Caracteres diagnósticos foliares en táxones ibéricos de <i>Isoetes</i> L. (Isoetaceae, Pteridophyta)

Abstract

Se presenta un estudio de morfología foliar comparada en los táxones del género Isoetes que crecen en la Península Ibérica: I. durieui e I. histrix (terrestres), I. setaceum, I. velatum subsp. velatum (anfibios) e I. brochonii, I. echinosporum, I. × hickeyi, I. lacustre, I. longissimum e I. velatum subsp. asturicense (acuáticos). Se incluye también en la comparación un taxon anfibio tetraploide no descrito, relacionado morfológicamente con I. velatum, que hasta su descripción se designa provisionalmente como Isoetes sp. Se estudiaron varias colecciones ibéricas y, en el caso de algunos táxones, se incluyeron ejemplares procedentes de otras localidades de Europa y América, con el fin de contrastar los rasgos analizados. Los caracteres estudiados fueron: ornamentaciones cuticulares, modelos epidérmicos y estomas (morfología, distribución y dimensiones), contorno de las secciones transversales foliares, epidermis en corte (membrana cuticular, cutícula, ornamentaciones cuticulares), desarrollo relativo del mesofilo, presencia o ausencia y distribución del colénquima, diafragmas foliares y presencia o ausencia de protuberancias intercelulares pécticas de las células de los diafragmas (de tipo filamento). Todos los caracteres son independientes de la edad de los microfilos, de la madurez de las plantas y, en general, del hábitat, y se observan por igual en material fresco o restaurado medianteuna técnica que se propone en este trabajo.

This is a comparative study of foliar morphology of the species of Isoetes L. growing in the Iberian Península. The taxa included are /. durieui and /. histrix (terrestrial), /. setaceum, and /. velatum subsp. Velatum (amphibious), and /. brochonii, I. echinosporum, I. x hickeyi, I. lacustre, I. longissimum and /. velatum subsp. Asturicense (aquatic). Material of an undescribed amphibious tetraploid taxon related to /. velatum was also included in this study and referred as Isoetes sp. until proper description. Several Iberian collections, together with European and American specimens of some of the taxa were analyzed. Selected diagnostic characters of the microphylls are: cuticular ornamentation (striae, ridges and warts), cuticular flanges, epidermal patterns, stomata distribution and dimensions, foliar transverse sectíons outline, degree of development of the mesophyll, presence or absence, and distribution of the mechanical tissues (collenchyma), diaphragms, and presence or absence and type of intercellular pectic protuberances. All characters are stable, and do not vary with the age of the plants or the microphylls. Cuticular striae, ridges and warts, as well as stomata develop early in plantlets. Stomata present in the microphylls of two aquatic taxa (/. longissimum, I. velatum subsp. asturicense) suggest that their absence is not entirely due to influence of aquatic environment. Collenchyma occurs, also, in species growing in different habitats. Restored herbarium material proved to be as useful as fresh or fixed material, an important advantage in the case of Isoetes species, many of which grow in vulnerable áreas or are known only through herbarium specimens due to destruction of their pristine habitats.