El objetivo de este trabajo fue evaluar caracteres anatómicos foliares que contribuyan a una mejor comprensión de la relación planta-ambiente y al desarrollo de tecnologías para el aprovechamiento sustentable y conservación de los bosques de esta región. Para ello se aplicaron técnicas histológicas convencionales sobre hojas de ejemplares de 36 especies recolectadas en la región chaqueña húmeda. Se determinaron densidades por mm-2 de células epidérmicas, estomas y tricomas, tipos de mesofilo, tipo y distribución de los tejidos vascular y de sostén. La mayoría de los árboles de la región en estudio presentan hojas hipostomáticas con mesofilo dorsiventral, elevada densidad de células epidérmicas (4000-7000/mm-2), una densidad intermedia de estomas (300-500/mm-2) y baja densidad de tricomas (< 35/mm-2). La comparación con los caracteres anatómicos foliares de los arbustos y árboles de las Provincias Biogeográficas Paranaense, de las Yungas y Chaqueña permite concluir que los rasgos más variables son la distribución de estomas y tipo de mesofilo. Las hojas xeromórficas son anfistomáticas, equifaciales y las mesomórficas son hipostomáticas, bifaciales. En el Distrito Chaqueño Oriental las hojas son predominantemente meso-xeromórficas, ya que a sus rasgos mesomórficos se suman otros xeromórficos como elevada densidad de células epidérmicas y abundante tejido esclerenquimático.
[D-Leu1]MC-LR and MC-LR, two microcystins differing in one amino acid, constitute a sanitary and environmental problem owing to their frequent and concomitant presence in water bodies of the Americas and their association with human intoxication during recreational exposure to cyanobacterial bloom. Present in reservoirs used for irrigation as well, they can generate problems in the development of crops such as Phaseolus vulgaris, of nutritional and economic interest to the region. Although numerous works address the toxic effects of MC-LR, information on the toxicity of [D-Leu1]MC-LR is limited. Our objective was to study the toxic effects of [D-Leu1]MC-LR and MC-LR (3.5 µg/ml) on P. vulgaris after a single contact at the imbibition stage. Our findings indicate that 10 days post treatment, [D-Leu1]MC-LR generates morphological and physiological alterations more pronounced than those caused by MC-LR. In addition to the alterations produced by [D-Leu1]MC-LR in the development of seedlings and the structure of the leaves, roots and stems, we also found alterations in leaf stomatal density and conductivity, a longer delay in the phototropic response and a decrease in the maximum curvature angles achieved with respect to that observed for MC-LR. Our findings indicate that these alterations are linked to the greater inhibition of phosphatase activity generated by [D-Leu1]MC-LR, rather than to oxidative damage. We observed that 30 days after treatment with MC-LR, plants presented better development and recovery than those treated with [D-Leu1]MC-LR. Further studies are required on [D-Leu1]MC-LR and MC-LR toxicity and their underlying mechanisms of action.
El presente trabajo se desarrolló en el marco del proyecto “Anatomía de los órganos vegetativos con propiedades medicinales de Espermatófitas rioplatenses. I. Hierbas terrestres”. En esta oportunidad realizamos el estudio de las características micrográficas foliares de 62 especies pertenecientes a 24 familias. El objetivo fue generar una clave dicotómica para identificar los taxones a partir de las hojas, ya sea que este material se encuentre al estado entero o fragmentado y brindar información en un cuadro comparativo de los parámetros cuantitativos, los cuales son importantes herramientas en el control de calidad farmacognóstica. Se estudiaron hojas maduras frescas y de ejemplares de herbario empleando técnicas histológicas convencionales (“peeling”, impronta, diafanización, cortes transversales). Se practicaron métodos microquímicos para la identificación de almidón, mucílagos, sustancias lipofílicas y mirosina. Las principales diferencias se encontraron en la forma de las células epidérmicas, distribución y tipo de estomas, tipos de tricomas, mesofilo foliar, características de la vena media e índices estomático y de pilosidad. La presencia de una endodermis conspicua; los diferentes tipos de cristales y reservorios secretores internos (células, cavidades y conductos) contribuyeron a la elaboración de una clave de diferenciación.
Senecio L. s.str. is the largest genus in the tribe Senecioneae (Asteraceae) and it has been commonly characterized by its truncate, penicillate stylar tips, separated stigmatic lines, and stamens usually with ecaudate anther bases and balusterform filament collar. A micromorphological study was carried out to determine if South American species of Senecio s.str. present these diagnostic micromorphological characters, as a contribution towards a circumscription of this genus supported by morphology. The study included 72 South American Senecio species from eight sections and 16 series, as well as species from six other genera of subtribe Senecioninae (Delairea, Dendrophorbium, Dendrosenecio, Graphistylis, Lomanthus, Pentacalia), three genera of subtribe Tussilagininae (Aequatorium, Nordenstamia, Roldana), and one of subtribe Brachyglottidinae (Acrisione). The studied characters include: style branches (stigmatic surface, and apices), anthers (filament collar, bases, and appendages), as well as pollen features (shape, size, and sculpture). Analyses of these characters suggested that Senecio s.str. can be defined only by the presence of balusterform filament collars, which are present in 61 out of the 72 studied Senecio s.str. species (vs. cylindrical collar in remaining species). The genera Graphistylis and Delairea also show this trait, however, Graphistylis presents some microcharacters (e.g. “banded” stigmatic surface) that are rather infrequently found in Senecio s.str. Senecio grandis showed cylindrical collars and sagittate anther bases and should be excluded from the genus. The other microcharacters analyzed appeared to be taxonomically uninformative, since their predominant states were found in Senecio s.str. as well as in other genera of Senecioneae.
These developments resulted in bifurcation in the styles of Asteraceae, with each branch face having a different function, and it is suggested here as a mechanism that promoted outcrossing, which in turn led to the great diversification in the family.
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