scholarly journals Intraspecific habitat adaptation: How the germinability of herbaceous plant seeds change due to environmental conditions in West African savannas

2019 ◽  
Vol 22 ◽  
pp. 36-42
Author(s):  
Susanna E. Schmidt-Groh ◽  
Markus Bernhardt-Römermann ◽  
Adjima Thiombiano ◽  
Karen Hahn
Keyword(s):  
Life Cycle ◽  
Environmental Factors ◽  
Environmental Conditions ◽  
Early Life ◽  
Community Dynamics ◽  
Germination Rate ◽  
Intraspecific Variability ◽  
Life Cycle Stage ◽  
West African ◽  
Herbaceous Plant

Knowledge about the herbaceous layer in relation to environmental factors in West African savannas is still scarce. Early life-cycle events like germination of the herbaceous species are of special interest, as these stages can play critical roles in establishing of the plants and determine population and community dynamics. We aim to assess intraspecific differences in the germinability of herbaceous savanna species with respect to environmental conditions to reveal adaptations in this early life cycle stage. The study was conducted in the Sudanian savanna of Burkina Faso in West Africa. We collected seeds of two annual herbs (Chamaecrista mimosoides, Spermacoce stachydea) along a climatic gradient from different habitats and land use types and conducted germination experiments under equal conditions in climate chambers. For both species several environmental factors showed a significant impact on the germination rates. While higher precipitation caused an increase in the germination rate only for S. stachydea, habitat conditions had a significant influence for both species. Intermediate habitats with balanced soil moisture caused an enhancement of the germination success. Moreover shrub cover had a positive effect on the germinability of C. mimosoides, whereas the germinability of S. stachydea decreased due to an increasing herbaceous cover. The study showed that certain environmental factors are able to modify the intraspecific variability of the germinability trait, which might affect the establishment of the species populations.

scholarly journals Differences in acid-base regulation of haploid and diploid life-cycle stages of Coccolithus braarudii and their consequences for the sensitivity towards ocean acidification

2020 ◽  
Vol 2 (7A) ◽  
Author(s):  
Dorothee Kottmeier ◽  
Abdesslam Chrachri ◽  
Gerald Langer ◽  
Glen Wheeler ◽  
Colin Brownlee
Keyword(s):  
Life Cycle ◽  
Ocean Acidification ◽  
Environmental Conditions ◽  
Life Cycle Stage ◽  
Acid Base ◽  
Proton Channels ◽  
Voltage Gated ◽  
Life Cycle Stages ◽  
H Channels ◽  
Scanning Electron

Coccolithophores are calcifying microalgae that carry characteristic calcite platelets (coccoliths) on their surfaces. Most coccolithophore species exhibit diploid and haploid life cycle stages, each adjusted to different environmental conditions. The diploid life cycle stage of the coccolithophore C. braarudii is heavily calcifying with calcification rates that exceed the rates of photosynthesis. Haploid life-cycle stages are often weakly calcifying, generating significantly less H+ from the intracellular calcification reaction. We show how these different cellular “H+ burdens” require substantially different physiological molecular strategies to regulate intracellular pH under changing environmental conditions. Voltage-gated H+ channels (Hv) have been shown to play a role in the release of H+ in the diploid life cycle previously (Taylor et al. 2011). Combining scanning electron microscopy, electrophysiology, gene expression approaches and physiological measurements, we here show a direct link between the function of proton channels and coccolith formation of the diploid but not the haploid life-cycle stage. Our data also indicate how the different mechanisms for acid-base regulation of the diploid and haploid life-cycle stages may result in different sensitivities towards ocean acidification.

Effects of Environmental Factors on Seed Germination and Emergence of Smutgrass (Sporobolus indicus) Varieties

Weed Science ◽  
2012 ◽  
Vol 60 (4) ◽  
pp. 558-563 ◽  
Author(s):  
Neha Rana ◽  
Barton J. Wilder ◽  
Brent A. Sellers ◽  
Jason A. Ferrell ◽  
Gregory E. MacDonald
Keyword(s):  
Seed Germination ◽  
Environmental Factors ◽  
Environmental Conditions ◽  
Germination Rate ◽  
Warm Season ◽  
Soil Surface ◽  
Moisture Stress ◽  
Tropical Asia ◽  
Wide Range ◽  
Germination Experiments

Smutgrass is an invasive warm-season perennial bunch-type grass native to tropical Asia. The two varieties of smutgrass prevalent in Florida are small smutgrass and giant smutgrass. Laboratory seed germination experiments were conducted on both smutgrass varieties to determine the effect of various environmental factors on germination and emergence. The average germination rate for both varieties was 88% at 30/20 C day/night temperatures. Seed germination for both varieties was greater under simulated temperature flux than at constant temperatures. Seed of both varieties germinated at four simulated Florida temperature fluxes (22/11, 27/15, 33/24, and 29/19 C day/night), although the germination of small smutgrass and giant smutgrass was reduced at 33/24 and 22/11 C, respectively. Germination of small and giant smutgrass under dark conditions was 27 and 53%, respectively. Both smutgrass varieties germinated over a wide range of pH values. Small and giant smutgrass germination was inhibited at water potentials below −0.2 MPa and when small smutgrass seed was placed below the soil surface. Emergence of giant smutgrass seed did not occur below 3 cm. Both smutgrass varieties germinated over a broad range of environmental conditions, indicating their capability of year-round germination; however, germination is only likely to occur under field conditions during the summer growing season when rainfall is prevalent. These results indicate that both species have the ability to germinate over a wide range of environmental conditions but that germination is inhibited by moisture stress and depth of burial. Considering that giant smutgrass prefers higher temperatures than small smutgrass, the advent of rainfall from June through September is conducive for germination. Practices that focus on the germination pattern of smutgrass could lead to better long-term management of smutgrass in Florida.

scholarly journals IPO boards of directors and firm performance: Threshold firms and governance theory boundaries

2007 ◽  
Vol 4 (2) ◽  
pp. 162-169
Author(s):  
Suzanne M. Carter ◽  
James H. Davis ◽  
Charles R. Young
Keyword(s):  
Life Cycle ◽  
Firm Performance ◽  
Early Life ◽  
Boards Of Directors ◽  
Past Research ◽  
Life Cycle Stage ◽  
Board Structure ◽  
Board Effectiveness ◽  
Start Up ◽  
And Behavior

Past research examining the influence of boards of directors on firm performance has acknowledged, but typically failed to account for, the early life cycle stage of the firm. This study analyzes the effectiveness of board structure and behavior on firm performance in the early stages of the life-cycle for start-up IPO firms. Results suggest that the life-cycle of the firm is an important contextual variable to include when determining board effectiveness

scholarly journals Regional environmental controllers influence continental scale soil carbon stocks and future carbon dynamics

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Daniel Ruiz Potma Gonçalves ◽  
Umakant Mishra ◽  
Skye Wills ◽  
Sagar Gautam
Keyword(s):  
Environmental Factors ◽  
Land Cover ◽  
Environmental Conditions ◽  
Climate Feedback ◽  
Soil Types ◽  
Climatic Data ◽  
Earth System ◽  
Land Cover Types ◽  
Continental Scale ◽  
Soc Stocks

AbstractUnderstanding the influence of environmental factors on soil organic carbon (SOC) is critical for quantifying and reducing the uncertainty in carbon climate feedback projections under changing environmental conditions. We explored the effect of climatic variables, land cover types, topographic attributes, soil types and bedrock geology on SOC stocks of top 1 m depth across conterminous United States (US) ecoregions. Using 4559 soil profile observations and high-resolution data of environmental factors, we identified dominant environmental controllers of SOC stocks in 21 US ecoregions using geographically weighted regression. We used projected climatic data of SSP126 and SSP585 scenarios from GFDL-ESM 4 Earth System Model of Coupled Model Intercomparison Project phase 6 to predict SOC stock changes across continental US between 2030 and 2100. Both baseline and predicted changes in SOC stocks were compared with SOC stocks represented in GFDL-ESM4 projections. Among 56 environmental predictors, we found 12 as dominant controllers across all ecoregions. The adjusted geospatial model with the 12 environmental controllers showed an R2 of 0.48 in testing dataset. Higher precipitation and lower temperatures were associated with higher levels of SOC stocks in majority of ecoregions. Changes in land cover types (vegetation properties) was important in drier ecosystem as North American deserts, whereas soil types and topography were more important in American prairies. Wetlands of the Everglades was highly sensitive to projected temperature changes. The SOC stocks did not change under SSP126 until 2100, however SOC stocks decreased up to 21% under SSP585. Our results, based on environmental controllers of SOC stocks, help to predict impacts of changing environmental conditions on SOC stocks more reliably and may reduce uncertainties found in both, geospatial and Earth System Models. In addition, the description of different environmental controllers for US ecoregions can help to describe the scope and importance of global and local models.

Emerging investigator series: interacting effects of environmental factors on Daphnia magna removal of Escherichia coli from wastewater

2021 ◽  
Vol 7 (4) ◽  
pp. 726-738
Author(s):  
Seyyed M. H. Abtahi ◽  
Ojaswi Aryal ◽  
Niveen S. Ismail
Keyword(s):  
Escherichia Coli ◽  
Environmental Factors ◽  
Daphnia Magna ◽  
Environmental Conditions ◽  
E Coli

Zooplankton can significantly impact E. coli inactivation in wastewater, but inactivation rates are dependent on environmental conditions.

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