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.

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.

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.

Lateral Earth Pressure Coefficient of Soils Subjected to Freeze–Thaw

2017 ◽  
Vol 140 (2) ◽  
Author(s):  
Xiaodong Zhao ◽  
Guoqing Zhou ◽  
Bo Wang ◽  
Wei Jiao ◽  
Jing Yu
Keyword(s):  
Pressure Coefficient ◽  
Earth Pressure ◽  
Retaining Walls ◽  
Saturated Soil ◽  
Frozen Soils ◽  
Freeze Thaw ◽  
Lateral Earth Pressure ◽  
Soil Deposits ◽  
Earth Pressure Coefficient ◽  
Water Saturated

Artificial frozen soils (AFS) have been used widely as temporary retaining walls in strata with soft and water-saturated soil deposits. After excavations, frozen soils thaw, and the lateral earth pressure penetrates through the soils subjected to freeze–thaw, and acts on man-made facilities. Therefore, it is important to investigate the lateral pressure (coefficient) responses of soils subjected to freeze–thaw to perform structure calculations and stability assessments of man-made facilities. A cubical testing apparatus was developed, and tests were performed on susceptible soils under conditions of freezing to a stable thermal gradient and then thawing with a uniform temperature (Fnonuni–Tuni). The experimental results indicated a lack of notable anisotropy for the maximum lateral preconsolidated pressures induced by the specimen’s compaction and freeze–thaw. However, the freeze–thaw led to a decrement of lateral earth pressure coefficient  K0, and  K0 decrement under the horizontal Fnonuni–Tuni was greater than that under the vertical Fnonuni–Tuni. The measured  K0 for normally consolidated and over-consolidated soil specimens exhibited anisotropic characteristics under the vertical Fnonuni–Tuni and horizontal Fnonuni–Tuni treatments. The anisotropies of  K0 under the horizontal Fnonuni–Tuni were greater than that under the vertical Fnonuni–Tuni, and the anisotropies were more noticeable in the unloading path than that in the loading path. These observations have potential significances to the economical and practical design of permanent retaining walls in soft and water-saturated soil deposits.

Heat Exchange Between a Tube and Water-Saturated Soil

1986 ◽  
Vol 108 (4) ◽  
pp. 298-302 ◽  
Author(s):  
C. A. van der Star ◽  
G. A. M. van Meurs ◽  
C. J. Hoogendoorn
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Thermal Properties ◽  
Saturated Soil ◽  
Mutual Distance ◽  
Tube Material ◽  
Surrounding Water ◽  
Analytical Approximations ◽  
Water Saturated ◽  
Regional Groundwater

The heat transfer between a cylinder and the surrounding water-saturated soil is studied numerically. Parameters which influence this heat transfer are thermal properties of the soil, dimension and thermal conductivity of the tube material, and a regional groundwater flow. The results are compared to analytical approximations. When two tubes are present, their mutual distance is also such a parameter.

scholarly journals Vertical Impedance of Rigid Shallow Foundation on Layered Water-Saturated Soil

2019 ◽  
pp. 165-167
Author(s):  
Oleksandr Trofymchuk ◽  
Oleh Savytskyi
Keyword(s):  
Numerical Analysis ◽  
Oscillation Frequency ◽  
Saturated Soil ◽  
Shallow Foundation ◽  
Mechanical Parameters ◽  
Lower Edge ◽  
Rigid Plate ◽  
Water Saturated ◽  
Impedance Functions ◽  
Biot’S Model

Methods have been developed for numerical analysis the vertical oscillations of rigid plate with a liquidimpermeable sole rested on the layer (Biot’s model) with a rigidly restrained lower edge. The plate sole is liquid-impermeable. The analysis of the impedance functions depending on the oscillation frequency, the geometry of the system and the mechanical parameters of the soil model is carried out.

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