We developed an efficient and simple system for inducing somatic embryogenesis and regenerating plantlets from mature zygotic embryos of oil palm. Embryogenic calli were induced from mature zygotic embryos of oil palm on modified Murashige and Skoog medium with 2,4-dichlorophenoxyacetic acid or picloram, alone or in combination with activated charcoal. The greatest frequency of embryogenic callus induction (97.5%) was obtained by culturing mature zygotic embryos on callus induction medium with 450 μM picloram and 2.5 gL −1 activated charcoal. Embryogenic calli proliferated on a medium with a reduced concentration of picloram. Embryogenic calli were then subcultured on a medium supplemented with 12.3 μM 2-isopentenyladenine and 0.54 μM naphthaleneacetic acid, with subcultures at 4-wk intervals. Somatic embryos were regenerated on a medium with Murashige and Skoog macro-and micronutrients at halfstrength concentrations supplemented with 20 gL −1 sucrose, 2.5 gL −1 activated charcoal, and 2.5 gL −1 Phytagel. Detailed histological analysis revealed that somatic embryogenesis followed an indirect pathway. Primary calli were observed after 4-6 wk of culture and progressed to embryogenic calli at 12 wk. Embryogenic cells exhibited dense protoplasm, a high nucleoplasmic ratio, and small starch grains. Proembryos, which seemed to have a multicellular origin, formed after 16-20 wk of culture and successive cell divisions. Differentiated somatic embryos had a haustorium, a plumule, and the first and second foliar sheaths. In differentiated embryos, the radicular protrusion was not apparent because it generally does not appear until after the first true leaves emerge.

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The morphogenic potential of nodal explants of Piper aduncum and Piper hispidinervum (Piperaceae) was investigated and a protocol for rapid micropropagation is described. An experiment based on the saline formulation of Murashige and Skoog (MS) and Wood Plant medium (WPM) combined with different N6-benzylaminopurine (BAP) and 1-naphthalene acetic acid (NAA) concentrations was evaluated. After determining the optimal concentration of growth regulators, the multiplication rates for the species, which were distributed in five subcultures, was assessed, and the number of plantlets produced in this period was recorded. After assessing the plants from all five subcultures, plantlets with well-developed root and shoot systems were transferred to pots containing substrate for acclimatization. The culture of nodal segments of P. aduncum and P. hispidinervum on hormone-free medium was shown to be a suitable method for micropropagation due to the high multiplication rate and good plant development. The use of BAP or BAP + NAA resulted to formation of vitrified multiple shoots and callus formation at the base of the microcuttings. Even at concentrations lower than 1 mg L-1 , the use of BAP resulted in vitrified multiple shoot and callus formation, without significantly improving the multiplication rates. For both species, the first subculture resulted in the greatest number of axillary buds, and mainly for P. hispidinervum, the MS medium was the most appropriate for in vitro multiplication of microcuttings. The species showed 100% root formation, and acclimatization of plants from the fifth subculture in a greenhouse resulted in 100% survival.