Influence of water potential on the survival and saprophytic activity of Rhizoctonia solani AG 4 in natural soil

1985 ◽  
Vol 63 (12) ◽  
pp. 2364-2368 ◽  
Author(s):  
R. C. Ploetz ◽  
D. J. Mitchell
Keyword(s):  
Rhizoctonia Solani ◽  
Water Potential ◽  
Fine Sand ◽  
Natural Soil ◽  
Intermediate Water ◽  
Water Potentials ◽  
Influence Of Water ◽  
General Survival

The survival of Rhizoctonia solani AG 4 was monitored in a natural Arredondo fine sand incubated under controlled water potentials. In general, survival was greater in soils held at intermediate water potentials of −2 to −15 bars (1 bar = 100 kPa) than in moister or drier soils. Saprophytic colonization of rye stem pieces by R. solani AG 4 in artificially infested, natural soil occurred at five water potentials ranging from −0.05 to −15 bars. Colonization did not occur at −1500 bars. Maximum colonization at any of the former water potentials was detected 1 or 2 days after the beginning of an experiment, but it decreased rapidly after 3 days.

A preliminary study of the influence of water potential on sclerotium germination in Sclerotinia sclerotiorum

1977 ◽  
Vol 55 (1) ◽  
pp. 8-11 ◽  
Author(s):  
R. A. A. Morrall
Keyword(s):  
Polyethylene Glycol ◽  
Water Potential ◽  
Sclerotinia Sclerotiorum ◽  
Clay Soil ◽  
Semipermeable Membrane ◽  
Water Potentials ◽  
Heavy Clay ◽  
Influence Of Water ◽  
Preliminary Study

Sclerotia of Sclerotinia sclerotiorum (Lib.) de Bary buried in a heavy clay soil at 15 °C germinated over a range of moisture levels from 15% to 50%. A method of germinating sclerotia held at constant matric water potentials was tested. Sclerotia were placed in soil in bags of a semipermeable membrane; the bags were immersed in solutions of polyethylene glycol 20 000.Germination occurred between 0 and −7.5 bars but not at lower potentials.

INFLUENCE OF WATER POTENTIAL ON GROWTH, ANTIBIOTIC PRODUCTION, AND SURVIVAL OF CEPHALOSPORIUM GRAMINEUM

1972 ◽  
Vol 52 (4) ◽  
pp. 417-423 ◽  
Author(s):  
G. W. BRUEHL ◽  
B. CUNFER ◽  
M. TOIVIAINEN
Keyword(s):  
Water Potential ◽  
Soil Fungi ◽  
Antibiotic Production ◽  
Saturated Soil ◽  
Water Potentials ◽  
Osmotic Water ◽  
Influence Of Water ◽  
Agar Media ◽  
Water Saturated ◽  
Cephalosporium Gramineum

Cephalosporium gramineum grew on agar media at osmotic water potentials from − 1.3 bars to between − 98 and − 112 bars. The growth of antibiotic-producing (+) and nonproducing (−) isolates was affected equally by water potential. Antibiotic production was detected by bioassay over the entire range of significant growth (to about − 83 to − 98 bars). Production of antibiotic relative to the growth rate of C. gramineum was least when the fungus grew fastest and most when the fungus was under moderate water stress (between − 27 and − 55 bars). When straws infested with C. gramineum were incubated on soil at 15 C at various water potentials, + isolates had the least advantage over − isolates on water-saturated soil (near 0 bar) and at the driest condition tested (−258 bars). In contrast, antibiotic-producing isolates had the greatest survival advantage between − 10 and − 67 bars, which corresponds to the range of water potentials within which antibiotic production was greatest relative to mycelial growth. The vigor of C. gramineum in straw on water-saturated soil indicates coexistence with bacteria; its performance between about − 10 and − 137 bars indicates that relatively xerophytic soil fungi are its most severe antagonists in nature.

NITROGEN TRANSFORMATIONS NEAR UREA IN SOIL WITH DIFFERENT WATER POTENTIALS

1988 ◽  
Vol 68 (3) ◽  
pp. 569-576 ◽  
Author(s):  
YADVINDER SINGH ◽  
E. G. BEAUCHAMP
Keyword(s):  
Water Potential ◽  
Soil Water ◽  
Incubation Period ◽  
Relative Rate ◽  
Soil Water Potential ◽  
Nitrification Inhibitor ◽  
Silt Loam ◽  
Nitrogen Transformations ◽  
Water Potentials ◽  
Initial Soil

Two laboratory incubation experiments were conducted to determine the effect of initial soil water potential on the transformation of urea in large granules to nitrite and nitrate. In the first experiment two soils varying in initial soil water potentials (− 70 and − 140 kPa) were incubated with 2 g urea granules with and without a nitrification inhibitor (dicyandiamide) at 15 °C for 35 d. Only a trace of [Formula: see text] accumulated in a Brookston clay (pH 6.0) during the transformation of urea in 2 g granules. Accumulation of [Formula: see text] was also small (4–6 μg N g−1) in Conestogo silt loam (pH 7.6). Incorporation of dicyandiamide (DCD) into the urea granule at 50 g kg−1 urea significantly reduced the accumulation of [Formula: see text] in this soil. The relative rate of nitrification in the absence of DCD at −140 kPa water potential was 63.5% of that at −70 kPa (average of two soils). DCD reduced the nitrification of urea in 2 g granules by 85% during the 35-d period. In the second experiment a uniform layer of 2 g urea was placed in the center of 20-cm-long cores of Conestogo silt loam with three initial water potentials (−35, −60 and −120 kPa) and the soil was incubated at 15 °C for 45 d. The rate of urea hydrolysis was lowest at −120 kPa and greatest at −35 kPa. Soil pH in the vicinity of the urea layer increased from 7.6 to 9.1 and [Formula: see text] concentration was greater than 3000 μg g−1 soil. There were no significant differences in pH or [Formula: see text] concentration with the three soil water potential treatments at the 10th day of the incubation period. But, in the latter part of the incubation period, pH and [Formula: see text] concentration decreased with increasing soil water potential due to a higher rate of nitrification. Diffusion of various N species including [Formula: see text] was probably greater with the highest water potential treatment. Only small quantities of [Formula: see text] accumulated during nitrification of urea – N. Nitrification of urea increased with increasing water potential. After 35 d of incubation, 19.3, 15.4 and 8.9% of the applied urea had apparently nitrified at −35, −60 and −120 kPa, respectively. Nitrifier activity was completely inhibited in the 0- to 2-cm zone near the urea layer for 35 days. Nitrifier activity increased from an initial level of 8.5 to 73 μg [Formula: see text] in the 3- to 7-cm zone over the 35-d period. Nitrifier activity also increased with increasing soil water potential. Key words: Urea transformation, nitrification, water potential, large granules, nitrifier activity, [Formula: see text] production

Photosynthesis Response of Sunlit and Shade Pepper (Capsicum annuum) Leaves at Different Positions in the Canopy Under Two Water Regimes

1994 ◽  
Vol 21 (3) ◽  
pp. 377 ◽  
Author(s):  
A Alvino ◽  
M Centritto ◽  
FD Lorenzi
Keyword(s):  
Water Potential ◽  
Capsicum Annuum ◽  
Leaf Water Potential ◽  
Co2 Exchange ◽  
Leaf Water ◽  
Predawn Leaf Water Potential ◽  
Water Regimes ◽  
Water Potentials ◽  
Sun And Shade ◽  
Shade Leaves

Pepper (Capsicum annuum L.) plants were grown in 1 m2 lysimeters under two different water regimes in order to investigate differences in the spatial arrangements of the leaves and to relate this to daily assimilation rates of leaves of the canopy. The control regime (well-watered (W) treatment) was irrigated whenever the accumulated 'A' pan evaporation reached 4 cm, whereas the water-stressed (S) treatment was watered whenever the predawn leaf water potential fell below -1 MPa. During the growing cycle, equal numbers of sun and shade leaves were chosen from the apical, middle and basal parts of the canopy, corresponding to groups of leaves of increasing age. The CO2 exchange rate (CER) was measured at 0830, 1230 and 1530 hours on 8 days along the crop cycle, on leaves in their natural inclination and orientation. Leaf water potentials were measured on apical leaves before dawn and concurrently with gas exchange measurements. Control plants maintained predawn leaf water potential at -0.3 MPa, but S plants reached values lower than -1.2 MPa. Midday leaf water potentials were about twice as low in the S plants as in the controls. Water stress reduced LA1 during the period of crop growth, and dry matter production at harvest. Stressed apical leaves appeared to reduce stress by changing their inclination. They were paraheliotropic around midday and diaheliotropic at 0830 and 1530 hours. The CER values of the S treatment were significantly lower than those of the W treatment in apical and middle leaves, whereas the CER of basal leaves did not differ in either treatments. In the S treatment, reduction in the CER values of sunlit apical leaves was more evident in the afternoon than at midday or early in the morning, whereas basal leaves were less affected by water than basal stress leaves if sunlit, and negligibly in shaded conditions.

scholarly journals Live-Scale Testing of Granular Materials Stabilized with Alkali-Activated Waste Glass and Carbide Lime

2021 ◽  
Vol 11 (23) ◽  
pp. 11286
Author(s):  
Marina Paula Secco ◽  
Débora Thaís Mesavilla ◽  
Márcio Felipe Floss ◽  
Nilo Cesar Consoli ◽  
Tiago Miranda ◽  
...  
Keyword(s):  
Portland Cement ◽  
Mechanical Performance ◽  
Raw Materials ◽  
Sodium Hydroxide Solution ◽  
Fine Sand ◽  
Field Application ◽  
Natural Soil ◽  
In Situ Tests ◽  
Alkali Activated

The increasingly strong search for alternative materials to Portland cement has resulted in the development of alkali-activated cements (AAC) that are very effective at using industrial by-products as raw materials, which also contributes to the volume reduction in landfilled waste. Several studies targeting the development of AAC—based on wastes containing silicon and calcium—for chemical stabilization of soils have demonstrated their excellent performance in terms of durability and mechanical performance. However, most of these studies are confined to a laboratory characterization, ignoring the influence and viability of the in situ construction process and, also important, of the in situ curing conditions. The present work investigated the field application of an AAC based on carbide lime and glass wastes to stabilize fine sand acting as a superficial foundation. The assessment was supported on the unconfined compressive strength (UCS) and initial shear modulus (G0) of the developed material, and the field results were compared with those prepared in the laboratory, up to 120 days curing. In situ tests were also developed on the field layers (with diameters of 450 and 900 mm and thickness of 300 mm) after different curing times. To establish a reference, the mentioned precursors were either activated with a sodium hydroxide solution or hydrated with water (given the reactivity of the lime). The results showed that the AAC-based mixtures developed greater strength and stiffness at a faster rate than the water-based mixtures. Specimens cured under controlled laboratory conditions showed better results than the samples collected in the field. The inclusion of the stabilized layers clearly increased the load-bearing capacity of the natural soil, while the different diameters produced different failure mechanisms, similar to those found in Portland cement stabilization.

scholarly journals Dehydration of Macromolecules I. Effect of Dehydration-Rehydration on Indoleacetic Acid Oxidase, Ribonuclease, Ribulosediphosphate Carboxylase, and Ketose-1-Phosphate Aldolase

1973 ◽  
Vol 26 (3) ◽  
pp. 591 ◽  
Author(s):  
B Darbyshire ◽  
BT Steer
Keyword(s):  
Water Potential ◽  
Indoleacetic Acid ◽  
Acid Oxidase ◽  
Enzyme Preparations ◽  
Water Potentials ◽  
Membrane Technique ◽  
Indoleacetic Acid Oxidase

A pressure-membrane technique has been developed to physically manipulate the water potential of in vitro enzyme preparations. Enzyme preparations were subjected to a range of water potentials using this technique.

Corrigenda - Measurement of the total water potential of aqueous solutions of polyethylene glycol - A comparison between osmometer, thermocouple psychrometer and equilibrated soil cores

Soil Research ◽  
1993 ◽  
Vol 31 (1) ◽  
pp. 1
Author(s):  
IM Wood ◽  
IK Dart ◽  
HB So
Keyword(s):  
Polyethylene Glycol ◽  
Water Potential ◽  
Close Correlation ◽  
Ease Of Use ◽  
Effect Of Temperature ◽  
Soil Cores ◽  
Total Water ◽  
Matric Potential ◽  
Thermocouple Psychrometer ◽  
Water Potentials

This study examined two polyethylene glycol (PEG) polymers (PEG 6000 and PEG 10000) and compared measurements of water potential obtained with a thermocouple osmometer and thermocouple psychrometers at three temperatures (15, 25 and 35�C) and five osmdalities (50, 100, 200, 300 and 400 g/1000 g water). These were then compared with estimates of matric potential of three soils brought to equilibrium with PEG solutions of the same osmolalities. At the same osmolality and temperature the two PEG polymers gave essentially the same water potential. There was a significant effect of temperature on water potential which corresponded closely with changes in specific gravity of the PEG solution. There was a close correlation between the measurements of water potential of the PEG solutions obtained with the osmometer and the psychrometers (R = 0.99). However, the psychrometer gave increasingly lower values than the osmometer as water potential decreased. The differences in the measurements between the two methods are thought to be the result of design and calibration differences. The ease of use of the osmometer is such that it is recommended for routine use. The water potentials of the soil cores brought to equilibrium with the PEG 10 000 solution were linearly related to the water potentials of the PEG solutions estimated from both the osmometer and psychrometers (R2 = 0.84). However, there were clear deviations from a 1:l relationship. It was concluded that the results from the soil cores could not be used to determine which of the two instruments gave the more accurate measurement of water potential of PEG solutions.

Evaluation of the hydraulic press for measurement of leaf water potentials in cassava

1983 ◽  
Vol 101 (2) ◽  
pp. 407-410 ◽  
Author(s):  
J. A. Palta
Keyword(s):  
Water Potential ◽  
Leaf Water Potential ◽  
Hydraulic Press ◽  
Pressure Chamber ◽  
Leaf Water ◽  
Moisture Loss ◽  
Total Leaf Area ◽  
Water Potentials ◽  
Wide Range ◽  
Poor Relationship

SUMMARYIn the application of the Scholander pressure chamber technique to cassava water relations studies, the leaf water potential measured on central lobules was initially compared with that measured on entire leaves (including petiole). Measurements made using both a Campbell-Brewster hydraulic press and a pressure chamber of the leaf water potential in six different cassava clones were also compared. Although the central lobules showed a greater sensitivity to moisture loss after sampling than entire leaves, their leaf water potential was in close agreement with those measured on the entire leaves (r3 = 0·96). Therefore, for routine and field estimates in cassava, measurements made on the central lobules may be used to avoid the large reduction in total leaf area. The Campbell-Brewster hydraulic press satisfactorily estimated leaf water potential in M.Col. 1684 clone, which had the longest and narrowest lobules, but in other clones the leaf water potential was overestimated at high leaf potential (> -12·5) and underestimated at low water potentials (< -12·5). Over a wide range of leaf water potentials, a poor relationship between leaf water potentials estimated with hydraulic press and with the pressure chamber was observed for cassava because press estimates are influenced by lobule length and lobule width.

Dehydration tolerance of five bur oak (Quercusmacrocarpa) seed sources from Texas, Nebraska, Minnesota, and New York

1993 ◽  
Vol 23 (3) ◽  
pp. 387-393 ◽  
Author(s):  
Michael R. Kuhns ◽  
Walter W. Stroup ◽  
G. Michael Gebre
Keyword(s):  
New York ◽  
Water Potential ◽  
Electrolyte Leakage ◽  
Dry Period ◽  
Membrane Injury ◽  
North Central ◽  
Dehydration Tolerance ◽  
Seed Sources ◽  
Water Potentials ◽  
Bur Oak

Dehydration tolerance was studied in saplings of five widely distributed sources of Quercusmacrocarpa Michx. growing together in an outdoor plot in Lincoln, Nebraska. Membrane electrolyte leakage, expressed as percent injury, was used as a measure of dehydration tolerance. Leaves were excised from several plants of each source on July 16 after a long dry period and on August 26 after a long moist period. Leaves were allowed to dry for various times in a laboratory, their water potential was measured, and membrane injury was determined. Regressions were calculated for percent injury versus leaf water potential, so sources could be compared at selected water potentials. All sources showed increased leakage at lower water potentials, with most leakage occurring below a water potential of −3 MPa. A source from Texas had the highest leakage, 23% at −6 MPa in August, while a source from a more xeric site in north central Nebraska generally had the lowest leakage. Stress preconditioning appeared to affect leakage, with leakage often significantly lower in July than in August.

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