Endodermis foliares en el género Isoetes L. (Isoetaceae).

Abstract

RESUMEN. Endodermis foliares en el género Isoetes L. (Isoetaceae). La presencia y naturaleza de la endodermis en microfilos de 18 taxones de Isoetes se puso de manifiesto con técnicas microquímicas de coloración con TBO y mediante fluorescencia intrínseca (autofluorescencia). Las especies estudiadas son: I. adspersa, I. andina, I. boliviensis, I. boryana, I.brochonii, I. durieui, I. echinospora, I.engelmanii, I. histrix, I. lacustris, I. lechleri, I. longissima, I. malinverniana, I. melanopoda, I. setacea, I. storkii, I. velata subsp. velata, I. velata subsp. asturicense. Desde el punto de vista morfológico se reconocen tres tipos de endodermis, que coexisten en la misma hoja. Una endodermis primaria con bandas de Caspary, que se desarrolla inicialmente rodeando los canales intrastelares, pero que evolucionaría hacia endodermis secundaria (con engrosamientos «en U»), ya que éste es el tipo que se encuentra en torno de los canales intrastelares en microfilos de todas las especies estudiadas. También se forma una endodermis secundaria (con engrosamientos «en U»), parcial o completa, rodeando las cámaras aeríferas, en todas las especies estudiadas. Las especies que crecen a mayor altura sobre el nivel del mar pueden desarrollar en esta zona una endodermis terciaria (con engrosamientos «en O»). La endodermis de las cámaras aeríferas está menos desarrollada o desaparece en la porción del microfilo que se encuentra hundida en el sustrato, no así la endodermis de los canales intrastelares. La función reguladora del flujo de agua y metabolitos entre el haz vascular y el mesofilo explicaría tanto la presencia como la especialización de estas capas en microfilos sujetos a estrés hídrico.Palabras clave. Isoetes, microfilos, anatomía, endodermis, estrés hídricoABSTRACT. Foliar endodermis in genus Isoetes L. (Isoetaceae). Microchemical analysis with TBO, and intrinsic fluorescence (autofluorescence) were used to detect the presence and occurrence of endodermis in microphylls of 18 taxa of genus Isoetes (I. adspersa, I. andina, I. boliviensis, I. boryana, I.brochonii, I. durieui, I. echinospora, I.engelmanii, I. histrix, I. lacustris, I. lechleri, I. longissima, I. malinverniana, I. melanopoda, I. setacea, I. storkii, I. velata subsp. velata, I. velata subsp. asturicense). From a morphological point of view, three known endodermal types can be found in the microphylls, and they also coexist in the same leaf. Casparian strips are developed in a primary endodermis that surrounds intrastelar canals, which probably progress to a secondary endodermis (with «U thickenings»), since microphylls of all studied species bear secondary, suberized and lignified endodermis in every intrastelar canal. A secondary or even a tertiary lignified endodermis develops in mesophyll cells of the central area of the leaf next to the air chambers; secondary endodermis occurs in all studied species, and tertiary endodermis was found only in species that live in bogs, moors or seasonal swamps, at the higher altitudes in the Southamerican Andes. Endodermis of the air chambers become thinner or disappears in the buried part of the microphylls, while the endodermis of intrastelar canals does not change. Comments are made on the adaptive significance of specialized endodermal layer in aquatic, amphibious and terrestrial species. The participation of the endodermis in the regulation of the loss of water and metabolites from the vascular system to the mesophyll could be an explanation of the presence of these layers.Key words. Isoetes, microphylls, anatomy, endodermis, hydric stress

CARACTERES DIAGNÓSTICOS FOLIARES EN ISOETES (PTERIDOPHYTA, ISOETACEAE)1,2

“…Hall (1971) sugirió que los canales llevan agua y no aire. Esta es una interesante afirmación en relación con lo anterior, ya que el mayor número de canales intrastelares en plantas anfibias o terrestres podría relacionarse con la necesidad obvia en éstas de evitar que los tejidos vasculares se inunden periód-icamente, una función a la que contribuye la presencia de endodermis en los canales (Rolleri & Prada, 2004).…”

Anatomical studies of Brazilian Amazonian Isoëtes species: inferences on habitat adaptation

“…Previous studies showed that several anatomical traits of Isoëtes leaves, such as the number of interstellar canals, the shape of the translacunar diaphragm cells, the presence of intercellular pectic protuberances, peripheral fibrous strands, stomata, cuticular ornamentations, and the sporangium epidermis coloration, have diagnostic value (Pfeiffer 1922;Hall 1971;Prada 1979Prada , 1983Takamiya et al 1997;Kott & Britton 1985;Hickey 1986;Taylor & Hickey 1992). Fluorescence and scanning microscopy techniques were used to document and categorize the endoderm of the interstellar canals and the aerenchyma lacunae (Romeo et al 2000;Rolleri & Prada 2004) and the intercellular pectic protuberances (Prada & Rolleri 2003;Rolleri & Prada 2005). In addition to qualitative traits, micro-morphometric leaf parameters have also been identified as taxonomically important (Budke et al 2005;Rolleri & Prada 2007).…”

A new species of Isoetes (Isoetaceae) from Turkey, with a study of microphyll intercellular pectic protuberances and their potential taxonomic value

“…Literature on Isoetes and keys to the species of the genus normally rely on a few characters, mostly related to habit, plant size, corm lobing, velum cover, spore size and ornamentation, and more recently, chromosome number. Based on previous studies made on Isoetes (Hall, 1971;Marsden, 1976;Prada, 1979;Prada & Rolleri, 2003;Rolleri & Prada, 2004; C. H. Rolleri & C. Prada, unpubl. data) several additional foliar characters are used here to identify taxa in the genus. These characters are: cuticular ornamentation, presence or absence of cuticular pegs, types of margin, epidermal patterns of microphylls, stomata, transverse sections of microphylls, number and distribution of collenchymatous strands in the mesophyll, presence and types of intercellular pectic protuberances (IPP) of the cells of the translacunar diaphragms, presence of a partial or complete foliar endodermis at the air chambers and intrastellar canals of the leaves (Rolleri & Prada, 2004), and epidermal patterns of sporangium adaxial wall.…”

“…Literature on Isoetes and keys to the species of the genus normally rely on a few characters, mostly related to habit, plant size, corm lobing, velum cover, spore size and ornamentation, and more recently, chromosome number. Based on previous studies made on Isoetes (Hall, 1971; Marsden, 1976; Prada, 1979; Prada & Rolleri, 2003; Rolleri & Prada, 2004; C. H. Rolleri & C. Prada, unpubl. data) several additional foliar characters are used here to identify taxa in the genus.…”

“…data) several additional foliar characters are used here to identify taxa in the genus. These characters are: cuticular ornamentation, presence or absence of cuticular pegs, types of margin, epidermal patterns of microphylls, stomata, transverse sections of microphylls, number and distribution of collenchymatous strands in the mesophyll, presence and types of intercellular pectic protuberances (IPP) of the cells of the translacunar diaphragms, presence of a partial or complete foliar endodermis at the air chambers and intrastellar canals of the leaves (Rolleri & Prada, 2004), and epidermal patterns of sporangium adaxial wall. These characters are included in the description of the new taxon.…”