SummaryPolyethylene glycol (PEG) is a low-cost and advantageous embedding medium, which maintains the majority of cell contents unaltered during the embedding process. Some hard or complex plant materials are better embedded in PEG than in other usual embedding media. However, the histochemical tests for phenolics and lignins in PEG-embedded plant tissues commonly result in false negatives. We hypothesize that these false negatives should be prevented by the use of distinct fixatives, which should avoid the bonds between PEG and phenols. Novel protocols for phenolics and flavanols detection are efficiently tested, with fixation of the samples in ferrous sulfate and formalin or in caffeine and sodium benzoate, respectively. The differentiation of lignin types is possible in safranin-stained sections observed under fluorescence. The Maule's test faultlessly distinguishes syringyl-rich from guaiacyl-and hydroxyphenyl-rich lignins in PEG-embedded material under light microscopy. Current hypothesis is corroborated, that is, the adequate fixation solves the false-negative results, and the new proposed protocols fill up some gaps on the detection of phenolics and lignins. (J Histochem Cytochem 65:105-116, 2017)
The success of galling insects could be determined by synchronisation with host plant phenology and climate conditions, ensuring suitable oviposition sites for gall induction and food resources for their survival. The anatomical, histochemical and phenological synchronisation strategies between Calophya rubra (Blanchard) (Hemiptera: Psylloidea) and its host, the evergreen plant Schinus polygama (Cav.) (Cabrera) (Anacardiaceae), in the Mediterranean climate of southern Chile was evaluated and compared to that of the congeneric C. cf. duvauae (Scott) from Brazil and closely related host plant S. engleri in a subtropical climate. Anatomical, histometric, histochemical and vegetative phenology studies of the stem and galls were conducted from June 2015 to December 2016. Based on the anatomical, histometric and histochemical analysis, the conical stem gall traits imply gains over the non-galled stem toward the galling insect survival, but the maintenance of phellem, secretory ducts and pith indicate conservative developmental traits that cannot be manipulated by C. rubra. Our results indicate that the conditions of the Mediterranean climate zone limit C. rubra immature activity during unfavourable periods, probably determining a diapause period and a univoltine life cycle, which are peculiarities of the S. polygama- C. rubra system. The synchronisation between development and seasonality confers peculiarities to the S. polygama- C. rubra system in the Mediterranean climate zone.
Efecto alelopático de la invasoraWe evaluated the effect of leaves, flowers, pods and seeds of A. dealbata on the germination and early growth of these native species. Biological assays were carried out under laboratory conditions, based on aqueous extracts and the direct effect of plant material. Leaf litter prevented the germination of both species and seeds of the invasive species impeded the germination of Q. saponaria. Other plant parts from A. dealbata also induced reductions of hypocotyl and radicle lengths in the native species, reaching over 50 % in some treatment values. All plant parts caused radicle necrosis, preventing the formation of root hairs and, consequently, jeopardizing the survival possibility of the recipient species. The results show that A. dealbata can interfere with the establishment of pioneer herbaceous species in ecological succession and can also affect trees if they are reached by the invasion front.KEYWORDS: Allelochemicals, aqueous extracts, Helenium aromaticum, Quillaja saponaria, invasive plants. RESUMENLas plantas que crecen cerca o bajo el dosel de Acacia dealbata Link (Fabaceae, subfamilia: Mimosoideae), cuando esta se encuentra en el rango no nativo, sobreviven con dificultad o no lo logran, especialmente si son nativas. Este fenómeno se ha atribuido a la alelopatía; una de las estrategias utilizadas por A. dealbata para promover su proceso de invasión. Las especies nativas Quillaja saponaria Molina (arbórea) y Helenium aromaticum (Hook.) H.L. Bailey (herbácea) comparten el rango de distribución de A. dealbata en el centro-sur de Chile. El presente trabajo se realizó en la Región del Biobío y se evaluaron los efectos de hojas, flores, vainas y semillas de A. dealbata en la germinación y crecimiento temprano de las especies nativas mencionadas. Los ensayos biológicos se llevaron a cabo en condiciones de laboratorio, basados en extractos acuosos y efectos directos del material vegetal. Nuestros resultados indicaron que las hojas impidieron la germinación de ambas especies nativas, pero las semillas impidieron sólo la germinación de Q. saponaria. Otras partes de la planta de A. dealbata también indujeron fuertes reducciones de las longitudes del hipocótilo y radícula en las especies nativas, superándose el 50% en algunos tratamientos. Todas las partes de la planta causaron necrosis en la radícula, evitando la formación de pelos radicales y, por consiguiente, comprometiendo la posibilidad de supervivencia de las especies receptoras. Estos resultados muestran que A. dealbata puede interferir en el establecimiento de especies herbáceas pioneras en la sucesión ecológica y también puede afectar especies arbóreas secundarias si son alcanzadas por el frente de invasión.
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