scholarly journals North American temperate conifer ( Tsuga canadensis ) reveals a complex physiological response to climatic and anthropogenic stressors

2020 ◽  
Vol 228 (6) ◽  
pp. 1781-1795
Author(s):  
Shelly A. Rayback ◽  
Soumaya Belmecheri ◽  
Mary H. Gagen ◽  
Andrea Lini ◽  
Rachel Gregory ◽  
...  
Keyword(s):  
North American ◽  
Physiological Response ◽  
Tsuga Canadensis ◽  
Anthropogenic Stressors

scholarly journals Widespread inbreeding and unexpected geographic patterns of genetic variation in eastern hemlock (Tsuga canadensis), an imperiled North American conifer

2011 ◽  
Vol 13 (2) ◽  
pp. 475-498 ◽  
Author(s):  
Kevin M. Potter ◽  
Robert M. Jetton ◽  
William S. Dvorak ◽  
Valerie D. Hipkins ◽  
Rusty Rhea ◽  
...  
Keyword(s):  
Genetic Variation ◽  
North American ◽  
Tsuga Canadensis ◽  
Eastern Hemlock ◽  
Geographic Patterns

scholarly journals Effects of fungal seed pathogens under conspecific and heterospecific trees in a temperate forest

2007 ◽  
Vol 85 (10) ◽  
pp. 918-925 ◽  
Author(s):  
Peter M. Kotanen
Keyword(s):  
North American ◽  
Acer Saccharum ◽  
Temperate Forest ◽  
Sugar Maple ◽  
Soil Fungi ◽  
Tsuga Canadensis ◽  
Temperate Zone ◽  
Eastern Hemlock ◽  
Soil Environment ◽  
Direct Feedback

This study investigated the impacts of soil fungi on seeds of two eastern North American temperate-zone trees: Acer saccharum Marsh. (sugar maple) and Tsuga canadensis (L.) Carr (eastern hemlock). Seeds of each species were buried at locations dominated by either conspecifics or heterospecifics. Half were protected with fungicide, and the net consequences for survival and germination were assessed. Net effects of fungicide usually were positive, indicating that pathogens affected seeds more strongly than any potential mutualists. Losses of A. saccharum to fungi were modest, and almost identical in areas dominated by itself versus areas dominated by T. canadensis. In contrast, fungal impacts on T. canadensis were strongly habitat-dependent: losses to fungi were high in T. canadensis-dominated sites, but not in A. saccharum-dominated sites. This result is consistent with an accumulation of host-specific pathogens, either by a direct feedback between T. canadensis and its fungal enemies, or indirectly through modification of the soil environment. Even though these two trees share similar habitats, responses to fungicide indicate that their seeds are affected very differently by the soil environment.

Effects of Invasion by Tsuga Canadensis on a North American Forest Ecosystem

1992 ◽  
pp. 34-44 ◽  
Author(s):  
Margaret B. Davis ◽  
Shinya Sugita ◽  
Randolph R. Calcote ◽  
Lee Frelich
Keyword(s):  
Forest Ecosystem ◽  
North American ◽  
Tsuga Canadensis

Leader growth and the architecture of three North American hemlocks

1981 ◽  
Vol 59 (4) ◽  
pp. 476-480 ◽  
Author(s):  
David E. Hibbs
Keyword(s):  
North American ◽  
Apical Meristem ◽  
Growing Season ◽  
Tsuga Canadensis ◽  
Height Growth ◽  
Growth Patterns ◽  
Lateral Branch ◽  
Continuous Branch ◽  
Architectural Models ◽  
Rhythmic Growth

Height growth in hemlock (Tsuga canadensis (L.) Carr., T. heterophylla (Raf.) Sarg., T. mertensiana (Bong.) Carr.) is by rhythmic growth of a monopodial axis with continuous branch production throughout the growing season. Leader growth is plagiotropic and leader erection is a process lasting several years. Two types of events disrupt the basically monopodial nature of the axis. (1) Frequent (43%) apical meristem death shifts dominance to a nearby lateral branch in T. canadensis. (2) Weak apical control allows occasional shifts in dominance from the leader to a branch without meristem death (13 and 24% in T. heterophylla and T. canadensis, respectively, but none in T. mertensiana). These growth patterns contain elements of several tree architectural models but fit none well.

Preliminary Report of a Comparative Study of Seminiferous Tubular Epithelium from Rats Flown on Cosmos 1887 and SL3

1988 ◽  
Vol 46 ◽  
pp. 276-277
Author(s):  
Walter J. Sapp ◽  
D.E. Philpott ◽  
C.S. Williams ◽  
K. Kato ◽  
J. Stevenson ◽  
...  
Keyword(s):  
Space Flight ◽  
Physiological Response ◽  
Preliminary Report ◽  
Complete Recovery ◽  
Environmental Constraints ◽  
Tubular Epithelium ◽  
Testicular Weight ◽  
Testicular Morphology ◽  
Normal Offspring ◽  
Rats And Mice

Space flight, with its unique environmental constraints such as immobilization, decreased and increased pressures, and radiation, is known to affect testicular morphology and spermatogenesis. Selye, summarized the manifestations of physiological response to nonspecific stress and he pointed out that atrophy of the gonads always occurred. Reports of data collected from two dogs flown in space for 22 days (Cosmos 110) indicate that there was an increase of 30 to 70% atypical spermatozoa when compared to ground based controls. Seventy-five days after the flight the abnormalities had decreased to the high normal value of 30% and mating of these dogs after this period produced normal offspring, suggesting complete recovery. Effects of immobilization and increased gravity were investigated by spinning rats and mice at 2x g for 8-9 weeks. A decrease in testicular weight was noted in spun animals when compared to controls. Immobilization has been show to cause arrest of spermatogenesis in Macaca meminstrins.

Reduction of spermatogonia and testosterone in rat testes flown on space lab-3

1986 ◽  
Vol 44 ◽  
pp. 248-249
Author(s):  
Delbert E. Philpott ◽  
W. Sapp ◽  
C. Williams ◽  
T. Fast ◽  
J. Stevenson ◽  
...  
Keyword(s):  
Social Interaction ◽  
Social Status ◽  
Population Size ◽  
Physiological Response ◽  
Social Rank ◽  
Reproductive Function ◽  
Testicular Development ◽  
Organ Weights ◽  
Reproductive Maturation ◽  
Metabolic Activities

Space Lab 3 (SL-3) was flown on Shuttle Challenger providing an opportunity to measure the effect of spaceflight on rat testes. Cannon developed the idea that organisms react to unfavorable conditions with highly integrated metabolic activities. Selye summarized the manifestations of physiological response to nonspecific stress and he pointed out that atrophy of the gonads always occurred. Many papers have been published showing the effects of social interaction, crowding, peck order and confinement. Flickinger showed delayed testicular development in subordinate roosters influenced by group numbers, social rank and social status. Christian reported increasing population size in mice resulted in adrenal hypertrophy, inhibition of reproductive maturation and loss of reproductive function in adults. Sex organ weights also declined. Two male dogs were flown on Cosmos 110 for 22 days. Fedorova reported an increase of 30 to 70% atypical spermatozoa consisting of tail curling and/or the absence of a tail.

Infection control in North American dental schools

1989 ◽  
Vol 53 (9) ◽  
pp. 532-537 ◽  
Author(s):  
E Sampson ◽  
VB Dhuru
Keyword(s):  
Infection Control ◽  
North American ◽  
Dental Schools

Treatment planning instruction in North American dental schools, 1984-85

1985 ◽  
Vol 49 (10) ◽  
pp. 702-706
Author(s):  
S Kennon ◽  
TF Sleamaker ◽  
AG Farman
Keyword(s):  
Treatment Planning ◽  
North American ◽  
Dental Schools

Adaptation of the Connected Speech Test: Rerecording and Passage Equivalency

2020 ◽  
Vol 29 (2) ◽  
pp. 259-264 ◽  
Author(s):  
Hasan K. Saleh ◽  
Paula Folkeard ◽  
Ewan Macpherson ◽  
Susan Scollie
Keyword(s):  
Speech Perception ◽  
North American ◽  
First Language ◽  
Intraclass Correlation ◽  
Normal Hearing ◽  
Connected Speech ◽  
Internal Reliability ◽  
Speech Test ◽  
The Mean ◽  
Unit Standard

Purpose The original Connected Speech Test (CST; Cox et al., 1987) is a well-regarded and often utilized speech perception test. The aim of this study was to develop a new version of the CST using a neutral North American accent and to assess the use of this updated CST on participants with normal hearing. Method A female English speaker was recruited to read the original CST passages, which were recorded as the new CST stimuli. A study was designed to assess the newly recorded CST passages' equivalence and conduct normalization. The study included 19 Western University students (11 females and eight males) with normal hearing and with English as a first language. Results Raw scores for the 48 tested passages were converted to rationalized arcsine units, and average passage scores more than 1 rationalized arcsine unit standard deviation from the mean were excluded. The internal reliability of the 32 remaining passages was assessed, and the two-way random effects intraclass correlation was .944. Conclusion The aim of our study was to create new CST stimuli with a more general North American accent in order to minimize accent effects on the speech perception scores. The study resulted in 32 passages of equivalent difficulty for listeners with normal hearing.

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