Percurrent proliferations in fungi, algae, and mosses

1971 ◽  
Vol 49 (2) ◽  
pp. 215-231 ◽  
Author(s):  
S. J. Hughes
Keyword(s):  
Red Algae ◽  
Common Phenomenon ◽  
Reproductive Structures

The production of new reproductive structures at the apex of successive percurrent proliferations is a common phenomenon in fungi. Successive sporangia and conidia in Phycomycetes, successive asci, conidia, phialides, and possibly 'gemmae' in Ascomycetes, and successive probasidia, basidia, and apparently urediniospores in Basidiomycetes, can be produced in this way. Examples of these are given from published accounts and some personal observations. Successive reproductive structures of various kinds are also formed on percurrent proliferations in 'green,' brown, and red algae. In the red algae successive antheridia can develop within empty ones by this method; it is concluded that such antheridia are not phialides. Successive gemmae in some mosses are formed terminally on percurrent proliferations.

scholarly journals The evolution of desiccation tolerance in angiosperm plants: a rare yet common phenomenon

2013 ◽  
Vol 40 (4) ◽  
pp. 315 ◽  
Author(s):  
Donald F. Gaff ◽  
Melvin Oliver
Keyword(s):  
Desiccation Tolerance ◽  
Seed Plants ◽  
Common Phenomenon ◽  
Vegetative Tissue ◽  
Vegetative Cells ◽  
Evolutionary Path ◽  
Reproductive Structures ◽  
Drought Avoidance ◽  
Angiosperm Species ◽  
Derivatives Of

In a minute proportion of angiosperm species, rehydrating foliage can revive from airdryness or even from equilibration with air of ~0% RH. Such desiccation tolerance is known from vegetative cells of some species of algae and of major groups close to the evolutionary path of the angiosperms. It is also found in the reproductive structures of some algae, moss spores and probably the aerial spores of other terrestrial cryptogamic taxa. The occurrence of desiccation tolerance in the seed plants is overwhelmingly in the aerial reproductive structures; the pollen and seed embryos. Spatially and temporally, pollen and embryos are close ontogenetic derivatives of the angiosperm microspores and megaspores respectively. This suggests that the desiccation tolerance of pollen and embryos derives from the desiccation tolerance of the spores of antecedent taxa and that the basic pollen/embryo mechanism of desiccation tolerance has eventually become expressed also in the vegetative tissue of certain angiosperm species whose drought avoidance is inadequate in micro-habitats that suffer extremely xeric episodes. The protective compounds and processes that contribute to desiccation tolerance in angiosperms are found in the modern groups related to the evolutionary path leading to the angiosperms and are also present in the algae and in the cyanobacteria. The mechanism of desiccation tolerance in the angiosperms thus appears to have its origins in algal ancestors and possibly in the endosymbiotic cyanobacteria-related progenitor of chloroplasts and the bacteria-related progenitor of mitochondria. The mechanism may involve the regulation and timing of the accumulation of protective compounds and of other contributing substances and processes.

A morphological study of the red alga Leveillea jungermannioides

1968 ◽  
Vol 46 (12) ◽  
pp. 1543-1554 ◽  
Author(s):  
Robert F. Scagel ◽  
Mitsuo Chihara
Keyword(s):  
Red Algae ◽  
Morphological Study ◽  
Systematic Position ◽  
Red Alga ◽  
Morphological Evidence ◽  
Reproductive Structures

A detailed description of the juvenile thallus and male, female, and tetrasporangiate reproductive structures is given for the red alga Leveillea jungermannioides (Hering et Martens) Harvey (subfamily Polyzonieae, family Rhodomelaceae). Morphological evidence is presented to support the systematic position of the genus Leveillea and to indicate affinities with the genera Polyzonia and Dasyclonium (= Euzonielld) in the same subfamily of this group of red algae.

Open discussion

1982 ◽  
Vol 99 ◽  
pp. 605-613
Author(s):  
P. S. Conti
Keyword(s):  
Buenos Aires ◽  
Large Mass ◽  
List Type ◽  
Common Phenomenon ◽  
Open Discussion ◽  
The Stability ◽  
Ring Nebulae

Conti: One of the main conclusions of the Wolf-Rayet symposium in Buenos Aires was that Wolf-Rayet stars are evolutionary products of massive objects. Some questions:–Do hot helium-rich stars, that are not Wolf-Rayet stars, exist?–What about the stability of helium rich stars of large mass? We know a helium rich star of ∼40 MO. Has the stability something to do with the wind?–Ring nebulae and bubbles : this seems to be a much more common phenomenon than we thought of some years age.–What is the origin of the subtypes? This is important to find a possible matching of scenarios to subtypes.

Freeze substitution fixation of fungal reproductive structures and spores

1989 ◽  
Vol 47 ◽  
pp. 990-991
Author(s):  
C. W. Mims ◽  
E. A. Richardson
Keyword(s):  
Plant Pathogens ◽  
Freeze Substitution ◽  
Uranyl Acetate ◽  
Chemical Fixation ◽  
Dialysis Membrane ◽  
Razor Blade ◽  
Thin Sections ◽  
Reproductive Structures ◽  
Dry Down ◽  
Diamond Knife

The advantages of freeze substitution fixation over conventional chemical fixation for preservation of ultrastructural details in fungi have been discussed by various authors. As most ascomycetes, basidiomycetes and deuteromycetes do not fix well using conventional chemical fixation protocols, freeze substitution has attracted the attention of many individuals interested in fungal ultrastructure. Thus far most workers using this technique on fungi have concentrated on thin walled somatic hyphae. However, in our laboratory we have experimented with the use of freeze substitution on a variety of fungal reproductive structures and spores with promising results.Here we present data on freeze substituted samples of sporangia of the zygomycete Umbellopsis vinacea, basidia of Exobasidium camelliae var. gracilis, developing teliospores of the smut Sporisorium sorghi, germinating teliospores of the rust Gymnosporangium clavipes, germinating conidia of the deuteromycete Cercosporidium personatum, and developing ascospores of Ascodesmis nigricans.Spores of G. clavipes and C. personatum were deposited on moist pieces of sterile dialysis membrane where they hydrated and germinated. Asci of A. nigricans developed on pieces of dialysis membrane lying on nutrient agar plates. U. vinacea was cultured on small pieces of agar-coated wire. In the plant pathogens E. camelliae var. gracilis and S. sorghi, a razor blade was used to remove smal1 pieces of infected host issue. All samples were plunged directly into liquid propane and processed for study according to Hoch.l Samples on dialysis membrane were flat embedded. Serial thin sections were cut using a diamond knife, collected on slot grids, and allowed to dry down onto Formvar coated aluminum racks. Sections were post stained with uranyl acetate and lead citrate.

Antitumor and antifungal activities from red algae Bostrychia radicans and B. tenella (Rhodophyta)

Planta Medica ◽  
2008 ◽  
Vol 74 (09) ◽  
Author(s):  
ALL de Oliveira ◽  
R de Felício ◽  
LV Costa-Lotufo ◽  
MO de Moraes ◽  
C do Ó Pessoa ◽  
...  
Keyword(s):  
Red Algae ◽  
Antifungal Activities

Bioactive chemical constituents from the Formosan red algae Laurencia tristicha

Planta Medica ◽  
2016 ◽  
Vol 81 (S 01) ◽  
pp. S1-S381
Author(s):  
JY Chen ◽  
CY Huang ◽  
JH Sheu
Keyword(s):  
Red Algae ◽  
Chemical Constituents

INVESTIGATING ENGLISH DEPARTMENT STUDENTS’ FOREIGN LANGUAGE SPEAKING ANXIETY: A CASE STUDY IN UNIVERSITAS AIRLANGGA, INDONESIA

2020 ◽  
Vol 1 (2) ◽  
pp. 22
Author(s):  
Dyas Intan Rachmawati ◽  
Jurianto Jurianto
Keyword(s):  
Foreign Language ◽  
Significant Negative Correlation ◽  
English Department ◽  
Common Phenomenon ◽  
Speaking Anxiety ◽  
Pearson Product Moment Correlation ◽  
Efl Learners ◽  
Achievement Score ◽  
Anxiety Levels

Anxiety during a speaking performance is a common phenomenon experienced by any EFL learners, including students majoring in English. Focusing on the issue, this study investigates the correlation between students’ foreign language speaking anxiety and speaking achievement. Moreover, this study also observes the levels and the sources of the speaking anxiety among the English Department’s fifth-semester students of Universitas Airlangga. This study used the Foreign Language Speaking Anxiety Scale (FLSAS) by Öztürk and Gurbuz (2014). The FLSAS questionnaire was distributed to 114 students in order to explore the correlation between speaking anxiety and speaking achievement, the speaking anxiety levels, and the speaking anxiety sources. The data collected through questionnaire were analyzed with SPSS 25.0. Pearson Product Moment Correlation isused to determine the correlation, while descriptive statistic alanalys is isused to investigate the levels and the sources for speaking anxiety. Horwitz, Horwitzand Cope’s(1986) theory and Horwitz and Young (1991) about the source and the levels of foreign language speaking anxiety are also used in this study. This study found that there is a significant negative correlation between speaking anxiety levels and speaking achievement. This means the higher the speaking anxiety they experience, the lower the achievement score they get. Most of the students have moderate levels of speaking anxiety, which is mainly due to the fear of negative evaluation.This study indicates that although the EFL learners are often exposed to English, they still experience speaking anxiety. These findings suggest that the lecturers should be more aware of students’ anxiety and use strategies that might encourage the students to speak more confidently.

Code-switching in parents’ everyday speech to bilingual infants

2020 ◽  
Author(s):  
Lena V. Kremin ◽  
Julia Alves ◽  
Adriel John Orena ◽  
Linda Polka ◽  
Krista Byers-Heinlein
Keyword(s):  
Language Acquisition ◽  
Code Switching ◽  
Common Phenomenon ◽  
English Bilingual ◽  
Audio Recordings ◽  
Bilingual Communities ◽  
Apparent Reasons ◽  
At Home

Code-switching is a common phenomenon in bilingual communities, but little is known about bilingual parents’ code-switching when speaking to their infants. In a pre-registered study, we identified instances of code-switching in day-long at-home audio recordings of 21 French–English bilingual families in Montreal, Canada, who provided recordings when their infant was 10 and 18 months old. Overall, rates of infant-directed code-switching were low, averaging 7 times per hour (6 times per 1,000 words) at 10 months and increasing to 28 times per hour (18 times per 1,000 words) at 18 months. Parents code-switched more between sentences than within a sentence; this pattern was even more pronounced when infants were 18 months than when they were 10 months. The most common apparent reasons for code-switching were to bolster their infant’s understanding and to teach vocabulary words. Combined, these results suggest that bilingual parents code-switch in ways that support successful bilingual language acquisition.

Taxonomic Treatment of the Tillandsia utriculata Complex (Bromeliaceae)

2019 ◽  
Vol 104 (2) ◽  
pp. 262-323
Author(s):  
Juan P. Pinzón ◽  
Ivón M. Ramírez-Morillo ◽  
Germán Carnevali ◽  
Walter Till ◽  
Derek Butcher ◽  
...  
Keyword(s):  
Diagnostic Characters ◽  
Taxonomic Treatment ◽  
Reproductive Structures ◽  
Taxonomic Information

The taxonomic treatment of the 18 species composing the Tillandsia utriculata L. complex s.l. is presented. A description and a diagnosis of the group are provided, as well as two artificial keys to species, each emphasizing characters from living plants or from exsiccatae, respectively. Complete taxonomic information is given, including taxonomic citation, synonymy, etymology or eponimy, description, specimens examined, phenology, nomenclatural notes, relationships and diagnostic characters, variation, ecology and distribution, together with plates of living plants and vegetative and reproductive structures, as well as maps of distribution.

Sign in / Sign up

Export Citation Format

Share Document