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Key Characters (key + character)

Distribution by Scientific Domains

Life Sciences	100%

Selected Abstracts

Notes on South American Valerianaceae II

FEDDES REPERTORIUM, Issue 5-6 2004
F. Weberling Professor em.
Entre ValerianapotopensisBriq., descripta para Bolivia, y Valeriana humahuacensisBorsini, descripta para Jujuy, la provincia contigua de la Argentina, no se han encontrado características morfológicas para distinguir ambas especies, por eso éstas estarían unidas bajo del nombre ValerianapotopensisBriq. Por otra parte Valeriana bolivianaBritton y Valeriana bangianaGraebn., serían según Graebner (1906) dos especies distintas, pero no dió caracteres seguros para diferen-ciarlas. En este trabajo se observa que la forma de los frutos de los materiales tomados como tipo y paratipos es diferente, frutos ovados, como descripto para V. boliviana, se observan en unos paratipos, también se ven frutos ancho-ovados con un margen grueso, pero los del lectotipo V. boliviana (Rusby 871 NY) tienen un contorno casi circular como una lenteja, con un margen tenue, casi membranoso como los del lectotipo de V. bangiana (Bang 2415 G). Ni los caracteres vegetativos ni los caracteres de los frutos serían suficientes para poder distinguir V. bangianaGraebn. 1906 de V. bolivianaBritton 1891 como especies separadas. Se observa también que Valeriana variabilisGraebn. sería una forma de Valeriana warburgiiGraebn. La primera especie solo se distinguiría por caracteres poco manifiestos como el indumento de los frutos y los pelos frecuentemente se pierden durante de la maduración de los mismos, estos caracteres no serían suficientes para separar las dos especies. Por lo tanto se considera una nueva combinación, Valeriana warburgiiGraebn. subsp. variabilis(Graebn.) Weberling stat. nov. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) ValerianapotopensisBriq., described from Bolivia, and Valeriana humahuacensisBorsini, described from Jujuy, the neighbouring province of Argentina, cannot be distinguished by reliable distinctive characters. This applies especially to the indument of the fruits, since the fruits of Valeriana often become increasingly glabrescent in advanced stages of development, with the mature fruits being completely bald. Therefore both species should be united under the older name ValerianapotopensisBriq. According to Graebner (1906) Valeriana bangianaGraebn., is to be regarded as separate species, differing from Valeriana bolivianaBritton by its vigorous densely foliated stem, a character cer-tainly insufficient for a reliable identification. The fruits of V. boliviana are described as "ovatis", which is confirmed by the para-type material of the Mandon collections. In the paratypes the fruits were found to be lanceolate-ovate (Rusby872) or broadly ovate with prominent nerves and a thickened solid margin (Rusby875). However, the fruits of the holotype Rusby 871 (Fig. 12a, b) present a different shape: compressed fruits of nearly circular outline, with a broad flattened some-what membraneous marginal ring. The same form of fruits, although considerably larger, was found in the type material of Valeriana bangiana. Because of the overlapping of the vegetative characters as well as the forms of the fruits V. bangianaGraebn. 1906 cannot be clearly separated from V. bolivianaBritton 1891, and is included into this species. Valeriana warburgiiGraebn. and V. variabilisGraebn. too cannot be separated at species level because of over-lapping characters. Again the indumentum of the fruits is apparently according to several authors the best key character, but is not at all reliable. However, the outline of the fruits shows some differences. Therefore V. variabilis is included into V. warburgii as follows: V. warburgiiGraebn. subsp. variabilis(Graebn.) Weberling stat. nov. [source]

Bursaphelenchus species in conifers in Europe: distribution and morphological relationships

EPPO BULLETIN, Issue 2 2001
H. Braasch
The morphological relationship between European Bursaphelenchus species living in conifers was studied in order to provide key characters for their taxonomic identification. Several species have been newly described or recorded in Europe during the past few years and were morphologically investigated. Among the 28 conifer-inhabiting European species, four groups can be distinguished from each other by the number of lateral incisures, number and position of anal papillae of males and presence and size of a vulval flap of females. Two groups, each containing just one species show two and six lateral lines, respectively, whereas most Bursaphelenchus species belong to two groups, possessing either three or four incisures. Each of the last two groups can be divided into three subgroups, which can be differentiated by spicule shape, number and position of caudal papillae, presence and size of a vulval flap and some other features. A fifth group includes species with unclear group affiliation due to insufficient knowledge of their morphology. The B. xylophilus group (B. xylophilus, B. mucronatus, B. fraudulentus) with four lateral lines, unique spicule shape and characteristic position of the caudal papillae can clearly be differentiated from all other groups by morphology, also using only light microscopy. Within this group, B. xylophilus can clearly be differentiated morphologically from the other species, provided that adult specimens of both sexes are found and also provided that the round-tailed form of the species remains the only form present, as in Europe. Figures showing the important identification features of spicule shape and female tail shape are given for 28 species. A table shows the complete range of the most important morphometric measurements of these species. Data on the occurrence, host range and, as far as known, the vectors of these species were collected throughout Europe and references are given for each record. [source]

95 Development of macroalgal (seaweed) taxonomic keys utilizing digital & media technology

JOURNAL OF PHYCOLOGY, Issue 2003
R. L. Lehman
Digital, user-friendly seaweed identification keys and instructional materials can provide information that allows students and researchers to enhance and improve marine field and ecological studies by including macroalgae. In much of the scientific literature, the seaweeds are only characterized to division (red, green, and brown), sometimes to genus, and very rarely to species; so there is clearly a need for a reference that facilitates the identification of the seaweeds. Many of the problems occur because of the lack of user-friendly identification keys. However, it is not necessary to be an expert to identify seaweeds as many of the key characteristics used in their identification can be ascertained with the naked eye, a hand lens and an inexpensive microscope. What is needed is an identification guide that uses and displays important characters and identification structures visually (both macroscopic and microscopic) so that research scientists, students, teachers and the general public will be able to identify the seaweeds with confidence. We are using Lucid Professional software to construct digital keys for the identification of macroalgae from the Texas Coastal Bend. The advantages include: 1) key characters along with descriptions and images for specific macroalgae may be chosen from a geographic area of choice, 2) the user may evaluate the characters in any order and difficult or uncertain characters may be ignored, 3) descriptive pages of images, definitions, video clips and illustrations may be included for each taxon, and 4) the key can be displayed as a website or packaged as a CD to be used with laptop computers in the field. [source]

Why does some pollen lack apertures?

BOTANICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 1 2007
A review of inaperturate pollen in eudicots
Apertures are key characters of pollen grains with systematic importance in angiosperms. They function as sites for pollen tube exit, water uptake, transfer of recognition substances and accommodation of volume changes. Not all pollen has apertures; inaperturate pollen (lacking obvious apertures) characterizes many angiosperm groups, especially in early divergent angiosperms and monocots, but also eudicots. In order to expand our knowledge of the systematic distribution, possible functional significance and development of inaperturate pollen in angiosperms, this review focuses on inaperturate and cryptoaperturate (with hidden apertures) pollen in the large eudicot clade, which comprises about 75% of present-day angiosperm species. It includes new TEM observations of inaperturate pollen from four exemplar taxa selected from different parts of the eudicot phylogeny. Two categories of inaperturate (including cryptoaperturate) pollen occur in eudicots. (1) Sterile attractant or feeding pollen associated with functional dioecy has evolved iteratively at least six times in conjunction with complex breeding systems in the core eudicots. (2) Fertile pollen has evolved numerous times independently throughout eudicots, though generally in a relatively small number of individual taxa. Notable exceptions are the petaliferous crotonoid Euphorbiaceae s.s., in which fertile inaperturate pollen occurs in c. 1500 species, and two subfamilies of Apocynaceae s.l. (Secamonoideae and Asclepiadoideae) with c. 2500 species with fertile inaperturate pollen in pollinia. Fertile inaperturate pollen is sometimes (but not always) associated with an aquatic habit, parasitism, insectivory, heterostyly, anemophily or pollinia. Most fertile inaperturate pollen has a thin exine, or the exine is largely restricted to isolated components (muri, protuberances, subunits) separated by thinner areas which probably function as apertures. In cryptoaperturate pollen, the aperture is covered by continuous exine which probably has a protective function, similar to an operculum. Developmentally, inaperturate pollen is not associated with any particular tetrad type or meiotic spindle orientation (unlike some apertures) due to the absence of a colpal shield of endoplasmic reticulum or other organelles and hence is independent of microsporogenesis type. The lack of a colpal shield during the tetrad stage of development permits complete deposition of first primexine and then exine around each microspore, possibly mediated by the action of the DEX1 protein. © 2007 The Linnean Society of London, Botanical Journal of the Linnean Society, 2007, 155, 29,48. [source]