An Empirical Model of Stomatal Conductance

An empirical model of stomatal conductance is presented. The predictions of conductance correlate with experimental determinations of the responses to several kinds of short-term and long-term perturbations, including irradiance, temperature, CO2 and O2 partial pressures, and leaf age and nitrogen nutrition. The model is not mechanistic and cannot account for the observed functioning of stomata independent of mesophyll. Nevertheless its success in predicting responses in intact leaves means that the mathematical expressions used must be analogous to those describing actual functioning.

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Stomatal conductance in Cucumis sativus upon short-term and long-term exposures to low temperatures

Russian Journal of Plant Physiology ◽

10.1134/s102144371205007x ◽

2012 ◽

Vol 59 (5) ◽

pp. 696-699 ◽

Cited By ~ 4

Author(s):

E. N. Ikkonen ◽

T. G. Shibaeva ◽

M. I. Sysoeva ◽

E. G. Sherudilo

Keyword(s):

Stomatal Conductance ◽

Cucumis Sativus ◽

Low Temperatures ◽

Short Term

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Effect of Elevated CO2 Concentration on Leaf Photosynthesis in Sanjiang-Deyeuxia angustifolia

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.726-731.305 ◽

2013 ◽

Vol 726-731 ◽

pp. 305-309

Author(s):

Ming Yi Xu ◽

Ao Xue Wang ◽

Hong Wei Ni

Keyword(s):

Stomatal Conductance ◽

Chlorophyll Content ◽

Photosynthetic Parameters ◽

Leaf Photosynthesis ◽

Short Term ◽

Deyeuxia Angustifolia ◽

Different Levels ◽

Concentration Condition ◽

Photosynthetic Ability

Deyeuxia angustifolia were grown under three different levels of CO2concentration conditions, 370μmol mol-1(ambient CO2), 550μmol mol-1(elevated CO2) and 700μmol mol-1(elevated CO2) respectively. We investigated the responses of photosynthesis and growth ofD.angustifoliaunder different CO2concentration conditions. Leaf photosynthesis and chlorophyll content were checked. The results showed that the values of net photosynthetic rate (Pn), stomatal conductance (Gs), intercellular CO2concentration (Ci), transpiration (E), chlorophyll content were influenced by the elevated CO2concentrations. The photosynthetic parameters changed in parallel with CO2enrichment. CO2enrichment in short term improved the photosynthetic ability of leaves, whereas the capacity was weakened under long-term elevated CO2concentration condition. The leaves ofD.angustifoliagrown under elevated CO2concentrations at the end of growth, had lower Pn, Gs, Ci, E and chlorophyll content than those grown and measuered under ambient CO2concentration. The results indicated thatD.angustifoliaappeared photosynthetic acclimation.

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Ozone Amplifies Water Loss from Mature Trees in the Short Term But Decreases It in the Long Term

Forests ◽

10.3390/f11010046 ◽

2019 ◽

Vol 11 (1) ◽

pp. 46

Author(s):

Elena Paoletti ◽

Nancy E. Grulke ◽

Rainer Matyssek

Keyword(s):

Steady State ◽

Stomatal Conductance ◽

Gas Exchange ◽

Water Loss ◽

Vapour Pressure Deficit ◽

Environmental Parameters ◽

Mechanistic Explanation ◽

Short Term ◽

Mature Trees

We measured whole-tree transpiration of mature Fagus sylvatica and Picea abies trees exposed to ambient and twice-ambient O3 regimes (1xO3 and 2xO3 free-air fumigation). After eight years, mean daily total transpiration did not vary with the O3 regime over the 31 days of our study, even though individual daily values increased with increasing daily O3 peaks in both species. Although the environmental parameters were similar at 1xO3 and 2xO3, the main factors affecting daily transpiration were vapour pressure deficit in 2xO3 spruce and O3 peaks in beech. For a mechanistic explanation, we measured O3-induced sluggish stomatal responses to variable light (sunflecks) by means of leaf-level gas exchange measurements only in the species where O3 was a significant factor for transpiration, i.e., beech. Stomata were always slower in closing than in opening. The 2xO3 stomata were slower in opening and mostly in closing than 1xO3 stomata, so that O3 uptake and water loss were amplified before a steady state was reached. Such delay in the stomatal reaction suggests caution when assessing stomatal conductance under O3 pollution, because recording gas exchange at the time photosynthesis reached an equilibrium resulted in a significant overestimation of stomatal conductance when stomata were closing (ab. 90% at 1xO3 and 250% at 2xO3). Sun and shade leaves showed similar sluggish responses, thus suggesting that sluggishness may occur within the entire crown. The fact that total transpiration was similar at 1xO3 and 2xO3, however, suggests that the higher water loss due to stomatal sluggishness was offset by lower steady-state stomatal conductance at 2xO3. In conclusion, O3 exposure amplified short-term water loss from mature beech trees by slowing stomatal dynamics, while decreased long-term water loss because of lower steady-state stomatal conductance. Over the short term of this experiment, the two responses offset each other and no effect on total transpiration was observed.

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Physiological effects of short- and long-term exposure to elevated carbon dioxide on a freshwater mussel, Fusconaia flava

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/cjfas-2016-0083 ◽

2016 ◽

Vol 73 (10) ◽

pp. 1538-1546 ◽

Cited By ~ 14

Author(s):

Kelly D. Hannan ◽

Jennifer D. Jeffrey ◽

Caleb T. Hasler ◽

Cory D. Suski

Keyword(s):

Carbon Dioxide ◽

Freshwater Mussels ◽

Physiological Responses ◽

Freshwater Mussel ◽

Elevated Carbon Dioxide ◽

Initial Increase ◽

Short Term ◽

Partial Pressures ◽

Short And Long Term

Zones of elevated carbon dioxide (CO2) have the potential to deter the movement of fishes. Should CO2 be used as a barrier, non-target organisms, such as freshwater mussels, have the potential to be impacted. In this study, the physiological responses of adult Fusconaia flava exposed to elevated partial pressures of CO2 (pCO2) over both short-term (6 h exposure with 6 h recovery) and long-term (4-, 8-, and 32-day exposure) periods were measured. A 6 h exposure to either ∼15 000 μatm (1 atm = 101.325 kPa) or ∼200 000 μatm caused an elevation in hemolymph Ca2+. Exposure to ∼200 000 μatm resulted in a decrease in hemolymph Cl−, and exposure to ∼15 000 μatm caused an increase in hemolymph Na+, whereas ∼200 000 μatm caused a decrease. Exposure to elevated pCO2 for long-term periods caused a decrease in hemolymph Mg2+ and an initial increase in hemolymph Ca2+. Body condition and hemolymph glucose were not significantly influenced by elevated pCO2 for both experiments. This study shows that elevated pCO2 had limited impacts on the physiological responses of adult freshwater mussels.

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

Behavioral and Brain Sciences ◽

10.1017/s0140525x15000928 ◽

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.

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

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100159412 ◽

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.

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

American Journal of Audiology ◽

10.1044/2020_aja-20-00018 ◽

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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