Optimizing rooting and survival of oil palm (Elaeis guineensis) plantlets derived from somatic embryos

Abstract

In species of the Arecaceae, initial conversion of somatic embryos to non-rooted plantlets (those with only shoot development and no roots) is common. A consistent methodology for improving rooting and survival of oil palm plantlets derived from somatic embryos was developed. Two experiments were carried out. In the first, non-rooted shoots regenerated via somatic embryogenesis were inoculated in nutrient medium supplemented with 0, 53.7, or 107.4 μM indole-3-butyric acid (IBA) or 1-naphthaleneacetic acid (NAA). In the second, the optimum treatment as determined in the first experiment was evaluated in three culture systems: semi-solid medium (SS), stationary liquid (SL), and doublephase system (DP), with and without the addition of activated charcoal. Next, the plantlets were acclimatized in a greenhouse, where the influence of the presence or absence of roots, the number of roots, the length of the main root, and the height of the shoot on survival were assessed. Supplementation with 53.7 μM IBA and the DP system without activated charcoal provided the highest percentage of rooted plantlets (92.9%) and number of roots (6.3) and improved the length of the aerial parts (11.0 cm) and the survival of the plantlets during the acclimatization (82.1%). The best survival of plantlets was obtained when they were acclimatized with at least one root and with a height greater than 7.5 cm.

Height and number of shoots on the survival and development of micropropagated bamboo plantlets during pre-acclimatization

“…For many species, this stage is determinant for the success of the commercial production of micropropagated plantlets, since, in the laboratory, they are under an environment with high relative humidity, reduced light intensity, limited gas exchange and constant temperature and photoperiod, conditions very different from when transplanted to the natural environment. Accordingly, plants developed in vitro become heterotrophic and may exhibit limited structural and functional characteristics and, when subjected to acclimatization, are exposed to moderate or severe environmental stress (Van Huylenbroeck & Debergh 1996, Luis et al 2010, Mishra et al 2011, Singh et al 2013, Gomes et al 2015. Moreover, for bamboo, there is also the heterogeneous size of the plants and the number of clusters aggregated to the plantlets when they are taken to acclimatization, which may interfere in the transpiration, energy metabolism, vigor and emission of new shoots during the ex vitro stage, characteristics that may quickly lead to the plant death under greenhouse conditions.…”

“…Thus, the knowledge of the gain in biomass, due to the organogenic process, both for shoots and roots, may be decisive in predicting the survival rate of large-scale plants, since structures with a higher biomass can enable plants to more easily overcome the environmental differences and other types of stress resulting from acclimatization. The unequal formation of shoots and roots is recurrent in plants grown in vitro, and may be attributed to the species or factors such as explant origin, cultivation system (liquid medium, semi-solid medium, bioreactors) and unequal physiological activity of meristematic cells, or be caused by somaclonal variation (Darwesh 2015, García-Ramírez et al 2015, Gomes et al 2015.…”

Assessing the influence of subcultures and liquid medium during somatic embryogenesis and plant regeneration in oil palm (Elaeis guineensisJacq.)

“…After their regeneration the plants originating from the somatic embryos of aggregates submitted to a liquid medium were separated and then transferred to test tubes (25 × 150 mm) containing doublephase MS medium (5 mL of liquid medium over 10 mL of semi-solid medium), complemented with 57 µM indole-3-butyric acid (IBA) and 30 g L −1 sucrose in order to improve root formation, following the methodology proposed by Gomes, Bartos, and Scherwinski-Pereira (2015).…”

“…Somatic embryos germinated in plants with a vigorous development of the aerial part, although most of them were lacking roots ( Figure 2(e and f)). And as described by Gomes et al (2015), a complementary stage was also required in this study in order to optimise root formation in regenerated plants for submission to acclimatisation (Figure 2(g and h)). Once they were rooted, acclimatised plants showed a 95.2% survival rate at the end of 90 days (Figure 2(i-k)).…”

In vitro conservation of blackberry genotypes under minimal growth conditions and subsequent large-scale micropropagation

“…Acclimatization was accomplished by removing the explant shoots from their culture media, and planting them in 200 mL plastic cups containing Bioplant commercial substrate, after washing the roots with running water to remove culture medium residues (Gomes et al, 2015). The explants were cultivated for 30 days in a greenhouse covered with transparent polyethylene film (150 µ), with 75±5%, relative humidity, at 27±4°C, and 450-500 μmol m -2 s , with the nozzles at a distance of about 1.5 m. After cultivation, the survival rate of plantlets was evaluated.…”