<?xml version="1.0" encoding="UTF-8"?><xml><records><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Barra-Jimenez, Azahara</style></author><author><style face="normal" font="default" size="100%">Blasco, Miquel</style></author><author><style face="normal" font="default" size="100%">Ruiz-Galea, Mar</style></author><author><style face="normal" font="default" size="100%">Celestino, Cristina</style></author><author><style face="normal" font="default" size="100%">Alegre, Jesús</style></author><author><style face="normal" font="default" size="100%">Arrillaga, Isabel</style></author><author><style face="normal" font="default" size="100%">Toribio, Mariano</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Cloning mature holm oak trees by somatic embryogenesis</style></title><secondary-title><style face="normal" font="default" size="100%">TREES-STRUCTURE AND FUNCTION</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">adult trees</style></keyword><keyword><style  face="normal" font="default" size="100%">Arabinogalactan protein</style></keyword><keyword><style  face="normal" font="default" size="100%">Integuments</style></keyword><keyword><style  face="normal" font="default" size="100%">Ovules</style></keyword><keyword><style  face="normal" font="default" size="100%">Quercus ilex</style></keyword><keyword><style  face="normal" font="default" size="100%">vegetative propagation</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2014</style></year></dates><publisher><style face="normal" font="default" size="100%">SPRINGER</style></publisher><pub-location><style face="normal" font="default" size="100%">233 SPRING ST, NEW YORK, NY 10013 USA</style></pub-location><volume><style face="normal" font="default" size="100%">28</style></volume><pages><style face="normal" font="default" size="100%">657-667</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Integuments from holm oak developing ovules were suitable initial explants to obtain embryogenic lines from which plants could be regenerated. The implementation of multivarietal forestry as part of breeding strategies is expected to provide more productive forest plantations. To achieve this, a reliable and effective method for mass production of clonal plants is needed. Somatic embryogenesis is considered the enabling technology for implementing multivarietal forestry. The holm oak (Quercus ilex L.) is a Mediterranean evergreen tree of economic interests because of the acorn production for animal feed and edible fungi mycorrhization. The aim of this work was to obtain clonal plants by inducing somatic embryogenesis in tissues of female flowers from mature trees. The influence of the developmental stage of the explant, the genotype and medium composition, and the effect of arabinogalactan proteins on the induction frequency, were assessed. Somatic embryogenesis induction (frequency ranging from 1.2 to 3.2 %) was restricted to ovules excised at an advanced stage of development, when they were at least 3-4 mm wide and the rest of the ovules within the ovary had aborted. Somatic embryos arose from the integuments of those fertilized ovules. Embryogenic response was obtained on media with and without plant growth regulators. All the genotypes that were cultured on medium containing ``as reported by Schenk and Hildebrandt (Can J Bot 50:199-204, 1972){''} SH macronutrients could be captured. Treatments including Larix arabinogalactan proteins did not improve induction, while those from Acacia inhibited the embryogenic response. Several embryogenic lines were multiplied by repetitive embryogenesis on medium lacking plant growth regulators. Mature somatic embryos of three genotypes were germinated at frequencies ranging from 41 to 58 %, and converted into plants at frequencies from 11 to 30 %, depending on the genotype.</style></abstract></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Jiménez, Jesús</style></author><author><style face="normal" font="default" size="100%">López-Vela, Dolores</style></author><author><style face="normal" font="default" size="100%">Ruiz-Galea, Mar</style></author><author><style face="normal" font="default" size="100%">Celestino, Cristina</style></author><author><style face="normal" font="default" size="100%">Toribio, Mariano</style></author><author><style face="normal" font="default" size="100%">Alegre, Jesús</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Embryogenic suspensions of adult cork oak: the first step towards mass propagation</style></title><secondary-title><style face="normal" font="default" size="100%">Trees</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">á somatic</style></keyword><keyword><style  face="normal" font="default" size="100%">embryogenesis á suspension culture</style></keyword><keyword><style  face="normal" font="default" size="100%">micropropagation</style></keyword><keyword><style  face="normal" font="default" size="100%">micropropagation á quercus suber</style></keyword><keyword><style  face="normal" font="default" size="100%">Quercus suber</style></keyword><keyword><style  face="normal" font="default" size="100%">Somatic embryogenesis</style></keyword><keyword><style  face="normal" font="default" size="100%">Suspension culture</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2012</style></year><pub-dates><date><style  face="normal" font="default" size="100%">2012///</style></date></pub-dates></dates><urls><web-urls><url><style face="normal" font="default" size="100%">http://www.springerlink.com/index/10.1007/s00468-012-0763-yhttp://link.springer.com/10.1007/s00468-012-0763-y</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">27</style></volume><pages><style face="normal" font="default" size="100%">13 - 23</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Protocols have been established to clone adult cork oak trees by somatic embryogenesis using semisolid medium. However, for economically viable mass propagation, embryogenic cultures in liquid medium need to be developed. In this study, suspension cultures were initiated from embryo clusters obtained by secondary embryogenesis on a gelled medium lacking plant growth regulators. After 6 days of culture, these embryo clusters generated high cell density suspensions that also contained small organized structures (embryos and embryogenic clumps). As the culture duration increased, tissue necrosis and fewer embryogenic structures were observed and the establishment of suspension cultures failed. An alternative method was found adequate for initiation of embryogenic suspensions: embryo clusters from gelled medium were brieﬂy shaken in liquid medium and detached cells and embryogenic masses of 41–800 lm were used as inoculum. Maintenance of embryogenic suspensions was achieved using a low-density inoculum (43 mg l -1 ) by subculturing four embryogenic clumps of 0.8–1.2 mm per 70 ml of medium. Proliferation ability was maintained for almost 1 year through ten consecutive subcultures. The initiation and maintenance protocols ﬁrst developed for a single genotype were effective when tested on 11 cork oak genotypes.</style></abstract><issue><style face="normal" font="default" size="100%">1</style></issue></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Celestino, Cristina</style></author><author><style face="normal" font="default" size="100%">Fernández-Guijarro, B</style></author><author><style face="normal" font="default" size="100%">Hernández, Inmaculada</style></author><author><style face="normal" font="default" size="100%">López Vela, Dolores</style></author><author><style face="normal" font="default" size="100%">Carneros, Elena</style></author><author><style face="normal" font="default" size="100%">Jiménez García, Jesús</style></author><author><style face="normal" font="default" size="100%">Cardo, L</style></author><author><style face="normal" font="default" size="100%">Alegre, Jesús</style></author><author><style face="normal" font="default" size="100%">Toribio, Mariano</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Growth data from a field trial of Quercus suber plants regenerated from selected trees and from their half-sib progenies by somatic embryogenesis</style></title><secondary-title><style face="normal" font="default" size="100%">Acta Horticulturae</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">Cork oak</style></keyword><keyword><style  face="normal" font="default" size="100%">field establishment</style></keyword><keyword><style  face="normal" font="default" size="100%">forest improvement</style></keyword><keyword><style  face="normal" font="default" size="100%">rejuvenation</style></keyword><keyword><style  face="normal" font="default" size="100%">vegetative propagation</style></keyword><keyword><style  face="normal" font="default" size="100%">woody plant micropropagation</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2009</style></year></dates><volume><style face="normal" font="default" size="100%">812</style></volume><pages><style face="normal" font="default" size="100%">493-498</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">The development of reliable clonal propagation technologies is a requisite for performing Multi-Varietal Forestry (MVF). Somatic embryogenesis is considered the tissue culture based method more suitable for operational breeding of forest trees. Vegetative propagation is very difficult when tissues are taken from mature donors, making clonal propagation of selected trees almost impossible. We have been able to induce somatic embryogenesis in leaves taken from mature oak trees, including cork oak (Quercus suber). This important species of the Mediterranean ecosystem produces cork regularly, conferring to this species a significant economic value. In a previous paper we reported the establishment of a field trial to compare the growth of plants of somatic origin vs zygotic origin, and somatic plants from mature trees vs somatic plants from juvenile seedlings. For that purpose somatic seedlings were regenerated from five selected cork oak trees and from young plants of their half-sib progenies by somatic embryogenesis. They were planted in the field together with acorn-derived plants of the same families. After the first growth period, seedlings of zygotic origin doubled the height of somatic seedlings, showing somatic plants of adult and juvenile origin similar growth. Here we provide data on height and diameter increases after two additional growth periods. In the second one, growth parameters of zygotic seedlings were also significantly higher than those of somatic ones, but there were not significant differences in height increase between seedlings and somatic plants of mature origin. In the third growth period, height and diameter increases of somatic seedlings cloned from the selected trees did not differ from those of zygotic seedlings, which were still higher than data from plants obtained from somatic embryos from the sexual progeny. Therefore, somatic seedlings from mature origin seem not to be influenced by a possible ageing effect, and plants from somatic embryos tend to minimize the initial advantage of plants from acorns.</style></abstract></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Celestino, Cristina</style></author><author><style face="normal" font="default" size="100%">Fernandez-Guijarro, B.</style></author><author><style face="normal" font="default" size="100%">Hernández, Inmaculada</style></author><author><style face="normal" font="default" size="100%">López Vela, Dolores</style></author><author><style face="normal" font="default" size="100%">Carneros, Elena</style></author><author><style face="normal" font="default" size="100%">Jiménez García, Jesús</style></author><author><style face="normal" font="default" size="100%">Cardo, L.</style></author><author><style face="normal" font="default" size="100%">Alegre, Jesús</style></author><author><style face="normal" font="default" size="100%">Toribio, Mariano</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Growth data from a field trial of Quercus suber plants regenerated from selected trees and from their half-sib progenies by somatic embryogenesis</style></title><secondary-title><style face="normal" font="default" size="100%">Acta Horticulturae</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">Cork oak</style></keyword><keyword><style  face="normal" font="default" size="100%">field establishment</style></keyword><keyword><style  face="normal" font="default" size="100%">forest improvement</style></keyword><keyword><style  face="normal" font="default" size="100%">rejuvenation</style></keyword><keyword><style  face="normal" font="default" size="100%">vegetative propagation</style></keyword><keyword><style  face="normal" font="default" size="100%">woody plant micropropagation</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2009</style></year><pub-dates><date><style  face="normal" font="default" size="100%">2009///</style></date></pub-dates></dates><urls><web-urls><url><style face="normal" font="default" size="100%">http://www.actahort.org/books/812/812_71.htm</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">812</style></volume><pages><style face="normal" font="default" size="100%">493 - 498</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">The development of reliable clonal propagation technologies is a requisite for performing Multi-Varietal Forestry (MVF). Somatic embryogenesis is considered the tissue culture based method more suitable for operational breeding of forest trees. Vegetative propagation is very difficult when tissues are taken from mature donors, making clonal propagation of selected trees almost impossible. We have been able to induce somatic embryogenesis in leaves taken from mature oak trees, including cork oak (Quercus suber). This important species of the Mediterranean ecosystem produces cork regularly, conferring to this species a significant economic value. In a previous paper we reported the establishment of a field trial to compare the growth of plants of somatic origin vs zygotic origin, and somatic plants from mature trees vs somatic plants from juvenile seedlings. For that purpose somatic seedlings were regenerated from five selected cork oak trees and from young plants of their half-sib progenies by somatic embryogenesis. They were planted in the field together with acorn-derived plants of the same families. After the first growth period, seedlings of zygotic origin doubled the height of somatic seedlings, showing somatic plants of adult and juvenile origin similar growth. Here we provide data on height and diameter increases after two additional growth periods. In the second one, growth parameters of zygotic seedlings were also significantly higher than those of somatic ones, but there were not significant differences in height increase between seedlings and somatic plants of mature origin. In the third growth period, height and diameter increases of somatic seedlings cloned from the selected trees did not differ from those of zygotic seedlings, which were still higher than data from plants obtained from somatic embryos from the sexual progeny. Therefore, somatic seedlings from mature origin seem not to be influenced by a possible ageing effect, and plants from somatic embryos tend to minimize the initial advantage of plants from acorns.</style></abstract></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Dı́ez, Jesús</style></author><author><style face="normal" font="default" size="100%">Manjón, José Luis</style></author><author><style face="normal" font="default" size="100%">Kovács, Gabor M</style></author><author><style face="normal" font="default" size="100%">Celestino, Cristina</style></author><author><style face="normal" font="default" size="100%">Toribio, Mariano</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Mycorrhization of vitroplants raised from somatic embryos of cork oak (Quercus suber L.)</style></title><secondary-title><style face="normal" font="default" size="100%">Applied Soil Ecology</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">Cork oak</style></keyword><keyword><style  face="normal" font="default" size="100%">ectomycorrhizas</style></keyword><keyword><style  face="normal" font="default" size="100%">Mycorrhization</style></keyword><keyword><style  face="normal" font="default" size="100%">Somatic embryogenesis</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2000</style></year></dates><volume><style face="normal" font="default" size="100%">15</style></volume><pages><style face="normal" font="default" size="100%">119-123</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">The technique described herein allows in vitro ectomycorrhizal synthesis in Quercus suber vitroplants raised from somatic embryos with Pisolithus tinctorius and Scleroderma polyrhizum strains. Only strains of this species coming from fruit bodies collected in Quercus suber stands (strain QS241 and strain QS247) formed ectomycorrhizas, and hence these species seem to exhibit host adaptation. The in vitro mycorrhization facilitated the development of secondary roots and the ex vitro weaning of cork oak vitroplants.</style></abstract></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Dı́ez, Jesús</style></author><author><style face="normal" font="default" size="100%">Manjón, José Luis</style></author><author><style face="normal" font="default" size="100%">Kovács, Gabor M.</style></author><author><style face="normal" font="default" size="100%">Celestino, Cristina</style></author><author><style face="normal" font="default" size="100%">Toribio, Mariano</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Mycorrhization of vitroplants raised from somatic embryos of cork oak (Quercus suber L.)</style></title><secondary-title><style face="normal" font="default" size="100%">Applied Soil Ecology</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">Cork oak</style></keyword><keyword><style  face="normal" font="default" size="100%">ectomycorrhizas</style></keyword><keyword><style  face="normal" font="default" size="100%">Mycorrhization</style></keyword><keyword><style  face="normal" font="default" size="100%">Somatic embryogenesis</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2000</style></year><pub-dates><date><style  face="normal" font="default" size="100%">2000///</style></date></pub-dates></dates><urls><web-urls><url><style face="normal" font="default" size="100%">http://linkinghub.elsevier.com/retrieve/pii/S0929139300000871</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">15</style></volume><pages><style face="normal" font="default" size="100%">119 - 123</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">The technique described herein allows in vitro ectomycorrhizal synthesis in Quercus suber vitroplants raised from somatic embryos with Pisolithus tinctorius and Scleroderma polyrhizum strains. Only strains of this species coming from fruit bodies collected in Quercus suber stands (strain QS241 and strain QS247) formed ectomycorrhizas, and hence these species seem to exhibit host adaptation. The in vitro mycorrhization facilitated the development of secondary roots and the ex vitro weaning of cork oak vitroplants.</style></abstract><issue><style face="normal" font="default" size="100%">2</style></issue></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Celestino, Cristina</style></author><author><style face="normal" font="default" size="100%">Picazo, M L</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Influence of 50 Hz electromagnetic fields on recurrent embryogenesis and germination of cork oak somatic embryos</style></title><secondary-title><style face="normal" font="default" size="100%">Plant cell, tissue and …</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">bioelectromagnetism</style></keyword><keyword><style  face="normal" font="default" size="100%">elf magnetic fields</style></keyword><keyword><style  face="normal" font="default" size="100%">germination</style></keyword><keyword><style  face="normal" font="default" size="100%">Quercus Suber L</style></keyword><keyword><style  face="normal" font="default" size="100%">Somatic embryogenesis</style></keyword><keyword><style  face="normal" font="default" size="100%">tissue culture</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1998</style></year></dates><volume><style face="normal" font="default" size="100%">54</style></volume><pages><style face="normal" font="default" size="100%">65-69</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Plant tissue culture techniques are carried out under environmentally controlled conditions in phytotrons. However, electric components of phytotrons generate electromagnetic ﬁelds that may act as a environmental factor inﬂuencing plant growth and morphogenesis. Isolated somatic embryos of Quercus suber, picked from embryogenic lines, were chronically exposed to a 50 Hz and 15 µT electromagnetic ﬁeld generated in a Helmholtz-coil system for 8 weeks, in order to examine if the extremely low frequency (ELF) magnetic ﬁeld (MF) affected the morphogenic behaviour of embryogenic cultures during recurrent embryogenesis. Germination of somatic embryos from genotype G7.1 was carried out under the same electromagnetic ﬁeld, and also under conditions in which the local geomagnetic ﬁeld was suppressed. The ELF MF did not inﬂuence the growth of embryogenic clumps of the assayed genotypes, but reduced the number of detachable embryos produced by genotype G3.27. The ELF MF did not modify the percentages of germination or plant formation of somatic embryos. However, somatic embryos had better germination when cultured under the suppressed geomagnetic ﬁeld condition.</style></abstract></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Celestino, Cristina</style></author><author><style face="normal" font="default" size="100%">Picazo, M. L.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Influence of 50 Hz electromagnetic fields on recurrent embryogenesis and germination of cork oak somatic embryos</style></title><secondary-title><style face="normal" font="default" size="100%">Plant cell, tissue and …</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">bioelectromagnetism</style></keyword><keyword><style  face="normal" font="default" size="100%">elf magnetic fields</style></keyword><keyword><style  face="normal" font="default" size="100%">germination</style></keyword><keyword><style  face="normal" font="default" size="100%">Quercus Suber L</style></keyword><keyword><style  face="normal" font="default" size="100%">Somatic embryogenesis</style></keyword><keyword><style  face="normal" font="default" size="100%">tissue culture</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1998</style></year><pub-dates><date><style  face="normal" font="default" size="100%">1998///</style></date></pub-dates></dates><urls><web-urls><url><style face="normal" font="default" size="100%">http://www.springerlink.com/index/J63G08P8G37N7373.pdf</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">54</style></volume><pages><style face="normal" font="default" size="100%">65 - 69</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Plant tissue culture techniques are carried out under environmentally controlled conditions in phytotrons. However, electric components of phytotrons generate electromagnetic ﬁelds that may act as a environmental factor inﬂuencing plant growth and morphogenesis. Isolated somatic embryos of Quercus suber, picked from embryogenic lines, were chronically exposed to a 50 Hz and 15 µT electromagnetic ﬁeld generated in a Helmholtz-coil system for 8 weeks, in order to examine if the extremely low frequency (ELF) magnetic ﬁeld (MF) affected the morphogenic behaviour of embryogenic cultures during recurrent embryogenesis. Germination of somatic embryos from genotype G7.1 was carried out under the same electromagnetic ﬁeld, and also under conditions in which the local geomagnetic ﬁeld was suppressed. The ELF MF did not inﬂuence the growth of embryogenic clumps of the assayed genotypes, but reduced the number of detachable embryos produced by genotype G3.27. The ELF MF did not modify the percentages of germination or plant formation of somatic embryos. However, somatic embryos had better germination when cultured under the suppressed geomagnetic ﬁeld condition.</style></abstract></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Fernández-Guijarro, Bárbara</style></author><author><style face="normal" font="default" size="100%">Celestino, Cristina</style></author><author><style face="normal" font="default" size="100%">Toribio, Mariano</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Influence of external factors on secondary embryogenesis and germination in somatic embryos from leaves of Quercus suber</style></title><secondary-title><style face="normal" font="default" size="100%">Plant Cell, Tissue and Organ Culture</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">Cork oak</style></keyword><keyword><style  face="normal" font="default" size="100%">culture media</style></keyword><keyword><style  face="normal" font="default" size="100%">plant regeneration</style></keyword><keyword><style  face="normal" font="default" size="100%">recurrent embryogenesis</style></keyword><keyword><style  face="normal" font="default" size="100%">repetitive embryogenesis</style></keyword><keyword><style  face="normal" font="default" size="100%">Somatic embryogenesis</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1995</style></year></dates><volume><style face="normal" font="default" size="100%">41</style></volume><pages><style face="normal" font="default" size="100%">99-106</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Somatic embryogenesis was obtained in cultures of leaves from young seedlings of Quercus suber L. A two- stage 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.</style></abstract></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Fernández-Guijarro, Bárbara</style></author><author><style face="normal" font="default" size="100%">Celestino, Cristina</style></author><author><style face="normal" font="default" size="100%">Toribio, Mariano</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Influence of external factors on secondary embryogenesis and germination in somatic embryos from leaves of Quercus suber</style></title><secondary-title><style face="normal" font="default" size="100%">Plant Cell, Tissue and Organ Culture</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">Cork oak</style></keyword><keyword><style  face="normal" font="default" size="100%">culture media</style></keyword><keyword><style  face="normal" font="default" size="100%">plant regeneration</style></keyword><keyword><style  face="normal" font="default" size="100%">recurrent embryogenesis</style></keyword><keyword><style  face="normal" font="default" size="100%">repetitive embryogenesis</style></keyword><keyword><style  face="normal" font="default" size="100%">Somatic embryogenesis</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1995</style></year><pub-dates><date><style  face="normal" font="default" size="100%">1995///</style></date></pub-dates></dates><urls><web-urls><url><style face="normal" font="default" size="100%">http://www.springerlink.com/index/10.1007/BF00051578</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">41</style></volume><pages><style face="normal" font="default" size="100%">99 - 106</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Somatic embryogenesis was obtained in cultures of leaves from young seedlings of Quercus suber L. A two- stage 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.</style></abstract><issue><style face="normal" font="default" size="100%">2</style></issue></record></records></xml>