Acid phosphatase activity of intact roots and phosphorus nutrition in plants. 1. Assay conditions and phosphatase activity

1980 ◽  
Vol 31 (3) ◽  
pp. 429 ◽  
Author(s):  
KD McLachlan
Keyword(s):  
Reaction Time ◽  
Phosphatase Activity ◽  
Microbial Contamination ◽  
Plant Root ◽  
Phosphorus Deficiency ◽  
Reaction Times ◽  
Subterranean Clover ◽  
Phosphorus Nutrition ◽  
Nitrophenyl Phosphate ◽  
Low Phosphorus

This veries sets out to investigate the possibility of developing root phosphatase activity as an indicator of plant efficiency in obtaining phosphorus from low phosphorus situations. This paper examines the effect of substrate pH, temperature, reaction time, microbial contamination and phosphorus nutrition on the expression of phosphatase activity of plant roots. Rye, wheat, buckwheat and subterranean clover plants have been used. Phosphatase (E.C. 3.1.3.4.1) activity measured by p-nitrophenyl phosphate (PNPP) assay was essentially the activity of the plant root. Increased acidity in the substrate, on its own, did not hydrolyse PNPP nor did microbial contamination significantly affect the plant value. Temperature and reaction time were positively related to the assay value, least variation in assay values occurring with substrate temperatures of 20�C and reaction times of 60-120 min. Optimum pH for phosphatase activity lay in the range pH 5-6. Deficient plants had greater activities than sufficient ones. There was no evidence of alkaline phosphatase activity with phosphorus deficiency. In wheat, the phosphatase activity increased within the first 4 days of plants being deprived of phosphorus and reached its peak in 8 days. Some of the phosphatase was soluble, but most was associated with the root itself. There was evidence that it could be strongly adsorbed on cellulose nitrate filters.

Effect of Phosphorus Deficiency on Phosphatase Activity of Cell Walls from Roots of Subterranean Clover

1984 ◽  
Vol 35 (4) ◽  
pp. 466-480 ◽  
Author(s):  
M. N. H. DRACUP ◽  
E. G. BARRETT-LENNARD ◽  
H. GREENWAY ◽  
A. D. ROBSON
Keyword(s):  
Phosphatase Activity ◽  
Cell Walls ◽  
Phosphorus Deficiency ◽  
Subterranean Clover

The role of vesicular-arbuscular mycorrhizas (VAM) in the phosphorus nutrition of cowpea (Vigna unguiculata (L.) Walp)

1991 ◽  
Vol 42 (1) ◽  
pp. 129 ◽  
Author(s):  
BM Ikombo ◽  
DG Edwards ◽  
CJ Asher
Keyword(s):  
Vigna Unguiculata ◽  
Phosphorus Deficiency ◽  
Phosphorus Nutrition ◽  
Strong Increase ◽  
Phosphorus Concentration ◽  
Sequence Of Events ◽  
Mycorrhizal Association ◽  
Low Phosphorus ◽  
Unsterilized Soil

An experiment was conducted to establish the role of VAM in the phosphorus nutrition and early growth of cowpea (Vigna unguiculata (L.) Walp.) cv. Vita 4 in a podzolic soil (Haplustult). The experiment involved four treatments: (1) plants grown in unsterilized soil adequately supplied with phosphorus (240 kg P ha-1), (2) plants grown in unsterilized soil with low phosphorus (10 kg P ha-1), (3) and (4) plants grown in methyl bromide sterilized soil with low phosphorus (10 kg P ha-1). Plants in treatments (1), (2) and (3) were inoculated with Bradyrhizobium. A series of harvests was taken from 14 to 42 days after sowing; 15 harvests at two-day intervals from treatment (2) and 5 harvests at 7-day intervals from the other treatments. Root infection by VAM did not occur in plants grown in the sterilized soil treatments (3) and (4); growth of these plants was poor, and they showed symptoms of severe phosphorus deficiency. Phosphorus concentrations in the youngest fully expanded leaf (YFEL) of plants grown in treatments (3) and (4) were in the range 0.10 to 0.16% at all harvests. Plants which were grown in the unsterilized soil with 240 kg P ha-l (treatment (1)) grew very well; they had a high concentration of phosphorus (0.3 1 to 0.75%) in the YFEL at all harvests and exhibited a delayed and reduced level of infection by VAM. Plants grown in the unsterilized soil with 10 kg P ha-l (treatment (2)) were strongly colonized by VAM; infection was apparent at 14 days after sowing and reached a maximum (85% of root segments colonized) at 36 days after sowing. A strong increase in phosphorus concentration in the YFEL of plants grown in treatment (2) commenced at 22 days after sowing, while an increase in dry matter yield and phosphorus content of the whole tops above that of non-mycorrhizal plants grown in the sterilized soil was observed at 30 days after sowing. The sequence of events leads us to conclude that the recovery of cowpea plants from early phosphorus deficiency stress resulted from increased phosphorus absorption following the development of a mycorrhizal association with the roots.

Modeling Within-Person Variance in Reaction Time Data of Older Adults

GeroPsych ◽  
2011 ◽  
Vol 24 (4) ◽  
pp. 169-176 ◽  
Author(s):  
Philippe Rast ◽  
Daniel Zimprich
Keyword(s):  
Reaction Time ◽  
Cognitive Aging ◽  
Reaction Times ◽  
Reaction Time Task ◽  
Reaction Time Data ◽  
Scale Model ◽  
Time Data ◽  
Time Task ◽  
The Mean ◽  
Second Wave

In order to model within-person (WP) variance in a reaction time task, we applied a mixed location scale model using 335 participants from the second wave of the Zurich Longitudinal Study on Cognitive Aging. The age of the respondents and the performance in another reaction time task were used to explain individual differences in the WP variance. To account for larger variances due to slower reaction times, we also used the average of the predicted individual reaction time (RT) as a predictor for the WP variability. Here, the WP variability was a function of the mean. At the same time, older participants were more variable and those with better performance in another RT task were more consistent in their responses.

The Level of Reaction Time Determines the ERP Correlates of Auditory Negative Priming

2006 ◽  
Vol 20 (3) ◽  
pp. 186-194 ◽  
Author(s):  
Susanne Mayr ◽  
Michael Niedeggen ◽  
Axel Buchner ◽  
Guido Orgs
Keyword(s):  
Reaction Time ◽  
Negative Priming ◽  
Effect Size ◽  
Priming Effect ◽  
Reaction Times ◽  
Negative Priming Effect ◽  
Episodic Retrieval ◽  
Time Level ◽  
Fast Reactions ◽  
Priming Condition

Responding to a stimulus that had to be ignored previously is usually slowed-down (negative priming effect). This study investigates the reaction time and ERP effects of the negative priming phenomenon in the auditory domain. Thirty participants had to categorize sounds as musical instruments or animal voices. Reaction times were slowed-down in the negative priming condition relative to two control conditions. This effect was stronger for slow reactions (above intraindividual median) than for fast reactions (below intraindividual median). ERP analysis revealed a parietally located negativity of the negative priming condition compared to the control conditions between 550-730 ms poststimulus. This replicates the findings of Mayr, Niedeggen, Buchner, and Pietrowsky (2003) . The ERP correlate was more pronounced for slow trials (above intraindividual median) than for fast trials (below intraindividual median). The dependency of the negative priming effect size on the reaction time level found in the reaction time analysis as well as in the ERP analysis is consistent with both the inhibition as well as the episodic retrieval account of negative priming. A methodological artifact explanation of this effect-size dependency is discussed and discarded.

The Effect of Retest Practice on the Speed-Ability Relationship

2004 ◽  
Vol 9 (1) ◽  
pp. 24-31 ◽  
Author(s):  
Sybille Rockstroh ◽  
Karl Schweizer
Keyword(s):  
Reaction Time ◽  
Skill Acquisition ◽  
Reaction Times ◽  
Cognitive Tasks ◽  
General Intelligence ◽  
Attention Switching ◽  
Letter Comparison ◽  
Sternberg Paradigm ◽  
The Relationship ◽  
Elementary Cognitive Tasks

Effects of four retest-practice sessions separated by 2 h intervals on the relationship between general intelligence and four reaction time tasks (two memory tests: Sternberg's memory scanning, Posner's letter comparison; and two attention tests: continuous attention, attention switching) were examined in a sample of 83 male participants. Reaction times on all tasks were shortened significantly. The effects were most pronounced with respect to the Posner paradigm and smallest with respect to the Sternberg paradigm. The relationship to general intelligence changed after practice for two reaction time tasks. It increased to significance for continuous attention and decreased for the Posner paradigm. These results indicate that the relationship between psychometric intelligence and elementary cognitive tasks depends on the ability of skill acquisition. In the search for the cognitive roots of intelligence the concept of learning seems to be of importance.

How Useful is the Power Law of Practice for Recognizing Practice in Concentration Tests?

2007 ◽  
Vol 23 (3) ◽  
pp. 157-165 ◽  
Author(s):  
Carmen Hagemeister
Keyword(s):  
Logistic Regression ◽  
Reaction Time ◽  
Power Law ◽  
Error Rate ◽  
Reaction Times ◽  
Practice Effect ◽  
Practice Effects ◽  
Rate Decrease ◽  
Small Practice

Abstract. When concentration tests are completed repeatedly, reaction time and error rate decrease considerably, but the underlying ability does not improve. In order to overcome this validity problem this study aimed to test if the practice effect between tests and within tests can be useful in determining whether persons have already completed this test. The power law of practice postulates that practice effects are greater in unpracticed than in practiced persons. Two experiments were carried out in which the participants completed the same tests at the beginning and at the end of two test sessions set about 3 days apart. In both experiments, the logistic regression could indeed classify persons according to previous practice through the practice effect between the tests at the beginning and at the end of the session, and, less well but still significantly, through the practice effect within the first test of the session. Further analyses showed that the practice effects correlated more highly with the initial performance than was to be expected for mathematical reasons; typically persons with long reaction times have larger practice effects. Thus, small practice effects alone do not allow one to conclude that a person has worked on the test before.

Porous Gel Coatings Obtained by Phase Separation in ORMOSIL System

2000 ◽  
Vol 628 ◽  
Author(s):  
Kazuki Nakanishi ◽  
Souichi Kumon ◽  
Kazuyuki Hirao ◽  
Hiroshi Jinnai
Keyword(s):  
Phase Separation ◽  
Reaction Time ◽  
Volume Fraction ◽  
Sol Gel ◽  
Reaction Times ◽  
Dip Coating ◽  
Coating Solution ◽  
Coating Method ◽  
Gel Phase ◽  
Dip Coating Method

ABSTRACTMacroporous silicate thick films were prepared by a sol-gel dip-coating method accompanied by the phase separation using methyl-trimethoxysilane (MTMS), nitric acid and dimethylformamide (DMF) as starting components. The morphology of the film varied to a large extent depending on the time elapsed after the hydrolysis until the dipping of the coating solution. On a glass substrate, the films prepared by early dipping had inhomogeneous submicrometer-sized pores on the surface of the film. At increased reaction times, relatively narrow sized isolated macropores were observed and their size gradually decreased with the increase of reaction time. On a polyester substrate, in contrast, micrometer-sized isolated spherical gel domains were homogeneously deposited by earlier dippings. With an increase of reaction time, the volume fraction of the gel phase increased, then the morphology of the coating transformed into co-continuous gel domains and macropores, and finally inverted into the continuous gel domains with isolated macropores. The overall morphological variation with the reaction time was explained in terms of the phase separation and the structure freezing by the forced gelation, both of which were induced by the evaporation of methanol during the dipping operation.

scholarly journals Manipulations of the Response-Stimulus Intervals as a Factor Inducing Controlled Amount of Reaction Time Intra-Individual Variability

2021 ◽  
Vol 11 (5) ◽  
pp. 669
Author(s):  
Paweł Krukow ◽  
Małgorzata Plechawska-Wójcik ◽  
Arkadiusz Podkowiński
Keyword(s):  
Reaction Time ◽  
Simple Reaction Time ◽  
Reaction Times ◽  
Reaction Time Task ◽  
Assessment Method ◽  
Individual Variability ◽  
Simple Reaction Time Task ◽  
Stimulus Interval ◽  
Simple Reaction ◽  
Response Stimulus

Aggrandized fluctuations in the series of reaction times (RTs) are a very sensitive marker of neurocognitive disorders present in neuropsychiatric populations, pathological ageing and in patients with acquired brain injury. Even though it was documented that processing inconsistency founds a background of higher-order cognitive functions disturbances, there is a vast heterogeneity regarding types of task used to compute RT-related variability, which impedes determining the relationship between elementary and more complex cognitive processes. Considering the above, our goal was to develop a relatively new assessment method based on a simple reaction time paradigm, conducive to eliciting a controlled range of intra-individual variability. It was hypothesized that performance variability might be induced by manipulation of response-stimulus interval’s length and regularity. In order to verify this hypothesis, a group of 107 healthy students was tested using a series of digitalized tasks and their results were analyzed using parametric and ex-Gaussian statistics of RTs distributional markers. In general, these analyses proved that intra-individual variability might be evoked by a given type of response-stimulus interval manipulation even when it is applied to the simple reaction time task. Collected outcomes were discussed with reference to neuroscientific concepts of attentional resources and functional neural networks.

scholarly journals Indicators of Targeted Physical Fitness in Judo and Jujutsu—Preliminary Results of Research

2021 ◽  
Vol 18 (8) ◽  
pp. 4347
Author(s):  
Wojciech J. Cynarski ◽  
Jan Słopecki ◽  
Bartosz Dziadek ◽  
Peter Böschen ◽  
Paweł Piepiora
Keyword(s):  
Reaction Time ◽  
Visual Stimulation ◽  
Intrinsic Value ◽  
Reaction Times ◽  
Arithmetic Means ◽  
Simple Reaction ◽  
Martial Art ◽  
Student’S T ◽  
Pearson Correlations ◽  
Student’S T Test

(1) Study aim: This is a comparative study for judo and jujutsu practitioners. It has an intrinsic value. The aim of this study was to showcase a comparison of practitioners of judo and a similar martial art jujutsu with regard to manual abilities. The study applied the measurement of simple reaction time in response to a visual stimulus and handgrip measurement. (2) Materials and Methods: The group comprising N = 69 black belts from Poland and Germany (including 30 from judo and 39 from jujutsu) applied two trials: “grasping of Ditrich rod” and dynamometric handgrip measurement. The analysis of the results involved the calculations of arithmetic means, standard deviations, and Pearson correlations. Analysis of the differences (Mann–Whitney U test) and Student’s t-test were also applied to establish statistical differences. (3) Results: In the test involving handgrip measurement, the subjects from Poland (both those practicing judo and jujutsu) gained better results compared to their German counterparts. In the test involving grasping of Ditrich rod, a positive correlation was demonstrated in the group of German judokas between the age and reaction time of the subjects (rxy = 0.66, p < 0.05), as well as in the group of jujutsu subjects between body weight and the reaction time (rxy = 0.49, p < 0.05). A significant and strong correlation between handgrip and weight was also established for the group of German judokas (rxy = 0.75, p < 0.05). In Polish competitors, the correlations were only established between the age and handgrip measurements (rxy = 0.49, p < 0.05). (4) Conclusions: Simple reaction times in response to visual stimulation were shorter in the subjects practicing the martial art jujutsu. However, the statement regarding the advantage of the judokas in terms of handgrip force was not confirmed by the results.

scholarly journals Lateralization of attention in adults with ADHD: Evidence of pseudoneglect

2020 ◽  
Vol 63 (1) ◽  
Author(s):  
Bartosz Helfer ◽  
Stefanos Maltezos ◽  
Elizabeth Liddle ◽  
Jonna Kuntsi ◽  
Philip Asherson
Keyword(s):  
Reaction Time ◽  
Visual Field ◽  
Reaction Times ◽  
Study Participant ◽  
Reaction Time Task ◽  
Right Visual Field ◽  
Time Variability ◽  
Incentive Condition ◽  
Reaction Time Variability ◽  
The Right

Abstract Background. We investigated whether adults with attention-deficit/hyperactivity disorder (ADHD) show pseudoneglect—preferential allocation of attention to the left visual field (LVF) and a resulting slowing of mean reaction times (MRTs) in the right visual field (RVF), characteristic of neurotypical (NT) individuals —and whether lateralization of attention is modulated by presentation speed and incentives. Method. Fast Task, a four-choice reaction-time task where stimuli were presented in LVF or RVF, was used to investigate differences in MRT and reaction time variability (RTV) in adults with ADHD (n = 43) and NT adults (n = 46) between a slow/no-incentive and fast/incentive condition. In the lateralization analyses, pseudoneglect was assessed based on MRT, which was calculated separately for the LVF and RVF for each condition and each study participant. Results. Adults with ADHD had overall slower MRT and increased RTV relative to NT. MRT and RTV improved under the fast/incentive condition. Both groups showed RVF-slowing with no between-group or between-conditions differences in RVF-slowing. Conclusion. Adults with ADHD exhibited pseudoneglect, a NT pattern of lateralization of attention, which was not attenuated by presentation speed and incentives.

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