Large-scale propagation of oil palm (Elaeis guineensis, Jacq.) is difficult due to its single apical meristem. Thus, obtaining plants is mainly through seed germination, and a long growing period is required before oil production is possible. An alternative to large-scale seedling production is indirect somatic embryogenesis. The aim of this study was to analyze the somatic embryogenesis process in oil palm (E. guineensis Jacq.) with amino acids and low concentrations of auxins. The Tenera hybrid was analyzed by cytochemical and ultrastructural methods and was used to regenerate oil palm plants. First, calli were induced in MS culture media supplemented with 2,4-D and picloram. Two types of calli were obtained, characterized by beige or translucent color. Beige calli had embryogenic characteristics, such as large nuclei with prominent nucleoli, and they were multiplied for 8 months in MM culture (half strength MS, 1 mg L 2,4-D, 2 mg L 2iP, 1 mg L IBA, 250 mg L citric acid, 10 mg L cysteine, 100 mg L inositol, 1 mg L thiamine, 1 mg L pyridoxine, 1 mg L nicotinic acid, 1 mg L glycine, 200 mg L malt extract, and 100 mg L casein hydrolysate). After multiplication, the MCB culture medium (half strength MS, supplemented with 0.25 mg L NAA, 2 mg L BAP, MM vitamins and 200 mg L malt extract, and 100 mg L casein hydrolysate) was the most efficient for embryo formation, showing meristematic centers with totipotent cells in histochemical analyses. The somatic embryos were developed and germinated in MG medium (half strength MS, 0.45 mg L IAA, 0.25 mg L BAP, and MM vitamins), transplanted into polyethylene tubes containing pine bark substrates, and acclimatized in a greenhouse, achieving a 97% survival rate. The use of picloram for callus induction and somatic embryogenesis is advantageous and multiplication in MM medium is an important step for increasing cell mass. The calli with light beige color and nodular structures have meristematic cells with dense cytoplasm and totipotential features that later give rise to protoderm, procambium, and ground meristem during the globular, cordiform, and torpedo embryogenesis phases. In MCB medium, the concentration of vitamins and amino acids are crucial for somatic embryogenesis.

The plant micro-propagation in bioreactor systems is regarded as one way to reduce cost by automation and production scheduling. This research was carried out in order to obtain an efficient procedure for clone production of Eucalyptus camaldulensis on different types of bioreactor including continuous and temporary immersion bioreactor. To do so, the apical meristems (1 mm) and the apical meristems with adjacent tissue (2,5 mm) were used as initial explants. These tissues were cultured, for 60 days, in semisolid culture medium supplemented with 1 mg L -1 indole acetic acid (IAA) and 0.32 mg L -1 benzylaminopurine (BA). After 60 days, the meristems with adjacent tissue were transferred to a continuous immersion bioreactor and maintained in dark or light conditions. In order to verify the effect of the explant source on bioreactor multiplication, the explants subcultured from meristems multiplied in semisolid culture medium and the meristems multiplied in continuous immersion bioreactor were tested and maintained in dark conditions. After establishing this parameters, the multiplication experiments were carried out in continuous and temporary immersion and the multiplied explants were then rooted in MS medium supplemented with 0, 2, 4, 8 and 20 mg L -1 indole butyric acid (IBA) and kept in the dark or under controlled lighting conditions. After that, the rooting the plants were acclimatized in mist chamber. The meristem with adjacent tissue favored a greater number of buds/explants. The continuous immersion bioreactor in the dark provided higher shoots number and multiplication rate. The rooting was better on culture medium without auxin and kept in the dark for 15 days or the culture medium supplemented with auxin and maintained under light with 100% plantlet rooting. The Eucalyptus camaldulensis acclimatization was efficient, with high survival rate (76%). It was possible to establish the procedure for bioreactor micro-propagation of Eucalyptus camaldulensis large-scale clones.

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This study aimed to assess the influence of culture medium and cytokinin type on in vitro multiplication of an Eucalyptus grandis x E. urophylla hybrid clone via temporary immersion bioreactor (TIB ®). JADS, modified MS at a (NO 3ˉ) :(NH 4 +) ratio, and WPM were used as liquid media; and BAP, KIN, and TDZ were the cytokinins used in the study. According to the results, explants under the influence of modified MS presented better results for all traits. BAP was the most suitable plant growth regulator for axillary bud shoot proliferation. By the leaf histological analysis, most of the shoots grown in the presence of BAP either exhibited normal morphology or only a few hyperhydricity symptoms. All these results were obtained at 19 days after in vitro cultivation, a shorter period when compared with other works in the literature, showing the protocol efficiency in the multiplication of this hybrid clone using TIB ® .

The objective of this work was to elucidate the growth curve of Eucalyptus camaldulensis Dehn. calli analyzing their anatomical modifications. A sigmoid aspect of the growth curve of the calli fresh matter was observed, with five different phases (lag, exponential, linear, deceleration and decline). In the lag phase, the highest growth percentage 87%, was observed, which reduced during the evaluation period to 17% in the linear phase. As for the anatomical analyses, cellular multiplications was observed during the lag and exponential phases and increase in cell size during the linear phase, promoting the calli volume growth and the establishment of the globular conformation