%0 Journal Article
%T Las Est¨ªpulas como Caracteres Sistem¨¢ticos Confiables The stipules as reliable systematical characters
%A Focko Weberling
%J Bolet¨ªn de la Sociedad Argentina de Bot¨¢nica
%D 2006
%I Sociedad Argentina de Bot¨¢nica
%X Generalmente la presencia o ausencia de est¨ªpulas es importante en la caracterizaci¨®n de familias de dicotiled¨®neas y en la estimaci¨®n de sus relaciones de parentesco. Esto significa, que las est¨ªpulas en general son estructuras muy constantes. Tan solo debemos recordar las Rubiaceae con sus est¨ªpulas interfoliares, que en casos de material vegetativo pueden permitir la identificaci¨®n como miembros de esta familia, o, en otro caso la distinci¨®n entre Rosaceae y Ranuculaceae en claves anal¨ªticas.  Cu¨¢l es la causa de esta constancia?  Esta cualidad tambi¨¦n se refiere a est¨ªpulas rudimentarias?  Cu¨¢les son las relaciones morfol¨®gicas entre formas diferentes de est¨ªpulas y sus funciones?  C¨®mo se pueden distinguir est¨ªpulas de otros ap¨¦ndices basales de las hojas, que no son equivalentes? En la mayor¨ªa de los casos la aplicaci¨®n de los m¨¦todos de la morfolog¨ªa comparada con la observaci¨®n cr¨ªtica de sus reglas no solamente puede llevar a la respuesta de las preguntas, sino que en combinaci¨®n con m¨¦todos gen¨¦ticos tambi¨¦n, probablemente, puede abrir nuevos aspectos en cuanto a la formaci¨®n de estructuras vegetales. Stipules are reckoned among the most constant vegetative characters in Dicotyledons. They are formed as marginal outgrowths of the leaf base, at the border of the two integral parts of the leaf, the leaf base ("Unterblatt") and the "Oberblatt", the distal part of the leaf, which forms the lamina and the petiole. Their ontogeny is characterized by an early, often extremely early, appearance and a following precursive development. Therefore the stipules can temporarily exceed the other parts of the leaf, which enables them to function as protecting organs for the terminal bud of a shoot and even for the same leaf. The protecting function is not the only function of stipules. They can also work as assimilation organs or can be developed as spines or glands. In pinnate leaves with basipetal segmentation the stipules often have finished their growth whereas the segmentation of the lamina still is progressing. This confirms the opinion of Eichler (1861) who regarded "Unterblatt" (leaf base) and "Oberblatt" (the distal part of the leaf) as relatively independent components of the leaf. The early appearance of the stipules in the ontogeny of the leaf certainly is responsible for their high constancy and consequently their high systematic value. Form and position of the stipules can vary according to the "principle of variable proportions". In such cases, however, the study of their ontogeny can prove the morphological identity and elucidate the relations
%K Aparici¨®n temprana
%K Desarrollo precoz
%K Aur¨ªculas
%K L¨®bulos de la vaina pseudoest¨ªpulas
%K Reducci¨®n
%K Early appearance
%K Precursive growth
%K Auricules
%K Vaginal lobes
%K Pseudostipules
%K Rudimentation
%U http://www.scielo.org.ar/scielo.php?script=sci_arttext&pid=S1851-23722006000100012