Effect of Temperature on Photoreductive Activity of Chloroplasts From Passionfruit Species of Different Chilling Sensitivity

1978 ◽  
Vol 5 (4) ◽  
pp. 443 ◽  
Author(s):  
C Critchley ◽  
RM Smillie ◽  
BD Patterson
Keyword(s):  
Heat Stability ◽  
The Other ◽  
Effect Of Temperature ◽  
Tropical Species ◽  
Clear Correlation ◽  
Hill Reaction ◽  
Resistant Species ◽  
Chilling Sensitivity ◽  
Cold Tolerant ◽  
The Hill

The Hill reaction activity of chloroplast membranes isolated from five Passiflora species of different chilling sensitivity was determined as a function of temperature over the range 0 - 40°C. Activity was measured by the photoreduction of ferricyanide in the presence of gramicidin D. In two lowland tropical and chilling-sensitive species, P. quadrangularis and P. edulis forma flavicarpa, the apparent Arrhenius activation energy (Ea) for ferricyanide photoreduction was more than doubled at temperatures below 16 and 10°C, respectively. This increase in Ea was also characteristic of more chilling- resistant species. P. cincinnata, which is intermediate in chilling sensitivity between the two lowland tropical and the other two species studied, showed an increase in Ea below 15°C. A hybrid of this species with P. edulis forma flavicarpa behaved similarly. In chloroplasts from P. edulis, a species relatively resistant to chilling temperatures, there was an increase in Ea below 16°C, like that shown by P. quadrangularis, as well as another increase below 4°C. P. caerulea, the most chilling-resistant of the species studied, showed changes in Ea at 7 and 19°C. Thus, there was no clear correlation between the chilling sensitivity or resistance of a species and the presence or absence of a change in the temperature dependence of the Hill activity at low temperatures. The heat stability of the photoreductive activity of chloroplasts isolated from the various Passiflora species also did not correlate with their chilling sensitivity. The heat stability of photoreductive activity in the most cold-tolerant species, P. caerulea, was comparable with that found for the tropical species, while chloroplasts from P. cincinnata were more heat-labile than chloroplasts from the other species.

scholarly journals Galactolipase and chilling sensitivity of plants.

1997 ◽  
Vol 44 (1) ◽  
pp. 21-35 ◽  
Author(s):  
Z Kaniuga
Keyword(s):  
Fatty Acids ◽  
Membrane Lipids ◽  
Ph Dependence ◽  
Hill Reaction ◽  
High Melting Point ◽  
Lipid Acyl Hydrolase ◽  
Chilling Sensitivity ◽  
Acyl Lipids ◽  
The Hill

Galactolipase is a lipid acyl hydrolase (EC 3.1.1.26) acting predominantly on galactolipids which constitute up to 80% of total acyl lipids in chloroplast membrane. Evidence is presented on the involvement of this enzyme in plant response to chilling via degradation of membrane lipids and the increase of free fatty acids, associated with reduced oxygen evolution in the Hill reaction. The occurrence of two pools of fatty acids has been hypothesized. Analysis of numerous plant species showed higher galactolipase activity in the chilling-sensitive than in the chilling-resistant plants. Differences in the pH-dependence curve and in the response to detergents of galactolipases from these two groups of plants suggest heterogeneity of the enzyme. Referring to the hypothesis concerning the role of high melting-point fatty acids of phosphatidylglicerol molecular species in chilling sensitivity the data are presented against generalization of this hypothesis.

scholarly journals Analog Electronic Circuits to Model Cooperativity in Hill Process

2020 ◽  
Vol 39 (4) ◽  
pp. 678-685
Author(s):  
Maria Waqas ◽  
Muhammad Khurram ◽  
S.M. Razaul Hasan
Keyword(s):  
Chemical Reactions ◽  
Electronic Circuit ◽  
Main Idea ◽  
Receptor Site ◽  
The Other ◽  
Hill Reaction ◽  
Cellular Processes ◽  
Receptor Sites ◽  
Model Dynamics ◽  
The Hill

In the field of computational biology, electronic modeling of bio-cellular processes is in vogue for about a couple of decades. Fast, efficient and scalable electronic mimetics of recurrently found bio-chemical reactions are expected to provide better electronic circuit simulators that can also be used as bio-sensors or implantable biodevices at cellular levels. This paper presents some possible electronic circuit equivalents to model dynamics of one such bio-chemical reaction commonly involved in many bio-cellular processes, specifically pathways in living cells, known as the Hill process. The distinguishing feature of this process is cooperativity which has been modeled in silicon substrate using a pair of transistors, one transistor driving current in the other the same way ligand binding to one receptor site controls the binding affinity of the other receptor sites. Two possible circuits have been proposed and compared to electronically model cooperativity of a Hill reaction. The main idea is to exploit the natural analogies found between structures and processes of a bio-cell and electronic transistor mechanics, to efficiently model fundamental bio-chemical reactions found recurring in bio-processes. These circuits can then be combined and rearranged quickly to form larger, more complex bio-networks, thus mitigating the intricacies involved in modeling of such systems.

Cyanoacrylate Inhibitors of the Hill Reaction V. The Effect of Chirality on Inhibitor Binding

1987 ◽  
Vol 42 (6) ◽  
pp. 684-689 ◽  
Author(s):  
John L. Huppatz ◽  
John N. Phillips
Keyword(s):  
Phenyl Ring ◽  
Alkyl Substituent ◽  
Receptor Site ◽  
Optically Active ◽  
Hill Reaction ◽  
Inhibitor Binding ◽  
Level Of Activity ◽  
The Difference ◽  
The Hill

Optically active α-methylbenzylamino 2-cyanoacrylic esters were synthesized and assayed as inhibitors of the Hill reaction in isolated pea chloroplast fragments. The 5-isomers were more potent inhibitors than the S-isomers with discriminations of from ten to greater than 100-fold being observed. A β-alkyl substituent in the cyanoacrylate molecule affected both the level of activity and the difference in activity between the isomers. An α,α-dimethylbenzylamino derivative was also active at about the same level as the corresponding α-methylbenzylamino racemate. This result could be explained in terms of the orientation of the phenyl ring in the receptor site. Replacement of the α-methylbenzylamino group by other α-alkyl and α-phenyl substituents had little effect on activity. However, an α-benzyl group was beneficial.

scholarly journals The Respiration of some Planktonic copepods II. The Effect Of Temperature

1953 ◽  
Vol 31 (3) ◽  
pp. 447-460 ◽  
Author(s):  
D. T. Gauld ◽  
J. E. G. Raymont
Keyword(s):  
Respiratory Rate ◽  
The Body ◽  
The Other ◽  
Effect Of Temperature ◽  
Acartia Clausi ◽  
Temora Longicornis ◽  
Different Temperatures ◽  
Planktonic Copepods ◽  
The Difference ◽  
The Relationship

The respiratory rates of three species of planktonic copepods, Acartia clausi, Centropages hamatus and Temora longicornis, were measured at four different temperatures.The relationship between respiratory rate and temperature was found to be similar to that previously found for Calanus, although the slope of the curves differed in the different species.The observations on Centropages at 13 and 170 C. can be divided into two groups and it is suggested that the differences are due to the use of copepods from two different generations.The relationship between the respiratory rates and lengths of Acartia and Centropages agreed very well with that previously found for other species. That for Temora was rather different: the difference is probably due to the distinct difference in the shape of the body of Temora from those of the other species.The application of these measurements to estimates of the food requirements of the copepods is discussed.

The Germans and Air Power at Dieppe: The Raid and its Lessons from the ‘Other Side of the Hill’

2021 ◽  
pp. 096834452199586
Author(s):  
James Shelley
Keyword(s):  
Armed Forces ◽  
The Other ◽  
Air Power ◽  
Coastal Defence ◽  
German Armed Forces ◽  
Popular Interest ◽  
The Hill

Despite the vast academic and popular interest in the Dieppe raid of 19 August 1942, there remains a curious oversight of the German side of the story. This contribution interrogates German sources in order to explore the Dieppe air battle and its consequences from the perspective of the German armed forces. The paper ultimately demonstrates that the Germans learnt much about the role of air power in coastal defence from their experiences at Dieppe, but that the implementation of those lessons was lacking.

Interaction of Photosystem II Herbicides with Bicarbonate and Formate in Their Effects on Photosynthetic Electron Flow

1984 ◽  
Vol 39 (5) ◽  
pp. 374-377 ◽  
Author(s):  
J. J. S. van Rensen
Keyword(s):  
Electron Transport ◽  
Photosystem Ii ◽  
Electron Flow ◽  
Photosynthetic Electron Transport ◽  
Hill Reaction ◽  
Amaranthus Hybridus ◽  
Apparent Affinity ◽  
Photosynthetic Electron Flow ◽  
Different Characteristics ◽  
The Hill

The reactivation of the Hill reaction in CO2-depleted broken chloroplasts by various concentrations of bicarbonate was measured in the absence and in the presence of photosystem II herbicides. It appears that these herbicides decrease the apparent affinity of the thylakoid membrane for bicarbonate. Different characteristics of bicarbonate binding were observed in chloroplasts of triazine-resistant Amaranthus hybridus compared to the triazine-sensitive biotype. It is concluded that photosystem II herbicides, bicarbonate and formate interact with each other in their binding to the Qв-protein and their interference with photosynthetic electron transport.

Metabolism of a Pyrrolidine Urea Herbicide in Corn and Weeds

Weed Science ◽  
1974 ◽  
Vol 22 (1) ◽  
pp. 10-14 ◽  
Author(s):  
R. E. Holm ◽  
D. E. Stallard
Keyword(s):  
Adventitious Roots ◽  
Parent Compound ◽  
Soil Surface ◽  
Abutilon Theophrasti ◽  
Water Soluble ◽  
Hill Reaction ◽  
Panicum Miliaceum ◽  
Proso Millet ◽  
Ipomoea Purpurea ◽  
The Hill

Five 2,5-dimethyl-1-pyrrolidinecarboxanilides were effective inhibitors of the Hill reaction. However, only thecisisomers were active; thetransisomers were totally inactive. Experiments were conducted using14C-5328 (cis-2,5-dimethyl-1-pyrrolidinecarboxanilide). A correlation existed between resistance of various plants to 5328 and their ability to metabolize it to water soluble metabolites. Velvetleaf (Abutilon theophrastiMedic.) and proso millet (Panicum miliaceumL.) seedlings were very susceptible to 5328 and were unable to metabolize it. Tall morningglory [Ipomoea purpurea(L.) Roth] seedlings were highly tolerant to 5328 and converted it completely to its metabolites. Corn (Zea maysL. ‘DeKalb variety XL-45′) seedlings which were slightly susceptible to 5328 injury were able to metabolize up to 90% of the parent compound. Corn foliage uptake of14C-5328 applied to the soil surface occurred through the adventitious roots.

scholarly journals Effect of Temperature on the Corrosion Inhibition of Trans-4-Hydroxy-4′-Stilbazole on Mild Steel in HCl Solution

2012 ◽  
Vol 2012 ◽  
pp. 1-7 ◽  
Author(s):  
Ayssar Nahlé ◽  
Ideisan I. Abu-Abdoun ◽  
Ibrahim Abdel-Rahman
Keyword(s):  
Weight Loss ◽  
Double Bond ◽  
Adsorption Isotherm ◽  
Mild Steel ◽  
Corrosion Inhibitor ◽  
Thermodynamic Parameters ◽  
The Other ◽  
Effect Of Temperature ◽  
Temkin Adsorption Isotherm ◽  
Hcl Solution

The inhibition and the effect of temperature and concentration of trans-4-hydroxy-4′-stilbazole on the corrosion of mild steel in 1 M HCl solution was investigated by weight loss experiments at temperatures ranging from 303 to 343 K. The studied inhibitor concentrations were between  M and  M. The percentage inhibition increased with the increase of the concentration of the inhibitor. The percentage inhibition reached about 94% at the concentration of  M and 303 K. On the other hand, the percentage inhibition decreased with the increase of temperature. Using the Temkin adsorption isotherm, the thermodynamic parameters for the adsorption of this inhibitor on the metal surface were calculated. Trans-4-hydroxy-4′-stilbazole was found to be a potential corrosion inhibitor since it contained not only nitrogen and oxygen, but also phenyl and pyridine rings that are joined together with a double bond (–C=C–) in conjugation with these rings.

scholarly journals Sex Differentiation in Amphibians: Effect of Temperature and Its Influence on Sex Reversal

2021 ◽  
pp. 1-11
Author(s):  
Adrián Ruiz-García ◽  
Álvaro S. Roco ◽  
Mónica Bullejos
Keyword(s):  
Sexual Differentiation ◽  
Sex Differentiation ◽  
Environmental Contaminants ◽  
Natural Populations ◽  
Sex Reversal ◽  
The Other ◽  
Effect Of Temperature ◽  
Amphibian Species ◽  
Expected Increase

The role of environmental factors in sexual differentiation in amphibians is not new. The effect of hormones or hormone-like compounds is widely demonstrated. However, the effect of temperature has traditionally been regarded as something anecdotal that occurs in extreme situations and not as a factor to be considered. The data currently available reveal a different situation. Sexual differentiation in some amphibian species can be altered even by small changes in temperature. On the other hand, although not proven, it is possible that temperature is related to the appearance of sex-reversed individuals in natural populations under conditions unrelated to environmental contaminants. According to this, temperature, through sex reversal (phenotypic sex opposed to genetic sex), could play an important role in the turnover of sex-determining genes and in the maintenance of homomorphic sex chromosomes in this group. Accordingly, and given the expected increase in global temperatures, growth and sexual differentiation in amphibians could easily be affected, altering the sex ratio in natural populations and posing major conservation challenges for a group in worldwide decline. It is therefore particularly urgent to understand the mechanism by which temperature affects sexual differentiation in amphibians.

scholarly journals Studies on the Second Emerson Effect in the Hill Reaction in Algal Cells

1961 ◽  
Vol 1 (5) ◽  
pp. 377-388 ◽  
Author(s):  
Rajni Govindjee ◽  
Eugene Rabinowitch
Keyword(s):  
Hill Reaction ◽  
The Hill
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