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  • Author or Editor: Carlos Alberto Lecona-Guzmán x
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The effect of NaCI salinity on growth and development of somatic embryos of Habanero pepper was examined. Addition of 75 and 100 mm NaCI into the medium greatly increased the growth and development of somatic embryos and both of these concentrations favored the proliferation of somatic embryos. However, supplementation of 200 and 300 mm NaCI to the medium showed a negative effect on the growth and development of somatic embryos. Concentration increases of NaCl provoked a significant reduction of the embryos survival rate with the average lethal dose (46%) being registered in the treatment of 100 mm. Furthermore, a lower tolerance to salt stress (NaCl) was observed in deformed somatic embryos. Concentrations of 200 and 300 mm NaCl significantly delayed development in the surviving embryos in both treatments. These embryos remained at the globular stage throughout culture time. At 75 mm NaCl, most of the embryos were observed in the torpedo stage. However, the embryos exposed to 100 mm NaCl were observed mainly in globular and cotiledonar stages. It is quite likely that the transition from one intermediate stage of development to another occurs rapidly. With the exception of the concentration at 300 mm NaCl, salt stress stimulated embryonic germination, particularly at 100 mm NaCl. The content of proline in somatic embryos increased substantially in response to salinization. The results suggest that somatic embryos of C. chinense can tolerate concentrations of NaCl up to 100 mm without their development being affected. Moreover, they have sufficient cellular mechanisms to tolerate salinity at relatively higher levels.

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Factors such as slow growth, low rates of sexual and asexual reproduction, and viability of seeds among others limit the massive propagation of Agave americana L. by conventional methods. In this study, callus induction and shoot proliferation was determined in A. americana using Murashige and Skoog (MS) medium supplemented with dicholorophenoxyacetic acid (2,4-D) and 6-benzyl adenine (BA). Meristematic tissue was used as the explants, and were placed on MS medium supplemented with 30.0 g·L−1 sucrose with 0.11, 0.18, or 0.45 μm 2,4-D and 11.0, 22.0, 38.2, 44.0, 58.7, or 73.3 μm BA. Treatments were implemented according to factorial experimental design 3 × 6. After 1 month, the number of explants with callus was determined, whereas the numbers of shoots per explant were monitored after 4, 16, 20, and 36 weeks. The maximum percent of explants with callus was obtained with 0.11 μm 2,4-D and 58.7 and 73.3 μm BA, whereas the maximum numbers of shoots per explant (71) were obtained with 0.11 μm 2,4-D and 73.3 μm BA. The effect of different concentrations of indolebutyric acid (IBA) in the rooting of shoots was evaluated. There were no significant effects of IBA on the number of roots, root length, and axillary roots. Plantlets were acclimatized in the glasshouse and they did not show any phenotypic alteration. This is a highly efficient protocol for the in vitro propagation of A. americana via indirect organogenesis.

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