Critical role of air and soil temperature in the development of primary and secondary physical dormancy in Albizia julibrissin (Fabaceae)

2021 ◽  
pp. 1-7
Author(s):  
Ganesh K. Jaganathan ◽  
Matthew Biddick
Keyword(s):  
Moisture Content ◽  
Critical Role ◽  
Canopy Cover ◽  
Physical Dormancy ◽  
Maternal Environment ◽  
Albizia Julibrissin ◽  
Secondary Dormancy ◽  
Data Loggers ◽  
Using Data ◽  
Species Specific

Abstract Physical dormancy (PY) is typically induced by seed coat impermeability that develops once the moisture content of seeds drops below a species-specific threshold. Considering this, we utilized Albizia julibrissin (Fabaceae) to ask (i) whether seeds that mature on the outer branches of trees (directly exposed to sunlight) are more likely to be impermeable than seeds matured under canopy cover; (ii) whether this difference might be explained by the maternal environment in which the seeds mature; and (iii) which conditions impose secondary dormancy following dispersal? Temperature was tracked in both shaded and sun-exposed seed pods throughout the growing season using data-loggers. Temperatures remained lower in pods under canopy cover than those exposed to direct sunlight. Consequently, the moisture content of seeds collected from sun-exposed branches were significantly lower than seeds matured under canopy cover, thereby producing a higher percentage of impermeable seeds. A dispersal-mimicking experiment revealed that seeds matured in sun-exposed branches and subsequently dispersed to an open site for 4 months were more likely to develop impermeability (i.e. secondary dormancy). The opposite was found to be true for seeds matured in shaded branches and subsequently dispersed to a canopy-covered site. We conclude that the microclimate of both the maternal environment in which seeds mature, and the site to which they disperse, determines the development of primary and secondary dormancy, respectively.

Total weak acid concentration and effective dissociation constant of nonvolatile buffers in human plasma

2001 ◽  
Vol 91 (3) ◽  
pp. 1364-1371 ◽  
Author(s):  
Peter D. Constable
Keyword(s):  
Dissociation Constant ◽  
Human Plasma ◽  
Total Concentration ◽  
Weak Acid ◽  
Strong Ion Difference ◽  
Acid Base ◽  
Horse Plasma ◽  
Using Data ◽  
Species Specific

The strong ion approach provides a quantitative physicochemical method for describing the mechanism for an acid-base disturbance. The approach requires species-specific values for the total concentration of plasma nonvolatile buffers (Atot) and the effective dissociation constant for plasma nonvolatile buffers ( K a), but these values have not been determined for human plasma. Accordingly, the purpose of this study was to calculate accurate Atot and K a values using data obtained from in vitro strong ion titration and CO2tonometry. The calculated values for Atot (24.1 mmol/l) and K a (1.05 × 10−7) were significantly ( P < 0.05) different from the experimentally determined values for horse plasma and differed from the empirically assumed values for human plasma (Atot = 19.0 meq/l and K a = 3.0 × 10−7). The derivatives of pH with respect to the three independent variables [strong ion difference (SID), Pco 2, and Atot] of the strong ion approach were calculated as follows: [Formula: see text] [Formula: see text], [Formula: see text]where S is solubility of CO2 in plasma. The derivatives provide a useful method for calculating the effect of independent changes in SID+, Pco 2, and Atot on plasma pH. The calculated values for Atot and K a should facilitate application of the strong ion approach to acid-base disturbances in humans.

Explaining variability in parasite aggregation levels among host samples

Parasitology ◽  
2013 ◽  
Vol 140 (4) ◽  
pp. 541-546 ◽  
Author(s):  
ROBERT POULIN
Keyword(s):  
Body Size ◽  
Strong Relationship ◽  
Host Susceptibility ◽  
Helminth Parasites ◽  
Susceptibility To Infection ◽  
Host Body ◽  
Parasite Aggregation ◽  
Using Data ◽  
Species Specific ◽  
Host Body Size

SUMMARYAggregated distributions among individual hosts are a defining feature of metazoan parasite populations. Heterogeneity among host individuals in exposure to parasites or in susceptibility to infection is thought to be the main factor generating aggregation, with properties of parasites themselves explaining some of the variability in aggregation levels observed among species. Here, using data from 410 samples of helminth parasites on fish hosts, I tested the contribution of (i) within-sample variation in host body size, taken as a proxy for variability in host susceptibility, and (ii) parasite taxon and developmental stage, to the aggregated distribution of parasites. Log-transformed variance in numbers of parasites per host was regressed against log mean number across all samples; the strong relationship (r2 = 0·88) indicated that aggregation levels are tightly constrained by mean infection levels, and that only a small proportion of the observed variability in parasite aggregation levels remains to be accounted for by other factors. Using the residuals of this regression as measures of ‘unexplained’ aggregation, a mixed effects model revealed no significant effect of within-sample variation in host body size or of parasite taxon or stage (i.e. juvenile versus adult) on parasite aggregation level within a sample. However, much of the remaining variability in parasite aggregation levels among samples was accounted for by the number of individual hosts examined per sample, and species-specific and study-specific effects reflecting idiosyncrasies of particular systems. This suggests that with most differences in aggregation among samples already explained, there may be little point in seeking universal causes for the remaining variation.

What's hot and what's not: defining torpor in free-ranging birds and mammals

2001 ◽  
Vol 79 (10) ◽  
pp. 1885-1890 ◽  
Author(s):  
Robert MR Barclay ◽  
Cori L Lausen ◽  
Lydia Hollis
Keyword(s):  
Body Temperature ◽  
The Body ◽  
Temperature Sensitive ◽  
The Past ◽  
Data Loggers ◽  
Temperature Thresholds ◽  
Radio Transmitters ◽  
Species Specific ◽  
Free Ranging ◽  
Lowered Body

With the development of small implantable data loggers and externally attached temperature-sensitive radio transmitters, increasing attention is being paid to determining the thermoregulatory strategies of free-ranging birds and mammals. One of the constraints of such studies is that without a direct measure of metabolic rate, it is difficult to determine the significance of lowered body temperatures. We surveyed the literature and found that many different definitions have been used to discriminate torpor from normothermy. Many studies use arbitrary temperature thresholds without regard for the normothermic body temperature of the individuals or species involved. This variation makes comparison among studies difficult and means that ecologically and energetically significant small reductions in body temperature may be overlooked. We suggest that normothermic body temperature for each individual animal should be determined and that torpor be defined as occurring when the body temperature drops below that level. When individuals' active temperatures are not available, a species-specific value should be used. Of greater value, however, are the depth and duration of torpor bouts. We suggest several advantages of this definition over those used in the past.

Seed development in Malva parviflora: onset of germinability, dormancy and desiccation tolerance

2007 ◽  
Vol 47 (6) ◽  
pp. 683 ◽  
Author(s):  
Pippa J. Michael ◽  
Kathryn J. Steadman ◽  
Julie A. Plummer
Keyword(s):  
Moisture Content ◽  
Seed Development ◽  
Desiccation Tolerance ◽  
Dry Weight ◽  
Physical Dormancy ◽  
Seed Moisture Content ◽  
Physiological Maturity ◽  
Seed Moisture ◽  
Physiological Dormancy ◽  
Malva Parviflora

Seed development was examined in Malva parviflora. The first flower opened 51 days after germination; flowers were tagged on the day that they opened and monitored for 33 days. Seeds were collected at 12 stages during this period and used to determine moisture content, germination of fresh seeds and desiccation tolerance (seeds dried to 10% moisture content followed by germination testing). Seed moisture content decreased as seeds developed, whereas fresh (max. 296 mg) and dry weight (max. 212 mg) increased to peak at 12–15 and ~21 days after flowering (DAF), respectively. Therefore, physiological maturity occurred at 21 DAF, when seed moisture content was 16–21%. Seeds were capable of germinating early in development, reaching a maximum of 63% at 9 DAF, but germination declined as development continued, presumably due to the imposition of physiological dormancy. Physical dormancy developed at or after physiological maturity, once seed moisture content declined below 20%. Seeds were able to tolerate desiccation from 18 DAF; desiccation hastened development of physical dormancy and improved germination. These results provide important information regarding M. parviflora seed development, which will ultimately improve weed control techniques aimed at preventing seed set and further additions to the seed bank.

scholarly journals Evaluating the Effects of Projected Climate Change on Forest Fuel Moisture Content

2014 ◽  
Vol 37 ◽  
pp. 65-69
Author(s):  
Kellen Nelson ◽  
Daniel Tinker
Keyword(s):  
Climate Change ◽  
Moisture Content ◽  
Stand Structure ◽  
Canopy Cover ◽  
Fire Season ◽  
Climate Change Scenarios ◽  
Fuel Moisture ◽  
Mature Forest ◽  
Forest Fuel ◽  
Fuel Moisture Content

Understanding how live and dead forest fuel moisture content (FMC) varies with seasonal weather and stand structure will improve researchers’ and forest managers’ ability to predict the cumulative effects of weather on fuel drying during the fire season and help identify acute conditions that foster wildfire ignition and high rates of fire spread. No studies have investigated the efficacy of predicting FMC using mechanistic water budget models at daily time scales through the fire season nor have they investigated how FMC may vary across space. This study addresses these gaps by (1) validating a novel mechanistic live FMC model and (2) applying this model with an existing dead FMC model at three forest sites using five climate change scenarios to characterize how FMC changes through time and across space. Sites include post-fire 24-year old forest, mature forest with high canopy cover, and mature forest affected by the mountain pine beetle with moderate canopy cover. Climate scenarios include central tendency, warm/dry, warm/wet, hot/dry, and hot/wet.

scholarly journals Playing by different rules: indicators of happiness on playgrounds

2021 ◽  
Author(s):  
Michelle Rowland
Keyword(s):  
Logistic Regression ◽  
Elementary Schools ◽  
Critical Role ◽  
Pilot Project ◽  
Outdoor Play ◽  
Social Health ◽  
Community Interest ◽  
Significant Relationships ◽  
Public Elementary Schools ◽  
Using Data

As our cities continue to urbanize, opportunities for children’s unstructured outdoor play are declining. Play is a right to children, and holds a critical role in children’s lives. Creating opportunities for play during school hours produces significant physical and social health benefits. OPAL (Outdoor Play and Learning) is a registered community interest program originating in England transforming attitudes to play supervision, environment and provision within schools. In Toronto, Canada an OPAL pilot project is being implemented at six public elementary schools. Using data from this pilot, this study examines how differences in happiness while playing at schools vary across play conditions and duration. The study explores baseline data collected in Spring 2016 among 352 of 9-12-year-old children, attending grades 4 to 6. Binomial logistic regression was performed for recess and lunch play showing the correlation between happiness and play duration. There are statistically significant relationships between happiness and play conditions. Key words: outdoor play, unstructured, happiness, children, Toronto

Standardizing Instructions for Ice and Cold Pack Use Can Mitigate Summer Temperatures on Two Commercially Available Outdoor Courier Lockboxes

2021 ◽  
Vol 156 (Supplement_1) ◽  
pp. S119-S120
Author(s):  
S A Hart ◽  
J R Wiencek
Keyword(s):  
Extreme Temperatures ◽  
Direct Sunlight ◽  
Data Loggers ◽  
Summer Temperatures ◽  
The Mean ◽  
Using Data ◽  
Cold Pack ◽  
The Impact ◽  
And Storage

Abstract Introduction/Objective Clinical and Laboratory Standards Institute document GP44 recommends samples avoid temperatures &gt;22°C during sample transport and storage. Outdoor courier lockboxes used in external sample transport can experience extreme temperatures (&gt;40°C) in the summer. Ice (frozen at -20°C) and cold (refrigerated at 4-8°C) packs can be used to reduce internal lockbox temperatures during hot summer days. Unfortunately, there are no universally accepted instructions to maintain internal lockbox temperatures during these conditions. Therefore, our goal was to elucidate the impact of placing ice and cold packs at two specific time points to mitigate external summer temperatures in two commercially available outdoor courier lockboxes used at our institution. Methods/Case Report Two pairs of uniquely manufactured courier lockboxes (steel vs. urethane polymer) were placed outside in direct sunlight in Nashville, Tennessee during the second week of June 2021. Ambient outdoor and lockbox temperatures were monitored using data loggers during a four-day cycle. Each type of lockbox design had a control with no ice or cold packs. These controls were then compared to each experimental, paired lockbox with four ice packs placed at 8am and replaced with four cold packs at 4pm. Results (if a Case Study enter NA) The mean ambient outdoor temperature over these four days was 27.7°C (range: 22.2-39.8°C). Temperatures within the steel and urethane polymer lockboxes without ice or cold packs was 28.3°C (range: 22.4-40.8°C) and 31.6°C (range: 23.8-41.0°C), respectively. The addition of four ice packs at 8am and replaced with four cold packs at 4pm reduced temperatures in the steel box to 24.3°C (range: 17.4-27.9°C) whereas in the urethane polymer box temperatures were reduced to 13.4°C (range: 6.6-18.1°C). Conclusion Temperatures inside outdoor lockboxes can increase in summer commonly above the outdoor ambient temperature. Standardizing instructions for ice and cold packs can reduce internal outdoor courier lockbox temperatures during summer months, especially in urethane polymer lockboxes.

360 Body Temperature of Hair Sheep Ewes During the Postpartum Period and Around the Time of Mating in an Accelerated Lambing System in the Tropics

2021 ◽  
Vol 99 (Supplement_3) ◽  
pp. 200-201
Author(s):  
Robert Godfrey ◽  
Sue A Lakos
Keyword(s):  
Body Temperature ◽  
Postpartum Period ◽  
Post Partum ◽  
Production Cycle ◽  
Hair Sheep ◽  
Data Loggers ◽  
Breed Difference ◽  
Humidity Index ◽  
Using Data ◽  
The Tropics

Abstract The study was conducted to evaluate body temperature of hair sheep ewes at various stages of the production cycle in an accelerated lambing system in the tropics. Multiparous St. Croix White (STX: n = 7) and Dorper x STX (DRPX; n = 7) ewes lambing in October and raising single lambs weaned at 120 d were used. Synchronized breeding began at 96 d postpartum. Vaginal temperature (VT) was measured at 10-min intervals for 96 h at 38 and 66 d post-partum (PP1, PP2) and at 2 days after mating (PM) using data loggers. Daily minimum, maximum and range of VT were determined for ewes within PP1, PP2 and PB. Data were analyzed using GLM procedures of SAS with breed, day and time (PP1, PP2, PM) in the model. Mean ambient temperature, temperature-humidity index and solar radiation at PP1, PP2 and PM were 24.8 °C, 25.2 °C, 23.8 °C, and 74.7, 74.9, 73.3, and 180 W/m2, 160 W/m2 and 155 W/m2, respectively. Minimum VT was lower (P &lt; 0.002) in STX than DRPX ewes at PP1, PP2 but not PM (38.27 ± 0.04 vs 38.44 ± 0.04 °C, 38.16 ± 0.04 vs 38.33 ± 0.04 °C, 38.47 ± 0.04 vs 38.58 ± 0.04 °C, respectively). There was no difference in maximum VT between breed or time (P &gt; 01.0). There was no breed difference (P &gt; 0.10) in range of VT, but the range of VT was lower (P &lt; 0.0001) at PM compared to PP1 and PP2 (1.22 ± 0.04 vs 1.77 ± 0.04 vs 1.63 ± 0.04 °C, respectively). These results show that tropically adapted STX ewes have lower body temperatures, as shown by the lower minimal VT which indicates a degree of nighttime cooling, during the postpartum period compared to DRPX ewes in a tropical environment.

Sexual Selection, Timing and an X–Y Homologous Gene: Did Homo Sapiens Speciate on the Y Chromosome?

2004 ◽  
Author(s):  
Tim J. Crow
Keyword(s):  
Sexual Selection ◽  
Sex Chromosome ◽  
Homo Sapiens ◽  
Single Gene ◽  
Critical Role ◽  
Hominid Evolution ◽  
Homologous Gene ◽  
Chromosomal Change ◽  
Species Specific ◽  
Sex Chromosome Aneuploidies

This chapter provides a theory of the speciation of modern Homo sapiens, that a single gene played a critical role in the transition from a precursor species. The theory is founded upon the following: firstly, the premise that hemispheric asymmetry is the defining feature of the human brain and the only plausible correlate of language; secondly, an argument for a specific candidate region (the Xq21.3/Yp11.2 region of homology) based upon the reciprocal deficits associated with the sex chromosome aneuploidies, and the course of chromosomal change in hominid evolution; and thirdly, a particular evolutionary mechanism (sexual selection acting on an X-Y-linked gene) to account for species-specific modification of what initially was a saltational change. These postulates relate to the case of modern Homo sapiens. On the basis of the recent literature, the discussion argues that the third premise has general significance as a mechanism of speciation.

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