<?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></contributors><titles><title><style face="normal" font="default" size="100%">LIGNOTUBER ONTOGENY IN THE CORK-OAK (QUERCUS-SUBER, FAGACEAE) .1. LATE EMBRYO</style></title><secondary-title><style face="normal" font="default" size="100%">AMERICAN JOURNAL OF BOTANY</style></secondary-title></titles><dates><year><style  face="normal" font="default" size="100%">1993</style></year></dates><publisher><style face="normal" font="default" size="100%">BOTANICAL SOC AMER INC</style></publisher><pub-location><style face="normal" font="default" size="100%">OHIO STATE UNIV-DEPT BOTANY 1735 NEIL AVE, COLUMBUS, OH 43210</style></pub-location><volume><style face="normal" font="default" size="100%">80</style></volume><pages><style face="normal" font="default" size="100%">172-181</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Changes at the cotyledonary node of the cork-oak (Quercus suber L.) were examined during the embryo maturation phase using light microscopy and scanning electron microscopy techniques. During the maturation phase the embryo axis elongates by diffuse growth, the apical meristem forms the first leaf primordia, and the radicle meristem remains inactive. The primary axis of the embryo bears, axillary to the cotyledons, in the range of five to seven pairs of lateral buds at differing stages of development. Two or three pairs of these buds are visible, occurring on the upper unfused portion of the embryonic axis, while the remaining buds are hidden by the fused cotyledonary tissues. Lateral buds develop from clusters of cells in the peripheral meristem forming a shell zone delimiting the bud meristem. Lateral buds do not undergo much development until germination begins. The results are discussed with reference to the possible role of the cotyledonary node as the source of the lignotuber in the cork-oak.</style></abstract><notes><style face="normal" font="default" size="100%">APS</style></notes><research-notes><style face="normal" font="default" size="100%">APS</style></research-notes></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors></contributors><titles><title><style face="normal" font="default" size="100%">LIGNOTUBER ONTOGENY IN THE CORK-OAK (QUERCUS-SUBER, FAGACEAE) .2. GERMINATION AND YOUNG SEEDLING</style></title><secondary-title><style face="normal" font="default" size="100%">AMERICAN JOURNAL OF BOTANY</style></secondary-title></titles><dates><year><style  face="normal" font="default" size="100%">1993</style></year></dates><publisher><style face="normal" font="default" size="100%">BOTANICAL SOC AMER INC</style></publisher><pub-location><style face="normal" font="default" size="100%">OHIO STATE UNIV-DEPT BOTANY 1735 NEIL AVE, COLUMBUS, OH 43210</style></pub-location><volume><style face="normal" font="default" size="100%">80</style></volume><pages><style face="normal" font="default" size="100%">182-191</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Lignotuber origin was studied in cork-oak seedlings at different stages from germination to seedling establishment. By the time germination is completed, the seedling consists of an elongated embryonic axis between the developing first shoot and first root. The cotyledonary insertion divides the axis in two portions: an apical portion, visible between the cotyledonary petioles; and an enlarged lower portion in which the cotyledonary tissues are fused with the axis. Several histological changes take place in the fused portion: initial vascular differentiation occurs; parenchymatous cells contain large amounts of starch; and the vascular cambium and periderm are formed early. In the cotyledonary stage seedlings, axillary buds of the cotyledonary node develop. Buds in the unfused upper portion remain single and form a short stalk and laminar scales. Buds in the fused portion, hidden by the cotyledonary tissues, form hypertrophied scales and multiply to form bud clusters. As development proceeds, the root-shoot transition region becomes woody, bearing both individual buds as well as bud clusters and concentrating food reserves. All of the transition region in the cork-oak is considered equivalent to a lignotuber.</style></abstract><notes><style face="normal" font="default" size="100%">Keys: APS</style></notes><research-notes><style face="normal" font="default" size="100%">Keys: APS</style></research-notes></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors></contributors><titles><title><style face="normal" font="default" size="100%">Anatomía y caracterización del sistema radicular del alcornoque</style></title><secondary-title><style face="normal" font="default" size="100%">SCIENTIA gerundensis</style></secondary-title></titles><dates><year><style  face="normal" font="default" size="100%">1992</style></year></dates><volume><style face="normal" font="default" size="100%">18</style></volume><pages><style face="normal" font="default" size="100%">39-51</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">In this paper we describe the root system of a mature cork oak (Quercus suber L). The roots were excavated by hand methods, seccioned and weighed. Large sections were described anatomically and sections smaller than 10 mm of diameter by histological tecniques. The root system components were distributed into central root system (CRS) and peripheral root system (PRS). The CRS was located at the base of the tree and embraced an area of 1'5 m and a depth of 60 cm; it consisted of the root crown, thick horizontal or descending roots and thin roots. The PRS extended in a circle of 12 m in diameier. In the PRS, the thick roots were distributed more laxly and the thin roots predominated. At their basal portion, the descending roots were eccentric and eliptic and rapidly forked into two or more small- diameter branches. Grafting between root axes was frequent. The horizontal roots were perpendicular to the tree axis, they were quite circular and kept thickness more or less constant since they forked. Large-diameter root tips, white coloured were observed and their primary structure described. Neither on the root crown nor at the base of the roots, lateral huds were observed.</style></abstract></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors></contributors><titles><title><style face="normal" font="default" size="100%">The stomata of the cork-oak, Quercus suber. An ultrastructural approach</style></title><secondary-title><style face="normal" font="default" size="100%">Nordic Journal of Botany</style></secondary-title></titles><dates><year><style  face="normal" font="default" size="100%">1991</style></year></dates><publisher><style face="normal" font="default" size="100%">Blackwell Publishing Ltd</style></publisher><volume><style face="normal" font="default" size="100%">11</style></volume><pages><style face="normal" font="default" size="100%">205-212</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">In the evergreen leaves of Quercus suber, stomata play a major role in adaptation to drought and temperature stress. The leaf is of zygostomic type and has about 430 stomata per square milimeter of abaxial leaf surface. The stomatal complex is of the anomocytic type. The guard cells protrude from the epidermal plane. The guard cell nucleus contains heterochromatin in small granules. The guard cell cytoplasm is characterised by a large number of well developed mitochondria, amyloplasts with stroma and grana, and a well developed cytoskeleton with a cortical array of microtubules oriented pa railed to the slit axis that persist even in mature cells. Guard cell walls are asymmetrically thickened and devoid of plasmodesmata. No area of cell walls was free of cuticle or covered by a thin cuticular layer and apparently no area of limited cuticular development provides evaporation when the stomata are closed.</style></abstract></record></records></xml>