in plantlets supplemented with lower concentrations of IBA and IAA despite of the fact that these plantlets had comparatively less number of roots than those obtained at higher concentrations of auxins.Thus it can be depicted from the results of this study that selection of appropriate concentration of NAA should be made to get plantlets with adequate number and length ofroots to achieve maximum ex-vitro establishment.