Differential responses of growth, photosynthesis, respiration, and phosphate uptake to copper in copper-tolerant and copper-intolerant strains of Scenedesmus acutus (Chlorophyceae)

1995 ◽  
Vol 73 (8) ◽  
pp. 1295-1303 ◽  
Author(s):  
Czeslawa Nalewajko ◽  
Mary M. Olaveson
Keyword(s):  
Phosphate Uptake ◽  
Sufficient Conditions ◽  
Copper Toxicity ◽  
Differential Sensitivity ◽  
Short Term ◽  
Scenedesmus Acutus ◽  
Physiological Processes ◽  
Photosynthesis And Respiration ◽  
Copper Tolerant

We detected significant differences in copper toxicity to growth and several physiological processes (e.g., photosynthesis, respiration, and phosphate uptake) in three strains of Scenedesmus acutus f. alternans demonstrating differential sensitivity to copper. The copper-intolerant strain (designated X-72) and the two copper-tolerant strains (designated X-Cu and B-4) were tested in long-term (5-day) growth bioassays and short-term (< 24 h) physiological experiments under both nutrient-sufficient and nutrient-limited conditions. The three strains showed the same pattern of sensitivity to copper for growth and for all physiological processes examined: the copper-intolerant strain, X-72, showed the greatest sensitivity, followed by X-Cu. B-4 was most tolerant. Under nutrient-sufficient conditions, growth was more sensitive to copper than photosynthesis or respiration. Depression of the growth rate to 50% of control occurred at 25, 56, and 175 nmol Cu/106 cells in X-72, X-Cu, and B-4, respectively. Photosynthesis and respiration were inhibited in cultures that were preexposed to algistatic copper dosages for 20 h prior to testing. Both processes were equally inhibited in X-72 (to about 8.5% of controls) and in X-Cu (to about 32% of controls), but respiration was more inhibited than photosynthesis in B-4 (to 47.7 vs. 67.1% of control rates). L-buthionine-S,R-sulfoximine (BSO), a known inhibitor of phytochelatin synthesis, significantly reduced the tolerance of photosynthesis to copper in X-72 but not in X-Cu or B-4. Short-term responses among several physiological processes were also examined under phosphorus and nitrogen limitation. In P-limited cultures, phosphate uptake was depressed by 50% at 3 nmol Cu/106 cells in X-72, and at 5.8 nmol Cu/106 cells in X-Cu and B-4. In N-limited cultures, photosynthesis was more tolerant to copper than in nutrient-sufficient conditions in both X-72 and X-Cu but less tolerant in B-4. Key words: copper toxicity, growth, nutrient limitation, nitrogen, phosphate uptake, photosynthesis, respiration, Scenedesmus.

Thermal acclimation of respiration but not photosynthesis in Pinus radiata

2008 ◽  
Vol 35 (6) ◽  
pp. 448 ◽  
Author(s):  
Lai Fern Ow ◽  
David Whitehead ◽  
Adrian S. Walcroft ◽  
Matthew H. Turnbull
Keyword(s):  
Pinus Radiata ◽  
Growth Temperature ◽  
Dark Respiration ◽  
Temperature Acclimation ◽  
Short Term ◽  
Photosynthesis And Respiration ◽  
Term Response ◽  
N Status ◽  
Respiratory Responses

Pinus radiata L. were grown in climate-controlled cabinets under three night/day temperature treatments, and transferred between treatments to mimic changes in growth temperature. The objective was to determine the extent to which dark respiration and photosynthesis in pre-existing and new needles acclimate to changes in growth temperatures. We also assessed whether needle nitrogen influenced the potential for photosynthetic and respiratory acclimation, and further assessed if short-term (instantaneous, measured over a few hours) respiratory responses are accurate predictors of long-term (acclimated, achieved in days–weeks) responses of respiration to changing temperature. Results show that respiration displayed considerable potential for acclimation. Cold and warm transfers resulted in some acclimation of respiration in pre-existing needles, but full acclimation was displayed only in new needles formed at the new growth temperature. Short-term respiratory responses were poor predictors of the long-term response of respiration due to acclimation. There was no evidence that photosynthesis in pre-existing or new needles acclimated to changes in growth temperature. N status of leaves had little impact on the extent of acclimation. Collectively, our results indicate that there is little likelihood that respiration would be significantly stimulated in this species as night temperatures increase over the range of 10–20°C, but that inclusion of temperature acclimation of respiration would in fact lead to a shift in the balance between photosynthesis and respiration in favour of carbon uptake.

scholarly journals A Unified Approach for Predicting Long- and Short-Term Capability Indices with Dependence on Manufacturing Target Bias

2008 ◽  
Vol 2008 ◽  
pp. 1-10 ◽  
Author(s):  
Nikhil T. Satyala ◽  
R. J. Pieper
Keyword(s):  
Sufficient Conditions ◽  
Unified Approach ◽  
New Paradigm ◽  
Process Mean ◽  
Short Term ◽  
Capability Index ◽  
Capability Indices ◽  
Distributed Process ◽  
Specific Formulation

It is shown that the exact solution for the capability index (CPI) for Gaussian-distributed process with target bias can be expressed in terms of an unbiased CPI and a normalized target bias. The principal advantage of this specific formulation is that it facilitates evaluation of the degradation of the capability of the process due to bias between process mean and the process target. It is shown how this formalism, initially developed for the short-term process, is readily extended to long-term process for which the distribution is Gaussian. Readily isolated in the latter case are the two long-term CPI degrading effects, namely, process instability and target bias. Sufficient conditions to guarantee that long-term processes are distributed as Gaussian are discussed. Within the context of these assumed conditions, a new paradigm for a long-term locator ‘‘k’’ is proposed. For a three sigma process the results indicate that the exact CPI model is a less pessimistic predictor than both of the industry CPI models tested.

Seasonality of foliar respiration in two dominant plant species from the Arctic tundra: response to long-term warming and short-term temperature variability

2014 ◽  
Vol 41 (3) ◽  
pp. 287 ◽  
Author(s):  
Mary A. Heskel ◽  
Danielle Bitterman ◽  
Owen K. Atkin ◽  
Matthew H. Turnbull ◽  
Kevin L. Griffin
Keyword(s):  
Carbon Cycling ◽  
Leaf Gas Exchange ◽  
Nitrogen Concentration ◽  
Temperature Variability ◽  
The Arctic ◽  
Photosynthetic Parameters ◽  
Carbon Exchange ◽  
Short Term ◽  
Photosynthesis And Respiration

Direct measurements of foliar carbon exchange through the growing season in Arctic species are limited, despite the need for accurate estimates of photosynthesis and respiration to characterise carbon cycling in the tundra. We examined seasonal variation in foliar photosynthesis and respiration (measured at 20°C) in two field-grown tundra species, Betula nana L. and Eriophorum vaginatum L., under ambient and long-term warming (LTW) conditions (+5°C), and the relationship of these fluxes to intraseasonal temperature variability. Species and seasonal timing drove most of the variation in photosynthetic parameters (e.g. gross photosynthesis (Agross)), respiration in the dark (Rdark) and light (Rlight), and foliar nitrogen concentration. LTW did not consistently influence fluxes through the season but reduced respiration in both species. Alongside the flatter respiratory response to measurement temperature in LTW leaves, this provided evidence of thermal acclimation. The inhibition of respiration by light increased by ~40%, with Rlight : Rdark values of ~0.8 at leaf out decreasing to ~0.4 after 8 weeks. Though LTW had no effect on inhibition, the cross-taxa seasonal decline in Rlight : Rdark greatly reduced respiratory carbon loss. Values of Rlight : Agross decreased from ~0.3 in both species to ~0.15 (B. nana) and ~0.05 (E. vaginatum), driven by decreases in respiratory rates, as photosynthetic rates remained stable. The influence of short-term temperature variability did not exhibit predictive trends for leaf gas exchange at a common temperature. These results underscore the influence of temperature on foliar carbon cycling, and the importance of respiration in controlling seasonal carbon exchange.

scholarly journals Contrasting effects of long term versus short-term nitrogen addition on photosynthesis and respiration in the Arctic

Plant Ecology ◽  
2013 ◽  
Vol 214 (10) ◽  
pp. 1273-1286 ◽  
Author(s):  
Martine J. van de Weg ◽  
Gaius R. Shaver ◽  
Verity G. Salmon
Keyword(s):  
Nitrogen Addition ◽  
The Arctic ◽  
Short Term ◽  
Photosynthesis And Respiration

Annual changes in corticosterone and its response to handling, tagging and short-term captivity in Nyctibatrachus humayuni

2020 ◽  
pp. 118-125
Author(s):  
Amruta M. Joshi
Keyword(s):  
Breeding Season ◽  
Differential Sensitivity ◽  
Energy Reserves ◽  
Short Term ◽  
Coping With Stress ◽  
Physiological Processes ◽  
Corticosterone Metabolites ◽  
Species Specific ◽  
Effective Conservation ◽  
Growth And Reproduction

Glucocorticoids (GCs) are primarily involved in mobilising energy reserves to various physiological processes including reproduction. During situations of stress, GCs also help in coping with stress by diverting energy away from processes such as growth and reproduction. Hence, studying annual and seasonal changes in GCs of wild populations can help in understanding their role in stress management and reproduction. The quantification of GCs in wild animals involves capturing, handling and restraining, which could be stressful. Moreover, different species may exhibit differential sensitivity to different stressors. Hence, determining species-specific sensitivities and responses to different stressors may help in developing effective conservation measures. In this context, we studied the annual and seasonal variations in corticosterone metabolites of the Bombay night frog, Nyctibatrachus humayuni. In addition, the effects of handling, marking and short-term captivity (24 h) on corticosterone metabolite levels of N. humayuni were determined. Our results show that urinary corticosterone metabolites (UCM) varied significantly annually and between the sexes; in males, the levels were highest during the breeding season, whilst in females, the levels were highest just before the breeding season. Interestingly, UCM levels of both the sexes were not affected by tagging with visual implant elastomer (VIE), and by short-term captivity, suggesting that these manipulations were not stressful in terms of corticosterone responses.

Global stability of atmospheric oxygen

1993 ◽  
Vol 1 (3) ◽  
pp. 217-229
Author(s):  
Egbert K. Duursma ◽  
Michel P. R. M. Boisson
Keyword(s):  
Organic Matter ◽  
Atmospheric Oxygen ◽  
Living Organism ◽  
Optimum Level ◽  
Short Term ◽  
Fossil Carbon ◽  
Fossil Fuel Burning ◽  
Short Time ◽  
Photosynthesis And Respiration

The atmospheric oxygen reserve is so huge that, in the short term of hundreds or thousands of years, only minor changes can be expected due to fossil fuel burning and deforestation. Each oxygen molecule passes through a living organism, on average, only once in 9000 years. As a consequence, the fastest regulating system must take of the order of hundreds of years. Nevertheless, it is possible that the actual oxygen level is not necessarily at the optimum level for life, but is just an accidental one in the course of the earth's history. Tropical forests are not the ‘lungs’ of the earth in terms of hundreds of years, but only on a much longer time scale, likewise for all other vegetation which produce humus and the long-term fossil carbon. The driving force is related to the slight differences caused by external factors between photosynthesis and respiration, with subsequent organic matter deposition or consumption for short time regulation of hundreds of years; while, for periods of millions of years, the regulation depends on changes of weathering or burial of fossil sedimentary organic matter.

Conceptual short-term memory (CSTM) supports core claims of Christiansen and Chater

2016 ◽  
Vol 39 ◽  
Author(s):  
Mary C. Potter
Keyword(s):  
Working Memory ◽  
Rapid Serial Visual Presentation ◽  
Language Comprehension ◽  
Short Term Memory ◽  
Visual Presentation ◽  
Long Term Memory ◽  
Short Term ◽  
Term Memory ◽  
Use Of Knowledge

AbstractRapid serial visual presentation (RSVP) of words or pictured scenes provides evidence for a large-capacity conceptual short-term memory (CSTM) that momentarily provides rich associated material from long-term memory, permitting rapid chunking (Potter 1993; 2009; 2012). In perception of scenes as well as language comprehension, we make use of knowledge that briefly exceeds the supposed limits of working memory.

Ultrastructural investigations of MDL 19,660-induced effects on the canine platelet and megakaryocyte

1990 ◽  
Vol 48 (3) ◽  
pp. 374-375
Author(s):  
D.E. Loudy ◽  
J. Sprinkle-Cavallo ◽  
J.T. Yarrington ◽  
F.Y. Thompson ◽  
J.P. Gibson
Keyword(s):  
Antidepressant Drug ◽  
Beagle Dogs ◽  
Long Term Effects ◽  
Short Term ◽  
Platelet Counts ◽  
Toxicological Studies ◽  
Induced Aggregation ◽  
Internal Architecture

Previous short term toxicological studies of one to two weeks duration have demonstrated that MDL 19,660 (5-(4-chlorophenyl)-2,4-dihydro-2,4-dimethyl-3Hl, 2,4-triazole-3-thione), an antidepressant drug, causes a dose-related thrombocytopenia in dogs. Platelet counts started to decline after two days of dosing with 30 mg/kg/day and continued to decrease to their lowest levels by 5-7 days. The loss in platelets was primarily of the small discoid subpopulation. In vitro studies have also indicated that MDL 19,660: does not spontaneously aggregate canine platelets and has moderate antiaggregating properties by inhibiting ADP-induced aggregation. The objectives of the present investigation of MDL 19,660 were to evaluate ultrastructurally long term effects on platelet internal architecture and changes in subpopulations of platelets and megakaryocytes.Nine male and nine female beagle dogs were divided equally into three groups and were administered orally 0, 15, or 30 mg/kg/day of MDL 19,660 for three months. Compared to a control platelet range of 353,000- 452,000/μl, a doserelated thrombocytopenia reached a maximum severity of an average of 135,000/μl for the 15 mg/kg/day dogs after two weeks and 81,000/μl for the 30 mg/kg/day dogs after one week.

Comparison of Auditory, Language, Memory, and Attention Abilities in Children With and Without Listening Difficulties

2020 ◽  
Vol 29 (4) ◽  
pp. 710-727
Author(s):  
Beula M. Magimairaj ◽  
Naveen K. Nagaraj ◽  
Alexander V. Sergeev ◽  
Natalie J. Benafield
Keyword(s):  
Auditory Processing ◽  
Short Term Memory ◽  
Group Differences ◽  
Long Term Memory ◽  
Short Term ◽  
Significant Group ◽  
Term Memory ◽  
Memory And Attention ◽  
Speed And Accuracy

Objectives School-age children with and without parent-reported listening difficulties (LiD) were compared on auditory processing, language, memory, and attention abilities. The objective was to extend what is known so far in the literature about children with LiD by using multiple measures and selective novel measures across the above areas. Design Twenty-six children who were reported by their parents as having LiD and 26 age-matched typically developing children completed clinical tests of auditory processing and multiple measures of language, attention, and memory. All children had normal-range pure-tone hearing thresholds bilaterally. Group differences were examined. Results In addition to significantly poorer speech-perception-in-noise scores, children with LiD had reduced speed and accuracy of word retrieval from long-term memory, poorer short-term memory, sentence recall, and inferencing ability. Statistically significant group differences were of moderate effect size; however, standard test scores of children with LiD were not clinically poor. No statistically significant group differences were observed in attention, working memory capacity, vocabulary, and nonverbal IQ. Conclusions Mild signal-to-noise ratio loss, as reflected by the group mean of children with LiD, supported the children's functional listening problems. In addition, children's relative weakness in select areas of language performance, short-term memory, and long-term memory lexical retrieval speed and accuracy added to previous research on evidence-based areas that need to be evaluated in children with LiD who almost always have heterogenous profiles. Importantly, the functional difficulties faced by children with LiD in relation to their test results indicated, to some extent, that commonly used assessments may not be adequately capturing the children's listening challenges. Supplemental Material https://doi.org/10.23641/asha.12808607

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