scholarly journals On the lack of adaptation in the Tristichaceœ and Podostemaceœ

1914 ◽  
Vol 87 (598) ◽  
pp. 532-550 ◽  
Keyword(s):  
Life History ◽  
Morphological Structure ◽  
Living Condition ◽  
Flowering Plants ◽  
Natural Habitats ◽  
Dead Material ◽  
Dry Seasons ◽  
Great Uniformity ◽  
High Degree

With the exception of some of the parasitic orders, such as the Balanophoraceœ , there are probably no families of flowering plants—one might almost include flowerless—which are so completely transformed from the average or mesophytic type of the phanerogams into types which are so completely unique and peculiar, as the Tristichaceæ and still more the Podostemaceæ. Nor are there any in which, with such very great uniformity in the conditions of life, there is such remarkable variety in the morphological structure. The structure of the orders, or rather of their members, being unique, and the conditions under which they live being also unique, it has been taken for granted that the former is in a high degree adapted to the latter, the flat thallus-like expansions of stem or root being looked upon as admirably suited to the rushing water in which they live. So long as we were almost completely ignorant of the actual living plants, and content with dead material collected mainly in the dry seasons, this was all very well, but now that for 17 years I have devoted much attention to these plants,* have studied them in the living condition in their natural habitats in India, Ceylon, and Brazil, have followed them from germination right through their life-history, and in other ways become absolutely familiar with them, and as a result of all this have arrived at diametrically opposite conclusions, it will repay us to examine into the question in some detail.

scholarly journals Proteogenomic Insights into the Physiology of Marine, Sulfate-Reducing, Filamentous Desulfonema limicola and Desulfonema magnum

2021 ◽  
Vol 31 (1) ◽  
pp. 36-56
Author(s):  
Vanessa Schnaars ◽  
Lars Wöhlbrand ◽  
Sabine Scheve ◽  
Christina Hinrichs ◽  
Richard Reinhardt ◽  
...  
Keyword(s):  
Energy Metabolism ◽  
Gene Clusters ◽  
Transport Systems ◽  
Natural Habitats ◽  
Sulfate Reducing ◽  
Type Iv ◽  
Aromatic Compound Degradation ◽  
High Degree ◽  
Reducing Bacteria ◽  
Gliding Movement

The genus Desulfonema belongs to the deltaproteobacterial family Desulfobacteraceae and comprises marine, sulfate-reducing bacteria that form filaments and move by gliding. This study reports on the complete, manually annotated genomes of Dn. limicola 5ac10T (6.91 Mbp; 6,207 CDS) and Dn. magnum 4be13T (8.03 Mbp; 9,970 CDS), integrated with substrate-specific proteome profiles (8 vs. 11). The richness in mobile genetic elements is shared with other Desulfobacteraceae members, corroborating horizontal gene transfer as major driver in shaping the genomes of this family. The catabolic networks of Dn. limicola and Dn. magnum have the following general characteristics: 98 versus 145 genes assigned (having genomic shares of 1.7 vs. 2.2%), 92.5 versus 89.7% proteomic coverage, and scattered gene clusters for substrate degradation and energy metabolism. The Dn. magnum typifying capacity for aromatic compound degradation (e.g., p-cresol, 3-phenylpropionate) requires 48 genes organized in operon-like structures (87.7% proteomic coverage; no homologs in Dn. limicola). The protein complements for aliphatic compound degradation, central pathways, and energy metabolism are highly similar between both genomes and were identified to a large extent (69–96%). The differential protein profiles revealed a high degree of substrate-specificity for peripheral reaction sequences (forming central intermediates), agreeing with the high number of sensory/regulatory proteins predicted for both strains. By contrast, central pathways and modules of the energy metabolism were constitutively formed under the tested substrate conditions. In accord with their natural habitats that are subject to fluctuating changes of physicochemical parameters, both Desulfonema strains are well equipped to cope with various stress conditions. Next to superoxide dismutase and catalase also desulfoferredoxin and rubredoxin oxidoreductase are formed to counter exposure to molecular oxygen. A variety of proteases and chaperones were detected that function in maintaining cellular homeostasis upon heat or cold shock. Furthermore, glycine betaine/proline betaine transport systems can respond to hyperosmotic stress. Gliding movement probably relies on twitching motility via type-IV pili or adventurous motility. Taken together, this proteogenomic study demonstrates the adaptability of Dn. limicola and Dn. magnum to its dynamic habitats by means of flexible catabolism and extensive stress response capacities.

scholarly journals Differing effects of size and lifestyle on bone structure in mammals

2020 ◽  
Author(s):  
Eli Amson ◽  
Faysal Bibi
Keyword(s):  
Life History ◽  
Body Size ◽  
Bone Structure ◽  
Lumbar Vertebra ◽  
Vertebrate Evolution ◽  
Functional Factors ◽  
Degree Of Convergence ◽  
High Degree

AbstractThe skeleton is involved in most aspects of vertebrate life history. Previous macroevolutionary analyses have shown that structural, historical, and functional factors influence the gross morphology of bone. The inner structure of bone has, however, received comparatively little attention. Here we address this gap in our understanding of vertebrate evolution by quantifying bone structure in appendicular and axial elements (humerus and mid-lumbar vertebra) across therian mammals (placentals + marsupials). Our sampling captures all transitions to aerial, fully aquatic, and subterranean lifestyles in extant mammal clades. We found that mammalian inner bone structure is highly disparate. We show that vertebral structure mostly correlates with body size, but not lifestyle, while the opposite is true for humeral structure. The latter also shows a high degree of convergence among the clades that have acquired specialised lifestyles. Our results suggest that radically different extrinsic constraints can apply to bone structure in different skeletal elements.

Some Observations on the biology of the Root-gall Nematode, Anguillulina Radicicola (Greeff, 1872)

1932 ◽  
Vol 10 (1) ◽  
pp. 33-44 ◽  
Author(s):  
T. Goodey
Keyword(s):  
Life History ◽  
Living Condition ◽  
Poa Annua ◽  
Infective Stage ◽  
Northern Sweden ◽  
Important Data ◽  
Set Up

In a paper published in 1925, the writer described the anatomy of the adults of this parasite and amplified Schøyen's account of it. At the same time it was shown that infective material derived from Elymus arenarius could give rise to galls on the roots of barley and Poa annua. Kemner (1930) has quite recently shown experimentally that the parasite from barley can set up galls on E. arenarius and presented important data on the agricultural significance of the parasite in northern Sweden. Detailed information as to which is infective stage of the parasite and on its life-history have so far been lacking and in order to remedy this omission the writer made a number of observations and carried out certain cultural experiments during 1927 and in the months of July, August and September 1931. These latter were made possible by the arrival during July of a good supply of galled roots of Elymus arenarius received in a living condition.

RELIABILITY OF FLOWERING AS AN INDICATOR OF WINTER SURVIVAL IN RED CLOVER

1963 ◽  
Vol 43 (3) ◽  
pp. 386-389 ◽  
Author(s):  
Dale Smith
Keyword(s):  
Selection Criterion ◽  
Red Clover ◽  
Flowering Plants ◽  
Flowering Plant ◽  
First Year ◽  
Plant Type ◽  
Plant Populations ◽  
Flowering Response ◽  
High Degree

Flowering response of first-year individual plants of nine varieties of red clover was studied at Arlington, Wisconsin. Plant populations of varieties with high winterhardiness had high percentages of non-flowering plants. Winterkilling of plant types increased progressively from non-flowering Type 1 to profuse flowering Type 5.Highly significant correlations were obtained between per cent winterkilling during the first winter with per cent non-flowering plant Type 1 (r = −0.90 and −0.95 during 2 years), per cent of flowering plant Type 5 (r = +0.92 and +0.80), and the total per cent of non-flowering plants (r = −0.90 and −0.94). Flowering response can be used with a high degree of reliability in establishing the probable persistence of new strains relative to standard varieties and as a selection criterion for hardy plants.

scholarly journals Biomass components of Pennisetum purpureum cv. Roxo managed at different growth ages and seasons

2018 ◽  
Vol 19 (1) ◽  
pp. 11-22 ◽  
Author(s):  
Theyson Duarte MARANHÃO ◽  
Magno José Duarte CÂNDIDO ◽  
Marcos Neves LOPES ◽  
Roberto Cláudio Fernandes Franco POMPEU ◽  
Maria Socorro de Souza CARNEIRO ◽  
...  
Keyword(s):  
Linear Response ◽  
Leaf Blade ◽  
Pennisetum Purpureum ◽  
Maximum Point ◽  
Area Index ◽  
Average Value ◽  
Randomized Design ◽  
Dead Material ◽  
Biomass Components ◽  
Dry Seasons

SUMMARY This study was carried out aiming to evaluate the biomass components of elephant grass cv. Roxo at seven growth ages, during rainy, transition and dry seasons. A completely randomized design was adopted with a split plot arrangement over time. The treatments consisted of seven growth ages (9, 18, 27, 36, 45, 54 and 63) and three seasons (rainy, transition and dry). The variables green forage biomass, dead forage biomass, green stem biomass and green leaf blade biomass showed positive linear responses to age and had their magnitude influenced by the evaluated seasons. The live/dead material ratio showed a decreasing linear response as a function of age. The leaf blade/stem ratio showed a negative linear adjustment in the rainy season, reaching a critical value of 1.0 at 59 days, and it showed a quadratic adjustment in the transition season, with the maximum point at 27.53 days; however, this ratio was not influenced by age in the dry season, revealing an average value of 2.22 ± 0.27. The canopy height and leaf area index showed a positive linear response to age in the three seasons. Tiller population density showed quadratic behaviour for age, with maximum estimated values of 134 and 110 til. m-2 at 31.24 and 37.40 days in the rainy and dry seasons, respectively. Rainfall seasonality influences the magnitude of the daily increase of the distinct biomass components of Pennisetum purpureum cv. Roxo.

Solvent, LICL, and Temperature Effects on the Morphological Structure and Electronic Properties of Polyaniline

1995 ◽  
Vol 413 ◽  
Author(s):  
Marie Angelopoulos ◽  
Yun-Hsin Liao ◽  
Bruce Furman ◽  
Teresita Graham
Keyword(s):  
Hydrogen Bonding ◽  
Surface Structure ◽  
Morphological Changes ◽  
Base Material ◽  
Morphological Structure ◽  
Gel Permeation Chromatography ◽  
The Individual ◽  
High Degree ◽  
Pani Base ◽  
Different Levels

ABSTRACTExtensive gel permeation chromatography coupled with surface structure measurements clearly indicate that polyaniline (pani) base has a tendency to aggregate as a result of interchain hydrogen-bonding. The aggregation is present in the solid state powder; the extent of aggregation is found to be significantly dependent on the synthetic conditions. Pani base powders having a high degree of aggregation have significantly reduced solubility. The degree of aggregation of pani base in solution is found to be dependent on the solvent, concentration, and temperature. As the solvent becomes a better solvent for the base material, the less aggregated is the structure. Solvents which can strongly interact with the polymer disrupt the aggregation. In addition, salts such as LiCl which complex the polymer via a “pseudo-doping” process, also disrupt the internal pani hydrogen-bonding and deaggregate the polymer. As the polymer is deaggregated to different levels by a solvent or by LiCl, the individual chains can better be solvated and thus a conformational change also occurs. The chains adapt a more expanded coil type of conformation. The degree of expansion depends on the solvation power of the solvent. As the level of deaggregation and subsequent chain expansion increases, a significant red shift is observed in the λmaximum of the exciton absorbance and the surface structure of the polymer becomes smoother. It is found that the LiCl induced morphological changes results in increased conductivity upon doping pani base with a protonic acid.

Some life-history consequences of modular construction in plants

1986 ◽  
Vol 313 (1159) ◽  
pp. 31-51 ◽  
Keyword(s):  
Life History ◽  
Clonal Plants ◽  
Modular Construction ◽  
Death Rates ◽  
Relative Growth Rates ◽  
Apical Meristems ◽  
Modular Units ◽  
Single Shoot ◽  
Dead Material ◽  
Weak Constraints

The nature and life-history consequences of modular construction in plants are discussed with particular reference to growth, reproduction and survival. Plants grow by the iteration of modular units and as a consequence growth can be described in terms of the population dynamics of these structural units. Changes in size, whether positive or negative, depend on the birth and death rates of modules; however, if the births continue to exceed the deaths, plants then have the capability of attaining enormous sizes, especially if they are clonal. The population nature of plant growth also means that plants of the same age may show large variation in individual size if individuals differ in their relative growth rates. Correlations between age and size are often, therefore, very weak. Constraints on the allocation of resources accumulated during growth have important implications for the reproductive schedules of plants, but the analysis of constraint functions has so far revealed little about the actual detail of these schedules. All the meristems of semelparous plants are involved in or die at reproduction and as a consequence death of the genet follows reproduction. For iteroparous plants, however, there are fundamental differences between the reproductive schedules of plants with a single shoot module and those with many shoot modules. The former demonstrate a relatively constant rate of reproduction from year to year following maturity whereas the latter show a continual increase in fecundity with size and age. The reproductive schedules of clonal plants are further discussed in relation to the allocation of meristems to either growth or reproduction. The pattern of mortality is examined at both the level of the module and the genet. Particular attention is focused on the survival and senescence of leaves and shoots; there is no equivalent regular shedding of organs in unitary organisms. Whereas genet senescence and death are coincident with shoot module death in semelparous plants, there is no evident relation between them in iteroparous plants. The life span of the genet reflects the birth and death rates of its modules and both aclonal and clonal plants that are iteroparous may achieve considerable longevity. The longevity of aclonal plants often seems to be restricted by the accumulation of dead material and the problems of being large. Clonal plants are, in contrast, potentially immortal. It is questionable whether the genets of iteroparous plants show senescence as defined for unitary organisms since there is no separation of germ plasm from soma and since apical meristems do not appear to senesce. Insofar as they retain the capacity for rejuvenescence from apical meristems, genets of modular organisms do not senesce; it is only the constituent organs that show senescence, death and decay.

scholarly journals Exploring the Relationships between Mutation Rates, Life History, Genome Size, Environment, and Species Richness in Flowering Plants

2015 ◽  
Vol 185 (4) ◽  
pp. 507-524 ◽  
Author(s):  
Lindell Bromham ◽  
Xia Hua ◽  
Robert Lanfear ◽  
Peter F. Cowman
Keyword(s):  
Life History ◽  
Species Richness ◽  
Genome Size ◽  
Flowering Plants ◽  
Mutation Rates

On the reliability of unreliable information

2016 ◽  
Vol 17 (1) ◽  
pp. 1-25 ◽  
Author(s):  
Dominic Mitchell ◽  
Joanna J. Bryson ◽  
Paul Rauwolf ◽  
Gordon P.D. Ingram
Keyword(s):  
Life History ◽  
Spatial Model ◽  
Value Of Information ◽  
Transmission Error ◽  
Relative Importance ◽  
Direct Experience ◽  
High Degree ◽  
The Impact ◽  
Source Of Information

Abstract When individuals learn from what others tell them, the information is subject to transmission error that does not arise in learning from direct experience. Yet evidence shows that humans consistently prefer this apparently more unreliable source of information. We examine the effect this preference has in cases where the information concerns a judgment on others’ behaviour and is used to establish cooperation in a society. We present a spatial model confirming that cooperation can be sustained by gossip containing a high degree of uncertainty. Accuracy alone does not predict the value of information in evolutionary terms; relevance, the impact of information on behavioural outcomes, must also be considered. We then show that once relevance is incorporated as a criterion, second-hand information can no longer be discounted on the basis of its poor fidelity alone. Finally we show that the relative importance of accuracy and relevance depends on factors of life history and demography.

Ordering towards disorder

2019 ◽  
Vol 43 (4) ◽  
pp. 800-849
Author(s):  
Lukas Denk
Keyword(s):  
Layered Structure ◽  
Morphological Structure ◽  
Language Family ◽  
Distributional Properties ◽  
Morphological Theory ◽  
Semantic Relevance ◽  
Verbal Morphological Structure ◽  
The Stability ◽  
High Degree ◽  
Inflectional Affixes

Abstract In Athabascan languages, verbal morphological structure does not follow the cross-linguistically more common and stable ‘layered’ order: derivational and lexical affixes are not necessarily closer to the stem than inflectional affixes. While the emergence of the Athabascan order is understandable through different layers of grammaticalization (Mithun 2011), the question of why this order is relatively stable in the language family has not yet been satisfactorily answered. The distributional properties of cognate Athabascan morphemes reveal historical tendencies for fusion and reordering that suggest that affixes remain in or change their position depending on the semantic relevance to other affixes, not necessarily to the stem alone, as Bybee’s (1985) morphological theory would predict. An additional factor for the stability of non-layered structure of morphemes is the high degree of semantic generality found in affixes between the stem and other lexical and derivational affixes.

Sign in / Sign up

Export Citation Format

Share Document