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Anatomy and Morphology |
2Unitat de Biologia Vegetal, Departament de Ciències Ambientals, Universitat de Girona, Campus de Montilivi s/n 17071 Girona, Spain; 3Unitat de Biologia Cel.lular, Departament de Biologia, Universitat de Girona, Campus de Montilivi s/n 17071 Girona, Spain
Anatomical changes at the cotyledonary node from the embryo to the seedling stage in Quercus coccifera, Q. ilex, and Q. humilis were investigated by light and scanning electron microscopy techniques. Mature embryos of Q. humilis possess 23 pairs of leaf primordia and a pair of cotyledonary buds, whereas in Q. coccifera and Q. ilex there are two incipient primordia, and cotyledonary buds are not observed until 1 wk after germination. In all three species the cotyledonary buds multiply, forming bud clusters, and a vascular connection is well established within 56 wk after germination. As development proceeds, the cotyledonary region becomes woody, but buds, which are exogenous in origin, never become embedded in the periderm. In comparison with Q. suber, another native Mediterranean Basin oak, the cotyledonary node is short and axillary buds are not present below the insertion of cotyledons. In addition, starch accumulation in the cotyledonary region is not observed from histological analysis in the three oaks. Therefore, in Q. coccifera, Q. ilex, and Q. humilis seedlings the cotyledonary node can be considered to be an important regenerative structure enabling them to resprout after the elimination of the shoot above the cotyledons, despite the absence of a lignotuberous structure.
Key Words: cotyledonary bud cotyledonary node lignotuber Quercus coccifera Quercus humilis Quercus ilex Quercus suber sprout
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