Pollen size evolution: correlation between pollen volume and pistil length in Asteraceae

2000 ◽  
Vol 12 (6) ◽  
pp. 365-370 ◽  
Author(s):  
C. Torres
Keyword(s):  
Pollen Size ◽  
Size Evolution ◽  
Pistil Length

scholarly journals Influence of flower functionality and pollination system on the pollen size-pistil length relationship

2009 ◽  
Vol 9 (2) ◽  
pp. 75-82 ◽  
Author(s):  
Verónica Andrea Fernández ◽  
Leonardo Galetto ◽  
Julia Astegiano
Keyword(s):  
Pollen Size ◽  
Pollination System ◽  
Length Relationship ◽  
Pistil Length

Investigation of irradiation-induced nucleation processes in silicon and germanium

1995 ◽  
Vol 53 ◽  
pp. 224-225
Author(s):  
Harry A. Atwater ◽  
C.M. Yang ◽  
K.V. Shcheglov
Keyword(s):  
Room Temperature ◽  
Crystal Size ◽  
Initial Distribution ◽  
Engineering Control ◽  
Size Evolution ◽  
Silicon And Germanium ◽  
Ge Quantum Dot ◽  
And Control ◽  
Germanium Quantum Dots ◽  
Kinetics Of

Studies of the initial stages of nucleation of silicon and germanium have yielded insights that point the way to achievement of engineering control over crystal size evolution at the nanometer scale. In addition to their importance in understanding fundamental issues in nucleation, these studies are relevant to efforts to (i) control the size distributions of silicon and germanium “quantum dots𠇍, which will in turn enable control of the optical properties of these materials, (ii) and control the kinetics of crystallization of amorphous silicon and germanium films on amorphous insulating substrates so as to, e.g., produce crystalline grains of essentially arbitrary size.Ge quantum dot nanocrystals with average sizes between 2 nm and 9 nm were formed by room temperature ion implantation into SiO2, followed by precipitation during thermal anneals at temperatures between 30°C and 1200°C[1]. Surprisingly, it was found that Ge nanocrystal nucleation occurs at room temperature as shown in Fig. 1, and that subsequent microstructural evolution occurred via coarsening of the initial distribution.

Evolution of Angiosperm Pollen: 8. Lamiids

2020 ◽  
Vol 105 (3) ◽  
pp. 323-376
Author(s):  
Li-E Yang ◽  
Lu Lu ◽  
Kevin S. Burgess ◽  
Hong Wang ◽  
De-Zhu Li
Keyword(s):  
Maximum Likelihood ◽  
Pollen Morphology ◽  
Pollen Size ◽  
State Transitions ◽  
Character State ◽  
Evolutionary Mechanisms ◽  
Pollen Characters ◽  
Exine Ornamentation ◽  
Shape Class ◽  
Pollen Character

Lamiids, a clade composed of approximately 15% of all flowering plants, contains more than 50,000 species dispersed across 49 families and eight orders (APG IV, 2016). This paper is the eighth in a series that analyzes pollen characters across angiosperms. We reconstructed a maximum likelihood tree based on the most recent phylogenetic studies for the Lamiids, comprising 150 terminal genera (including six outgroups) and covering all eight orders and 49 families within the clade. To illustrate pollen diversity across the Lamiids, pollen grains from 22 species (22 genera in 14 families) were imaged under light, scanning, and transmission electron microscopy. Eighteen pollen characters that were documented from previous publications, websites, and our new observations were coded and optimized onto the reconstructed phylogenetic tree using Fitch parsimony, maximum likelihood, and hierarchical Bayesian analysis. Pollen morphology of the Lamiids is highly diverse, particularly in shape class, pollen size, aperture number, endoaperture shape, supratectal element shape, and tectum sculpture. In addition, some genera show relatively high infrageneric pollen variation within the Lamiids: i.e., Coffea L., Jacquemontia Choisy, Justicia L., Pedicularis L., Psychotria L. nom. cons., Sesamum L., Stachytarpheta Vahl, and Veronica L. The plesiomorphic states for 16 pollen characters were inferred unambiguously, and 10 of them displayed consistent plesiomorphic states under all optimization methods. Seventy-one lineages at or above the family level are characterized by pollen character state transitions. We identified diagnostic character states for monophyletic clades and explored palynological evidence to shed light on unresolved relationships. For example, palynological evidence supports the monophyly of Garryales and Metteniusaceae, and sister relationships between Icacinaceae and Oncothecaceae, as well as between Vahliales and Solanales. The evolutionary patterns of pollen morphology found in this study reconfirm several previously postulated evolutionary trends, which include an increase in aperture number, a transition from equatorially arranged apertures to globally distributed ones, and an increase in exine ornamentation complexity. Furthermore, there is a significant correlation between pollen characters and a number of ecological factors, e.g., pollen size and pollination type, pollen ornamentation and pollination type, and shape class and plant growth form. Our results provide insight into the ecological, environmental, and evolutionary mechanisms driving pollen character state changes in the Lamiids.

PATTERNS OF GENOME SIZE EVOLUTION IN TETRAODONTIFORM FISHES

Evolution ◽  
2001 ◽  
Vol 55 (11) ◽  
pp. 2363 ◽  
Author(s):  
Elizabeth L. Brainerd ◽  
Sandra S. Slutz ◽  
Edward K. Hall ◽  
Randall W. Phillis
Keyword(s):  
Genome Size ◽  
Genome Size Evolution ◽  
Size Evolution

scholarly journals Grain Size Evolution and Mechanical Properties of Nb, V–Nb, and Ti–Nb Boron Type S1100QL Steels

Metals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 492
Author(s):  
Jan Foder ◽  
Jaka Burja ◽  
Grega Klančnik
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Grain Size ◽  
Hot Forging ◽  
Size Control ◽  
High Strength ◽  
Fatigue Properties ◽  
Titanium Addition ◽  
Austenite Grain Size ◽  
Size Evolution

Titanium additions are often used for boron factor and primary austenite grain size control in boron high- and ultra-high-strength alloys. Due to the risk of formation of coarse TiN during solidification the addition of titanium is limited in respect to nitrogen. The risk of coarse nitrides working as non-metallic inclusions formed in the last solidification front can degrade fatigue properties and weldability of the final product. In the presented study three microalloying systems with minor additions were tested, two without any titanium addition, to evaluate grain size evolution and mechanical properties with pre-defined as-cast, hot forging, hot rolling, and off-line heat-treatment strategy to meet demands for S1100QL steel. Microstructure evolution from hot-forged to final martensitic microstructure was observed, continuous cooling transformation diagrams of non-deformed austenite were constructed for off-line heat treatment, and the mechanical properties of Nb and V–Nb were compared to Ti–Nb microalloying system with a limited titanium addition. Using the parameters in the laboratory environment all three micro-alloying systems can provide needed mechanical properties, especially the Ti–Nb system can be successfully replaced with V–Nb having the highest response in tensile properties and still obtaining satisfying toughness of 27 J at –40 °C using Charpy V-notch samples.

scholarly journals Different environmental variables predict body and brain size evolution in Homo

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Manuel Will ◽  
Mario Krapp ◽  
Jay T. Stock ◽  
Andrea Manica
Keyword(s):  
Environmental Factors ◽  
Cognitive Abilities ◽  
Net Primary Productivity ◽  
Brain Size ◽  
Environmental Influence ◽  
Size Variation ◽  
Evolutionary Pattern ◽  
Statistical Framework ◽  
Size Evolution ◽  
Major Predictor

AbstractIncreasing body and brain size constitutes a key macro-evolutionary pattern in the hominin lineage, yet the mechanisms behind these changes remain debated. Hypothesized drivers include environmental, demographic, social, dietary, and technological factors. Here we test the influence of environmental factors on the evolution of body and brain size in the genus Homo over the last one million years using a large fossil dataset combined with global paleoclimatic reconstructions and formalized hypotheses tested in a quantitative statistical framework. We identify temperature as a major predictor of body size variation within Homo, in accordance with Bergmann’s rule. In contrast, net primary productivity of environments and long-term variability in precipitation correlate with brain size but explain low amounts of the observed variation. These associations are likely due to an indirect environmental influence on cognitive abilities and extinction probabilities. Most environmental factors that we test do not correspond with body and brain size evolution, pointing towards complex scenarios which underlie the evolution of key biological characteristics in later Homo.

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