Influence of external factors on secondary embryogenesis and germination in somatic embryos from leaves of Quercus suber

Abstract

Somatic embryogenesis was obtained in cultures of leaves from young seedlings of Quercus suber L. A twostage process, in which benzyladenine and naphthaleneacetic acid were added first at high and then at low concentrations, was required to initiate the process. Somatic embryos arose when the explants were subsequently placed on medium lacking plant growth regulators. The embryogenic lines remained productive, by means of secondary embryogenesis, on medium without growth regulators. However, this repetitive induction was influenced by the macronutrient composition of the culture medium. Both low total nitrogen content and high reduced nitrogen concentration decreased the percentage of somatic embryos that showed secondary embryogenesis. Our results suggest that alternate culture on medium that increases embryo proliferation and a low salt medium prohibiting embryo formation will partially synchronize embryo development. Chilling slightly reduced secondary embryogenesis but gave a modest increase in germination. Maturation under light followed by storage at 4 °C for at least 30 days gave the best results in switching embryos from an embryogenic pathway to a germinative one. Under these conditions 15% of embryos showed coordinated root and shoot growth and 35% formed either shoots or mostly roots. These percentages were higher than those of embryos matured in darkness. This result indicates that a specific treatment is required after maturation and before chilling to activate the switch from secondary embryo formation to germination.

Oak somatic and gametic embryos maturation is affected by charcoal and specific aminoacids mixture

“…Nevertheless, embryo dormancy and immaturity problems needed to be overcome. Osmoticum (high sucrose concentration) and chilling treatments had been tested in order to promote germination of cork oak somatic embryos (Fernández-Guijarro et al, 1995;García-Martín et al, 2001) and cytokinin application increased apex elongation of germinating cork oak somatic embryos (González-Benito et al, 2002;Hernández et al, 2003b).…”

Histology of Organogenic and Embryogenic Responses in Cotyledons of Somatic Embryos of Quercus suber L.

“…Somatic embryos of cork oak (Quercus suber L.) produce secondary embryogenesis on medium that lacks plant growth regulators (PGRs) (El Maâ taoui et al 1990;Ferná ndez-Guijarro et al 1995). This phenomenon, known as autoembryony, has been described for several species and is the basis of embryo cloning, giving this technique the potential to produce high multiplication rates (Merkle 1995).…”

Somatic Embryogenesis and Cryopreservation in Forest Species: The Cork Oak Case Study

“…Efforts were made since then to manipulate physical conditions in order to promote the adequate accumulation of reserves (Fernandes, 2011;. Fernández-Guijarro et al (1995) reported that somatic embryos from cork oak young seedlings increased maturation under light followed by storage at 4 °C, and that controlled starvation could benefit synchronization.…”