scholarly journals Flooding tolerance: suites of plant traits in variable environments

2009 ◽  
Vol 36 (8) ◽  
pp. 665 ◽  
Author(s):  
T. D. Colmer ◽  
L. A. C. J. Voesenek
Keyword(s):  
Plant Traits ◽  
Anoxia Tolerance ◽  
Submergence Tolerance ◽  
Low Oxygen ◽  
Adaptive Traits ◽  
Soil Waterlogging ◽  
Long Duration ◽  
Variable Environments ◽  
Different Depths ◽  
Oxygen Escape

Flooding regimes of different depths and durations impose selection pressures for various traits in terrestrial wetland plants. Suites of adaptive traits for different flooding stresses, such as soil waterlogging (short or long duration) and full submergence (short or long duration – shallow or deep), are reviewed. Synergies occur amongst traits for improved internal aeration, and those for anoxia tolerance and recovery, both for roots during soil waterlogging and shoots during submergence. Submergence tolerance of terrestrial species has recently been classified as either the Low Oxygen Quiescence Syndrome (LOQS) or the Low Oxygen Escape Syndrome (LOES), with advantages, respectively, in short duration or long duration (shallow) flood-prone environments. A major feature of species with the LOQS is that shoots do not elongate upon submergence, whereas those with the LOES show rapid shoot extension. In addition, plants faced with long duration deep submergence can demonstrate aspects of both syndromes; shoots do not elongate, but these are not quiescent, as new aquatic-type leaves are formed. Enhanced entries of O2 and CO2 from floodwaters into acclimated leaves, minimises O2 deprivation and improves underwater photosynthesis, respectively. Evolution of ‘suites of traits’ are evident in wild wetland species and in rice, adapted to particular flooding regimes.

scholarly journals The Mce3R stress-resistance pathway is vulnerable to small-molecule targeting that improves tuberculosis drug activities

2019 ◽  
Author(s):  
Xinxin Yang ◽  
Tianao Yuan ◽  
Rui Ma ◽  
Kieran Chacko ◽  
Melissa Smith ◽  
...  
Keyword(s):  
Small Molecule ◽  
Stress Resistance ◽  
Inhibitory Concentration ◽  
Infectious Agent ◽  
Low Oxygen ◽  
Long Duration ◽  
Resistance Pathway ◽  
Oxygen Conditions ◽  
Drug Regimens ◽  
High Doses

<p>One-third of the world’s population carries <i>Mycobacterium tuberculosis </i>(<i>Mtb</i>), the infectious agent that causes tuberculosis (TB), and every 17 seconds someone dies of TB. After infection, <i>Mtb</i>can live dormant within macrophages for decades in a granuloma structure arising from the host immune response; and cholesterol is important for this persistence of <i>Mtb</i>. Current treatments require long-duration drug regimens with many associated toxicities, which are compounded by the high doses required. We phenotypically screened 35 6-azasteroid analogues against <i>Mtb</i>and found that at low micromolar concentrations, a subset of the <a>analogues sensitized <i>Mtb</i></a>to multiple TB drugs. Two analogues were selected for further study to characterize the bactericidal activity of bedaquiline and isoniazid under normoxic and low-oxygen conditions. These two 6-azasteroids <a>showed strong synergy with bedaquiline</a>(fractional inhibitory concentration index = 0.21, bedaquiline minimal inhibitory concentration = 16 nM at 1 μM 6-azasteroid). The rate at which spontaneous resistance to one of the 6-azasteroids arose in the presence of bedaquiline was approximately 10<sup>−9</sup>, and the 6-azasteroid-resistant mutants retained their isoniazid and bedaquiline sensitivity. Genes in the cholesterol-regulated Mce3R regulon were required for 6-azasteroid activity, whereas genes in the cholesterol catabolism pathway were not. Expression of a subset of Mce3R genes was down-regulated upon 6-azasteroid treatment. The Mce3R regulon is implicated in stress resistance and is absent in saprophytic mycobacteria. This regulon encodes a cholesterol-regulated stress-resistance pathway that we conclude is important for pathogenesis and contributes to drug tolerance, and that this pathway is vulnerable to small-molecule targeting in live mycobacteria.</p>

Organisms and their Interactions

2018 ◽  
Author(s):  
Karen J. Esler ◽  
Anna L. Jacobsen ◽  
R. Brandon Pratt
Keyword(s):  
Plant Traits ◽  
Root Nodules ◽  
Cluster Roots ◽  
Adaptive Traits ◽  
Evolutionary Patterns ◽  
Plant Seed ◽  
Herbivore Interactions ◽  
Plant Herbivore ◽  
Nutrient Extraction ◽  
Plant Pollinator

Both animal and plant species exhibit adaptive traits related to features of mediterranean-type ecosystems (MTEs). For plants, the seasonality of the MTC has been an important factor in the evolution of plant phenological traits. Root adaptive traits that improve nutrient extraction from impoverished soils are present within MTC regions, including cluster roots, root nodules, and mycorrhizal symbioses. Fire has been an important driver of plant traits, such as smoke, charate, or heat-induced seed germination or seed release (i.e. serotiny), and post-fire flowering. Adaptive traits in animals include both physiological and behavioural traits. MTC regions have been used in the study of many ecological and evolutionary patterns, particularly as related to organismal adaptations to unique soil and substrates (edaphic communities) and interactions between plants and animals, such as plant–herbivore interactions, plant–pollinator interactions, and plant–seed disperser interactions. These interactions shape many plant and animal characters within MTC regions.

scholarly journals 1001 ANOXIA TOLERANCE OF MAIZE SEEDLING ROOTS

HortScience ◽  
1994 ◽  
Vol 29 (5) ◽  
pp. 573a-573
Author(s):  
B. G. Cobb ◽  
D. L. Andrews ◽  
D. M. MacAlpine ◽  
J. R. Johnson ◽  
M. C. Drew
Keyword(s):  
Alcoholic Fermentation ◽  
Seedling Emergence ◽  
Primary Root ◽  
Maize Seedling ◽  
Anoxia Tolerance ◽  
Maize Seedlings ◽  
Low Oxygen ◽  
Oxygen Stress ◽  
Stages Of Growth ◽  
Seedling Roots

We have been examining the response of maize seedling roots to oxygen stress. Previously, we have shown that maize seedlings with primary root lengths of 10cm or greater require a pretreatment with low oxygen (hypoxia) for survival of greater than 12 hours of anoxia. During the pretreatment there is induction of mRNA and increase in enzymatic activity of alcohol dehydrogenase (ADH) and other enzymes that are necessary for alcoholic fermentation. However, we have found that younger seedlings do not need a pretreatment to survive anoxia. They appear to have high levels of ADH and other enzymes that are needed for anaerobic survival at levels equivalent to those that are induced in older seedlings. These results suggest that, at the time of seedling emergence, seedlings may be more adapted to oxygen stress than during later stages of growth.

scholarly journals Genetic variability of submergence tolerance in rice related to yield and yield contributing traits

1970 ◽  
pp. 22-27
Author(s):  
Md Rafiqul Islam
Keyword(s):  
Grain Yield ◽  
Short Duration ◽  
Plant Traits ◽  
Function Analysis ◽  
Genotypic Variation ◽  
Multivariate Techniques ◽  
Submergence Tolerance ◽  
Maximum Variance ◽  
Spikelets Per Panicle ◽  
Panicle Weight

Twenty-three rice genotypes were evaluated during kharif II season for understanding the submergence tolerance associated with short-duration and high yielding traits. For this, relative performance of seven quantitative plant traits of the genotypes viz. days to maturity, panicles per hill, panicle weight, spikelets sterility, spikelets per panicle, 1000-seed weight and grain yield were analyzed under normal and submerged conditions. The genotypic variation was found in all the relative plant traits. Multivariate techniques viz. k-means cluster analysis and discriminant function analysis (DFA) were used for grouping the genotypes. Maximum number of genotypes (15) were grouped in cluster 3 followed by cluster 1 (4). The genotype BRRI dhan31, BRRI dhan39, BRRI dhan56 and BRRI dhan57 under cluster 1 performed better compared to other cluster members. DFA showed that function 1 and 2 explained 80.5 percent and 16.9 percent respectively with a cumulative of 97.4 percent of total variance of the genotypes. Panicles per hill, panicle weight, sterility percent, 1000-grain weight and grain yield mostly contributed in grouping the genotypes. The panicle weight followed by grain yield played the major role for the maximum variance in the genotypes. The results suggest that the short-duration genotypes BRRI dhan33 and BRRI dhan56 and BRRI dhan57 performed better under submerged condition and the plant traits like panicle weight or grain yield could be the best choice for submergence tolerance in rice.

scholarly journals The Mce3R stress-resistance pathway is vulnerable to small-molecule targeting that improves tuberculosis drug activities

2019 ◽  
Author(s):  
Xinxin Yang ◽  
Tianao Yuan ◽  
Rui Ma ◽  
Kieran Chacko ◽  
Melissa Smith ◽  
...  
Keyword(s):  
Small Molecule ◽  
Stress Resistance ◽  
Inhibitory Concentration ◽  
Infectious Agent ◽  
Low Oxygen ◽  
Long Duration ◽  
Resistance Pathway ◽  
Oxygen Conditions ◽  
Drug Regimens ◽  
High Doses

<p>One-third of the world’s population carries <i>Mycobacterium tuberculosis </i>(<i>Mtb</i>), the infectious agent that causes tuberculosis (TB), and every 17 seconds someone dies of TB. After infection, <i>Mtb</i>can live dormant within macrophages for decades in a granuloma structure arising from the host immune response; and cholesterol is important for this persistence of <i>Mtb</i>. Current treatments require long-duration drug regimens with many associated toxicities, which are compounded by the high doses required. We phenotypically screened 35 6-azasteroid analogues against <i>Mtb</i>and found that at low micromolar concentrations, a subset of the <a>analogues sensitized <i>Mtb</i></a>to multiple TB drugs. Two analogues were selected for further study to characterize the bactericidal activity of bedaquiline and isoniazid under normoxic and low-oxygen conditions. These two 6-azasteroids <a>showed strong synergy with bedaquiline</a>(fractional inhibitory concentration index = 0.21, bedaquiline minimal inhibitory concentration = 16 nM at 1 μM 6-azasteroid). The rate at which spontaneous resistance to one of the 6-azasteroids arose in the presence of bedaquiline was approximately 10<sup>−9</sup>, and the 6-azasteroid-resistant mutants retained their isoniazid and bedaquiline sensitivity. Genes in the cholesterol-regulated Mce3R regulon were required for 6-azasteroid activity, whereas genes in the cholesterol catabolism pathway were not. Expression of a subset of Mce3R genes was down-regulated upon 6-azasteroid treatment. The Mce3R regulon is implicated in stress resistance and is absent in saprophytic mycobacteria. This regulon encodes a cholesterol-regulated stress-resistance pathway that we conclude is important for pathogenesis and contributes to drug tolerance, and that this pathway is vulnerable to small-molecule targeting in live mycobacteria.</p>

scholarly journals The Mce3R stress-resistance pathway is vulnerable to small-molecule targeting that improves tuberculosis drug activities

2019 ◽  
Author(s):  
Xinxin Yang ◽  
Tianao Yuan ◽  
Rui Ma ◽  
Kieran Chacko ◽  
Melissa Smith ◽  
...  
Keyword(s):  
Small Molecule ◽  
Stress Resistance ◽  
Inhibitory Concentration ◽  
Infectious Agent ◽  
Low Oxygen ◽  
Long Duration ◽  
Resistance Pathway ◽  
Oxygen Conditions ◽  
Drug Regimens ◽  
High Doses

<p>One-third of the world’s population carries <i>Mycobacterium tuberculosis </i>(<i>Mtb</i>), the infectious agent that causes tuberculosis (TB), and every 17 seconds someone dies of TB. After infection, <i>Mtb</i>can live dormant within macrophages for decades in a granuloma structure arising from the host immune response; and cholesterol is important for this persistence of <i>Mtb</i>. Current treatments require long-duration drug regimens with many associated toxicities, which are compounded by the high doses required. We phenotypically screened 35 6-azasteroid analogues against <i>Mtb</i>and found that at low micromolar concentrations, a subset of the <a>analogues sensitized <i>Mtb</i></a>to multiple TB drugs. Two analogues were selected for further study to characterize the bactericidal activity of bedaquiline and isoniazid under normoxic and low-oxygen conditions. These two 6-azasteroids <a>showed strong synergy with bedaquiline</a>(fractional inhibitory concentration index = 0.21, bedaquiline minimal inhibitory concentration = 16 nM at 1 μM 6-azasteroid). The rate at which spontaneous resistance to one of the 6-azasteroids arose in the presence of bedaquiline was approximately 10<sup>−9</sup>, and the 6-azasteroid-resistant mutants retained their isoniazid and bedaquiline sensitivity. Genes in the cholesterol-regulated Mce3R regulon were required for 6-azasteroid activity, whereas genes in the cholesterol catabolism pathway were not. Expression of a subset of Mce3R genes was down-regulated upon 6-azasteroid treatment. The Mce3R regulon is implicated in stress resistance and is absent in saprophytic mycobacteria. This regulon encodes a cholesterol-regulated stress-resistance pathway that we conclude is important for pathogenesis and contributes to drug tolerance, and that this pathway is vulnerable to small-molecule targeting in live mycobacteria.</p>

scholarly journals Evaluating a Lithium-Seawater Battery on Gliders

2017 ◽  
Vol 34 (5) ◽  
pp. 1175-1182 ◽  
Author(s):  
Russ E. Davis ◽  
Jeffrey T. Sherman
Keyword(s):  
Mass Transfer ◽  
Oxygen Concentration ◽  
Current Density ◽  
Flow Conditions ◽  
Low Oxygen ◽  
Lithium Ions ◽  
Neutral Buoyancy ◽  
Underwater Gliders ◽  
Long Duration ◽  
Seawater Battery

AbstractNeutral-buoyancy vehicles demand high-density energy sources and lithium is light with high oxidation energy. PolyPlus Battery Company has developed a prototype lithium-seawater battery that is attractive for powering long-duration autonomous oceanographic vehicles (floats and underwater gliders). These batteries were tested in the laboratory and at sea.PolyPlus batteries use “Protected Lithium Electrodes” with proprietary “windows” protecting the volatile lithium anode from water while passing lithium ions. The cathode reduces oxygen dissolved in seawater, or hydrolyzes seawater to produce hydrogen. Not requiring additional electrolyte, fuel, or pressure cases, these cells have impressive weight advantages. Good electrode–seawater mass transfer is required but can increase drag and be impeded by biofouling.Tests assessing robustness of the PolyPlus batteries in oceanographic use, evaluating mass transfer issues, and observing biofouling impacts are reported. In sea trials, two cells were tested for 69 days mounted on a Spray glider. Findings are as follows: 1) the cells were robust over 900 dives, most to 400 m; 2) without antifouling measures, the cells became substantially biofouled, but their performance was undiminished; and 3) performance was complex, depending on current density, oxygen concentration, and flow conditions. For dissolved oxygen concentration above 1 mL L−1, the cells delivered 9 W m−2 of electrode surface at 3 V. For low oxygen, the cell shifted to hydrolysis near 2.3 V, but mass transfer was less critical so current density could be increased and observed power reached 5 W m−2. This could be increased using a lower resistance load.

Temperature studies using positron lifetime spectroscopy of the subsurface zone in pure titanium exposed to a dry sliding test

2021 ◽  
pp. 135065012110605
Author(s):  
Jerzy Dryzek
Keyword(s):  
Positron Lifetime ◽  
Pure Titanium ◽  
Dry Sliding ◽  
Vacancy Clusters ◽  
Long Period ◽  
Subsurface Zone ◽  
Long Duration ◽  
Different Depths ◽  
Positron Lifetime Spectroscopy ◽  
Sliding Test

The report presents the positron annihilation studies of subsurface zone generated in pure titanium exposed to a long period dry sliding test. The total depth of the subsurface zone induced is detected at about 250 µm. Only dislocations and vacancy clusters which consist of two or three vacancies are observed in this zone. Their concentration decreases with the depth, especially at the depth above 100 µm. Despite the long duration of the sliding test, no clear signs indicating the presence of a tribolayer were observed. This was confirmed also by observation of annealing of defects in this zone at different depths. The lack of the tribolayer is in contrast to the research done so far for other metals.

scholarly journals Sources of Uncertainty in Precipitation-Type Forecasting

2014 ◽  
Vol 29 (4) ◽  
pp. 936-953 ◽  
Author(s):  
Heather Dawn Reeves ◽  
Kimberly L. Elmore ◽  
Alexander Ryzhkov ◽  
Terry Schuur ◽  
John Krause
Keyword(s):  
Model Uncertainty ◽  
Temperature Profiles ◽  
Model Forecast ◽  
Freezing Rain ◽  
Algorithm Performance ◽  
Sources Of Uncertainty ◽  
Long Duration ◽  
Variable Environments ◽  
Precipitation Type

Abstract Five implicit precipitation-type algorithms are assessed using observed and model-forecast sounding data in order to measure their accuracy and to gauge the effects of model uncertainty on algorithm performance. When applied to observed soundings, all algorithms provide very reliable guidance on snow and rain (SN and RA). However, their skills for ice pellets and freezing rain (IP and FZRA) are comparatively low. Most misclassifications of IP are for FZRA and vice versa. Deeper investigation reveals that no method used in any of the algorithms to differentiate between IP and FZRA allows for clear discrimination between the two forms. The effects of model uncertainty are also considered. For SN and RA, these effects are minimal and each algorithm performs reliably. Conversely, IP and FZRA are strongly impacted. When the range of uncertainty is fully accounted for, their resulting wet-bulb temperature profiles are nearly indistinguishable, leading to very poor skill for all algorithms. Although currently available data do not allow for a thorough investigation, comparison of the statistics from only those soundings that are associated with long-duration, horizontally uniform regions of FZRA shows there are significant differences between these profiles and those that are from more transient, highly variable environments. Hence, a five-category (SN, RA, IP, FZRA, and IP–FZRA mix) approach is advocated to differentiate between sustained regions of horizontally uniform FZRA (or IP) from more mixed environments.

The LDE-Type Flare Occurrence (1969-1993)

1994 ◽  
Vol 144 ◽  
pp. 279-282
Author(s):  
A. Antalová
Keyword(s):  
Time Series ◽  
Fourier Analysis ◽  
Sunspot Cycle ◽  
List Type ◽  
Type Number ◽  
Solar Cycles ◽  
Type Iv ◽  
Long Duration ◽  
Cycle Maximum ◽  
Flare Index

AbstractThe occurrence of LDE-type flares in the last three cycles has been investigated. The Fourier analysis spectrum was calculated for the time series of the LDE-type flare occurrence during the 20-th, the 21-st and the rising part of the 22-nd cycle. LDE-type flares (Long Duration Events in SXR) are associated with the interplanetary protons (SEP and STIP as well), energized coronal archs and radio type IV emission. Generally, in all the cycles considered, LDE-type flares mainly originated during a 6-year interval of the respective cycle (2 years before and 4 years after the sunspot cycle maximum). The following significant periodicities were found:• in the 20-th cycle: 1.4, 2.1, 2.9, 4.0, 10.7 and 54.2 of month,• in the 21-st cycle: 1.2, 1.6, 2.8, 4.9, 7.8 and 44.5 of month,• in the 22-nd cycle, till March 1992: 1.4, 1.8, 2.4, 7.2, 8.7, 11.8 and 29.1 of month,• in all interval (1969-1992):a)the longer periodicities: 232.1, 121.1 (the dominant at 10.1 of year), 80.7, 61.9 and 25.6 of month,b)the shorter periodicities: 4.7, 5.0, 6.8, 7.9, 9.1, 15.8 and 20.4 of month.Fourier analysis of the LDE-type flare index (FI) yields significant peaks at 2.3 - 2.9 months and 4.2 - 4.9 months. These short periodicities correspond remarkably in the all three last solar cycles. The larger periodicities are different in respective cycles.

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