Abstract
The microspores ofIsoetes escondidensis, I. gardneriana, I. herzogii, I. pedersenii, andI. savatieri were analyzed with transmission and scanning electron microscopy. The selected species were found to be representative of the diversity found in 24 taxa previously studied that grow in southern South America. The sporoderm is similar in the five types and is composed, from the outside to the inside, of perispore, para-exospore, exospore, and endospore. InI. escondidensis, I. gardneriana, I. herzogii, andI. savatieri, the perispore is lacunose, whereas inI. pedersenii, it is camerate. The para-exospore is formed of large superimposed and fused bars, which are more numerous and thicker in immature spores. The exospore shows uniform characteristics and a strongly contrasted cover. It has pluristratified zones on both sides of the aperture. The presence of radial rodlets between the para-exospore and exospore and in the supra-apertural chamber is described here for the first time. The endospore has a fibrillate or reticulate structure, or both structures may be present. A boundary within the fibrillate endospore is evident, which might be related to stages of deposition. The surface characteristics are formed by either the middle and outer strata of the perispore or elements on the outer surface, as inI. escondidensis. The characteristics of the microspore surface and of the perispore structure provide characteristics useful for systematic purposes at the infrageneric level
Resumen
Las microsporas deIsoetes escondidensis, I. gardneriana, I. herzogii, I. pedersenii yI. savatieri fueron analizadas con microscopios electrónicos de transmisión y barrido. Las especies seleccionadas son representativas de la diversidad encontrada en los 24 taxa que crecen en el Cono Sur de América Meridional previamente estudiados. La compositión de la esporodermis es similar en los cinco tipos, diferenciándose desde afuera hacia adentro, perisporio, para-exosporio, exosporio y endosporio. EnI. escondidensis, I. gardneriana, I. herzogii yI. savatieri el perisporio es lacunoso, mientras que enI. pedersenii es camerado. El para-exosporio está constituido por barras largas, superpuestas y fusionadas cuyo número y espesor es mayor en esporas inmaduras. El exosporio presenta características uniformes y posee una cubierta fuertemente contrastada con zonas pluriestratificadas a ambos lados de la abertura. Se cita aquí por primera vez la presencia de varillitas entre el para-exosporio y el exosporio y en la cámara supra-abertural. El endosporio es fibrilar o reticulado. En el fibrilar se distinguen dos capas que tendrían relatión con las etapas de depositación. Las características superficiales están definidas por el perisporio, específicamente por los estratos medio, externo o por elementos por encima de este, como enI. escondidensis. Las características de la superficie de las microsporas y la estructura del perisporio, podrían ser útiles para fines sistemáticos a nivel infra-genérico
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Macluf, C.C., Morbelli, M.A. & Giudice, G.E. Microspore morphology ofIsoetes species (lycophyta) from southern South America. Part II. TEM analysis of some selected types. Bot. Rev 72, 135–152 (2006). https://doi.org/10.1663/0006-8101(2006)72[135:MMOISL]2.0.CO;2
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DOI: https://doi.org/10.1663/0006-8101(2006)72[135:MMOISL]2.0.CO;2