Resumen de Anatomical characterization of the Quercus suber zygotic embryo development
Dolores López-Vela, Cristina Celestino Mur, Elena Carneros García, Mariano Toribio Iglesias, Jesús Alegre Álvaro
To improve plant regeneration by somatic embryogenesis in Quercus suber the knowledge of zygotic embryogenic process is of great interest. One of the needed tools is to have an external marker of embryo development to make easier field sampling of fruits with embryos at precise developmental stages. Recently, the different stages of development in zygotic embryos of Quercus serratit have been described, and it has been repotted that the diameter of fruits can be used as a good external indicator of those developmental stages. Therefore, the aim of this study was to determine whether the stages defined for Q. lernita could be applied to Q. suber and to characterize these stages in terms of external measurements.
Three unrelated trees from two different locations in the Community of Madrid were sampled biweekly, from middle April to middle October. The two locations, Arganda and Torrelaguna are environmentally very dissimilar. The length and diameter of the fruit (acorn plus cupule), and weight, length and diameter of the acorns were measured as putative external markers of zygotic embryo development. Measurements were taken from a total number of 632 fruits in different stage of development.
A graphic description of the Q. suber embryo development, which is quite similar to that of Q. serried, is showed. The stages previously defined by other authors are applied to cork oak, establishing ranges of sizes and weights for each of them. Acorns were of less than 36 mg, 4 rnm length and 3 mm diameter when the embryos were in the lower Limit of the "cotyledonary stage". Below these measures, embryos were in globular stages or they were not yet initiated. Cork oak zygotic embryos are fully developed when acorns reach 270 mg and 9 mm diameter, in average. Unlike the reported for Q. sert-ata, the correlations between length of both fruits and acorns with embryo weight were better than with diameters. However the best correlations were obtained with acorn weight that can be considered a good marker to predict embryo development in cork oak.
