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Abstract
This work was carried out in the Biotechnology Dept. Central Laboratory for Date Palm Research and Development, ARC. Giza, and Botany Dept. plant physiology branch, Faculty of Agriculture, Cairo University through 2013-2016. This study aimed to study effect of NAA with different types of cytokinins (BA, Kin, and 2iP) added alone or combined at 1 mg l⁻¹ and another experiment the effect of 2,4-D at 0.1, 0.5 and 1 mg l⁻¹ on growth character and morphogenesis of date palm (Siwy) via direct organogenesis. The obtained results indicated that highest percentage of responsive explants (36.36%) was observed on a medium containing 1 mg l⁻¹ NAA combined with 1 mg l⁻¹ each of BA, Kin, and 2iP whereas 9.20 shoots per explant formed after 32 weeks of culture and 22.22% was observed on a medium containing 1 mg l⁻¹ 2,4-D where 7.3 shoots per explant. In contrast, the medium containing 1 mg l⁻¹ NAA combined with 1 mg l⁻¹ of only one cytokinin enhanced root formation but completely inhibited shoot development. Typically, overt organogenesis is preceded by the appearance of meristemoids. These meristemoids are considered as a key of the morphological feature of de novo organogenesis. Therefore, biochemical and histological analyses were studied to increase our knowledge about date palm direct organogenesis. Biochemical analysis showed that, the ratio of auxin/cytokinin affected by factors such as total indoles and total phenols concentrations as well as peroxidase and polyphenoloxidase activities affected on the budding directly from shoot tips. Histological observation showed that shoots were originated from the ground tissue, mainly from tissue surrounding the vascular tissue in the explant. Then the vascular cylinder of the newly shoots connected with the neighboring vascular bundle of the explant by developing some tracheal elements, and thereafter shoots were elongated in the following sixteen weeks