scholarly journals The Symptoms of Herbicidal Action: The Case of Aclonifen

2015 ◽  
Vol 3 (6) ◽  
pp. 472
Author(s):  
Özgür Kıvılcım Kılınç
Keyword(s):  
Plant Species ◽  
Mode Of Action ◽  
Treatment Effectiveness ◽  
Climatic Factors ◽  
Field Conditions ◽  
Field Scale ◽  
Modes Of Action ◽  
Indirect Consequence ◽  
Accurate Observation ◽  
Current Report

The symptoms which were directly bound to the biochemical mode of action of an herbicide, other symptoms result from an indirect consequence of this action. The symptoms of herbicidal action deeply differed and that the climatic factors during the two first weeks after treatment could change definitely the result of the selective herbicide action. The repetitive observation of symptoms allows to inform the farmer about the tolerance or resistance of certain plant species, including the culture, for instance through the appearance of symptoms on the first leaves of the seedlings and their absence in the following leaves. As a whole, the accurate observation of herbicidal symptoms on plants is the essential, rapid and non-expensive analysis of treatment effectiveness at the field scale. The purpose of the current report is to describe the symptoms of a very complex herbicidal action, that of aclonifen involving two modes of action for the same molecule, approximately at the same concentration, and to compare these symptoms under field conditions and under controlled conditions, for a better understanding.

scholarly journals Altitudinally coordinated pattern of plant community structure in the Shivapuri National Park, Nepal

1970 ◽  
Vol 18 (1) ◽  
pp. 11-17 ◽  
Author(s):  
Shalik Ram Sigdel
Keyword(s):  
Community Structure ◽  
Species Diversity ◽  
Plant Species ◽  
Plant Community ◽  
National Park ◽  
Climatic Factors ◽  
Flower Colour ◽  
Basal Area ◽  
Plant Community Structure ◽  
Closed Canopy

Study on plant community structure was undertaken in different altitudinal ranges of Shivapuri National Park. The general objective of this study is to analyse different plant community structure in Shivapuri National Park with regards to altitudinal variation. The forest was divided into three distinct altitudinal ranges on the basis of dominancy. In each altitudinal range standard quadrats method was applied for vegetation analysis. The highest number of species was found in site II. All the ecological parameters of the plant species were higher in site II except Basal Area of tree that was highest in site III. The pattern of distribution of plant species was not uniform according to altitude. At higher elevation, the forest was mature with almost closed canopy and trees were large; so the tree density was low. Species richness was highest in site II. Species diversity among tree and shrub species was higher in site I. But for herb species diversity was higher in site II for both seasons. Such type of variations may be due to nature of soil i.e. acidity, nutrient availability and other micro-climatic factors. The most noteworthy thing was that variation in flower colour of Rhododendron arboreum i.e. deep scarlet at low altitude, but it gradually changed into pinkish white as altitude increased. Key words: Altitude, Density, Plant community, Species diversity doi: 10.3126/banko.v18i1.2161 Banko Janakari, Vol. 18, No. 1, 11-17

Chemical Approaches for Improving Herbicide Selectivity and Crop Tolerance

Weed Science ◽  
1987 ◽  
Vol 35 (S1) ◽  
pp. 24-27 ◽  
Author(s):  
G. R. Stephenson ◽  
G. Ezra
Keyword(s):  
Weed Control ◽  
Plant Species ◽  
Mode Of Action ◽  
Crop Plants ◽  
Control Efficacy ◽  
New Approach ◽  
Crop Tolerance ◽  
Important Crop ◽  
Herbicide Metabolism ◽  
Equal Efficacy

Combinations of antagonistic herbicides can be helpful in the search for seed-applied chemical safeners to protect crop plants from herbicide injury. If a particular herbicide combination is selectively antagonistic so that the crop is not injured but weed control efficacy is not reduced, it should be possible to develop a new, more selective formulation of the herbicide which includes the antagonist or antidote. A promising new approach involves the use of early pretreatments of crop plants with subtoxic levels of a particular herbicide to increase crop tolerance to later, higher rates of that herbicide. When there are different mechanisms for herbicide detoxification in different plant species, it should also be possible to develop selective herbicide synergists that would provide equal efficacy at lower rates with greater crop tolerance. As our knowledge of herbicide metabolism and mode of action develops, it will be increasingly possible to use other chemicals to selectively synergize or safen herbicides to solve problems in important crop-weed situations.

scholarly journals Epidemiological studies of Fasciola gigantica infections in cattle in the highveld and lowveld communal grazing areas of Zimbabwe

2006 ◽  
Vol 73 (1) ◽  
Author(s):  
D.M. Pfukenyi ◽  
Pfukenyi Mukaratirwa ◽  
A.L. Willingham ◽  
J. Monrad
Keyword(s):  
Intermediate Host ◽  
Plant Species ◽  
Aquatic Vegetation ◽  
Climatic Factors ◽  
Fasciola Gigantica ◽  
Snail Species ◽  
Snail Population ◽  
Adult Cattle ◽  
Host Snail ◽  
Faecal Samples

During the period between January 1999 and December 2000, the distribution and seasonal patterns of Fasciola gigantica infections in cattle in the highveld and lowveld communal grazing areas of Zimbabwe were determined through monthly coprological examination. Cattle faecal samples were collected from 12 and nine dipping sites in the highveld and lowveld communal grazing areas respectively. Patterns of distribution and seasonal fluctuations of the intermediate host-snail populations and the climatic factors influencing the distribution were also determined by sampling at monthly intervals for a period of 24 months (November 1998 to October 2000) in six dams and six streams in the highveld and in nine dams in the lowveld communal grazing areas. Each site was sampled for relative snail density and the vegetation cover and type, physical and chemical properties of water, and mean monthly rainfall and temperature were recorded. Aquatic vegetation and grass samples 0-1 m from the edges of the snail habitats were collected monthly to determine the presence or absence of F. gigantica metacercariae. Snails collected at the same time were individually checked for the emergence of larval stages of F. gigantica. A total of 16 264 (calves 5 418; weaners 5 461 and adults 5 385) faecal samples were collected during the entire period of the study and 2 500 (15.4 %) of the samples were positive for F. gigantica eggs. Significantly higher prevalences were found in the highveld compared to the lowveld (P < 0.001), for adult cattle than calves ( P < 0.01) and in the wet season over the dry season (P < 0.01). Faecal egg output peaked from August / September to March / April for both years of the study. Lymnaea natalensis, the snail intermediate host of F. gigantica was recorded from the study sites with the highveld having a significantly higher abundance of the snail species than the lowveld (P < 0.01). The snail population was low between December and March and started to increase in April reaching a peak in September / October. The number of juvenile snails peaked between April and August. The mean number of snails collected was negatively correlated with rainfall and positively correlated with temperature. Mean number of snails collected was also positively correlated with Potamogeton plant species and negatively correlated with Cyperus plant species. However, none of the L. natalensis collected from the habitats were found shedding Fasciola cercariae. Metacercariae were found on herbage from the fringes of the snail habitats between February and August for both years, with most of the metacercariae concentrated on herbage 0-1 m from the banks of the habitats. Based on the findings of this study, anthelmintic treatment should be administered in December / January to control chronic and mature fasciolosis. A second treatment should be given in April / May to reduce pasture contamination and subsequently snail infection, as this is the time the snail population starts to build up. To control acute fasciolosis due to the immature liver flukes a third treatment should be given in August. The first application of molluscicides to control the snail intermediate hosts can be done in June the time when the snail is harbouring the parasite and a second application in September in order to kill new generations of infected snails.

scholarly journals The use of valinomycin, nigericin and trichlorocarbanilide in control of the protonmotive force in Escherichia coli cells

1983 ◽  
Vol 212 (1) ◽  
pp. 105-112 ◽  
Author(s):  
S Ahmed ◽  
I R Booth
Keyword(s):  
Escherichia Coli ◽  
Membrane Potential ◽  
Mode Of Action ◽  
Ph Gradient ◽  
Protonmotive Force ◽  
Modes Of Action ◽  
Escherichia Coli Cells ◽  
Low Concentrations ◽  
High K ◽  
Specific Control

Valinomycin, nigericin and trichlorocarbanilide were assessed for their ability to control the protonmotive force in Escherichia coli cells. Valinomycin, at high K+ concentrations, was found to decrease the membrane potential delta phi and indirectly to decrease the pH gradient delta pH. Nigericin was found to have two modes of action. At low concentrations (0.05-2 microM) it carried out K+/H+ exchange and decreased delta pH. At higher concentrations (50 microM) it carried out a K+-dependent transfer of H+, decreasing both delta phi and delta pH. In EDTA-treated cells only the latter mode of action was evident, whereas in a mutant sensitive to deoxycholate both types of effect were observed. Trichlorocarbanilide is proposed as an alternative to nigericin for the specific control of delta pH, and it can be used in cells not treated with EDTA.

Pharmacology of TMS measures

2012 ◽  
Author(s):  
Ulf Ziemann
Keyword(s):  
Motor Cortex ◽  
Mode Of Action ◽  
Cortical Excitability ◽  
Drug Effects ◽  
Main Mode ◽  
Multiple Modes ◽  
Modes Of Action ◽  
Health And Disease ◽  
Cortical Physiology ◽  
Chronic Drug Effects

This article discusses various aspects of the pharmacology of transcranial magnetic stimulator (TMS) measures. TMS measures reflect axonal, or excitatory or inhibitory synaptic excitability in distinct interneuron circuits. TMS measures can be employed to study the effects of a drug with unknown or multiple modes of action, and hence to determine its main mode of action at the systems level of the motor cortex. TMS experiments can also study acute drug effects that may be different from chronic drug effects. TMS or repetitive TMS may induce changes in endogenous neurotransmitter or neuromodulator systems. This allows for the study of neurotransmission along defined neuronal projections in health and disease. This article describes pharmacological experiments that have characterized the physiology of TMS measures of motor cortical excitability. Pharmacological challenging of TMS measures has opened a broad window into human cortical physiology.

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