Ballistospore discharge in Tilletiopsis minor

1973 ◽  
Vol 51 (3) ◽  
pp. 589-593 ◽  
Author(s):  
S. M. Pady
Keyword(s):  
Relative Humidity ◽  
Continuous Light ◽  
Endogenous Rhythm ◽  
Growth Chamber ◽  
Puccinia Malvacearum

Ballistospore discharge in Tilletiopsis minor Nyland was studied in a growth chamber under various conditions using a Kramer-Collins Spore Sampler. Sporulation occurred on leaves of Althea naturally infected with Puccinia malvacearum, on inoculated healthy leaves of Althea, and on 11 other hosts. Under alternating dark (12 h, 90–94% relative humidity (RH)) and light (12 h, 80% RH) at 21 °C, sporulation occurred periodically, only when humidity was high. There was no evidence of an endogenous rhythm in continuous light or dark.

The Effect of Surfactant and Environment on the Toxicity of Metriflufen to Soybeans (Glycine max) and Johnsongrass (Sorghum halepense)

Weed Science ◽  
1979 ◽  
Vol 27 (6) ◽  
pp. 675-679 ◽  
Author(s):  
C. G. McWhorter
Keyword(s):  
Glycine Max ◽  
Methyl Ester ◽  
Relative Humidity ◽  
Air Temperature ◽  
Sorghum Halepense ◽  
Growth Chamber ◽  
Propanoic Acid ◽  
Herbicide Treatment ◽  
Over The Top

Metriflufen {2-[4-(4-trifluoromethylphenoxy)phenoxy] propanoic acid} was applied as the methyl ester at 0.28 and 0.56 kg/ha over-the-top to johnsongrass [Sorghum halepense(L.) Pers.] growing from rhizomes and to soybeans [Glycine max(L.) Merr. ‘Lee 68′]. After herbicide treatment, plants were grown in the growth chamber for 14 days at 16, 24, or 32 C with relative humidity (RH) at 40 or 100% at each air temperature. Johnsongrass was not controlled at 16 C regardless of metriflufen rate, RH, or the addition of nonoxynol [α-(p-nonylphenyl)-ω-hydroxypoly (oxyethylene)] (with 9.5 moles of polyoxyethylene) surfactant at 0.25 (g/100 ml) to spray solutions. Johnsongrass control at 24 C varied from 5 to 98%, with significantly better control at 100% than at 40% RH. The presence of surfactant increased johnsongrass control at 24 C and 40% RH but not at 24 C and 100% RH. Johnsongrass control at 32 C varied from 48 to 98%, and it was not increased by the presence of the surfactant, regardless of metriflufen rate or RH level. At 16 C metriflufen was more injurious to soybeans than to johnsongrass, but at 24 and 32 C johnsongrass control was significantly greater than soybean injury. The presence of surfactant in spray solutions generally did not increase soybean injury, regardless of temperature or RH level. These results suggest that metriflufen is most selective in controlling johnsongrass in soybeans at 24 C, especially under high RH.

Root and Foliar Absorption of Atrazine Applied Postemergence to Broadleaf Weeds

Weed Science ◽  
1970 ◽  
Vol 18 (3) ◽  
pp. 349-351 ◽  
Author(s):  
Lafayette Thompson ◽  
F. W. Slife
Keyword(s):  
Relative Humidity ◽  
Field Experiments ◽  
Foliar Spray ◽  
High Relative Humidity ◽  
Growth Chamber ◽  
Foliar Absorption ◽  
Root Absorption

Results from both growth chamber and field experiments indicate that root absorption of 2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine (atrazine) applied postemergence to small broadleaf weeds is not a requisite for their control. Though broadleaf weeds absorb toxic quantities of atrazine from wet soil, they can be killed by foliar absorption alone because all of their meristems are exposed to a foliar spray. They are particularly sensitive when foliar penetration is enhanced by high relative humidity and wet foliage.

Temperature and Relative Humidity Effects on Diphenylether Herbicides

1992 ◽  
Vol 6 (1) ◽  
pp. 19-24 ◽  
Author(s):  
Rex A. Wichert ◽  
Robert Bozsa ◽  
Ronald E. Talbert ◽  
Lawrence R. Oliver
Keyword(s):  
Relative Humidity ◽  
Herbicidal Activity ◽  
High Relative Humidity ◽  
Growth Chamber ◽  
Similar Response ◽  
Application Timing ◽  
Influence Of Temperature ◽  
Humidity Effects ◽  
Lower Temperature ◽  
Prickly Sida

The influence of temperature and relative humidity on the activity of acifluorfen, fomesafen, lactofen, and acifluorfen plus bentazon on prickly sida, pitted and entireleaf morningglory, and common cocklebur was evaluated in a growth chamber. Reduced control of all species was observed at 50% relative humidity as compared to 85% relative humidity when temperatures were higher (32/55 C day/night). Similar response to relative humidity was observed at the lower temperature (25/15 C) when treatments were applied 14 days after emergence (DAE). Changes in temperature at the same relative humidity did not alter herbicidal activity. Delaying application timing from 7 to 14 DAE decreased control by all herbicides except lactofen applied at high relative humidity, which controlled prickly sida at both 7 and 14 DAE.

Factors that Influence Germination and Mycoherbicidal Activity ofAlternaria cassiae

1991 ◽  
Vol 5 (1) ◽  
pp. 82-86 ◽  
Author(s):  
Donald J. Daigle ◽  
Peter J. Cotty
Keyword(s):  
Relative Humidity ◽  
Phosphate Buffer ◽  
Potassium Phosphate ◽  
Tween 80 ◽  
Growth Chamber ◽  
Potassium Phosphate Buffer ◽  
Potato Dextrose Broth ◽  
Leaf Stage ◽  
True Leaf

The influences of pH, surfactants, and nutrients on germination were investigated to develop a basis for improvement ofAlternaria cassiaemycoherbicide formulations. In vitro results indicated that a formulation with a pH of approximately 6.5 containing 0.1 to 1% Tween 80, 0.02 M potassium phosphate buffer, and 1% dehydrated potato dextrose broth best promoted germination. Sicklepod plants at the 2 to 3 true-leaf stage were sprayed with test solutions, incubated in the dark at 100% relative humidity (28 C) for 6 h, and placed in a growth chamber maintained at 30 C. Assessment of the plants after 2 d indicated that the ability of the formulation components to induce germination ofAlternaria cassiaein vitro corresponded well with their ability to improve infection of sicklepod seedlings.

Effect of humidity and light periods on infection and sporulation of Peronospora viciae on Pisum sativum

1981 ◽  
Vol 59 (12) ◽  
pp. 2515-2518
Author(s):  
H. Singh
Keyword(s):  
Relative Humidity ◽  
Pisum Sativum ◽  
Dark Period ◽  
Continuous Light ◽  
High Relative Humidity ◽  
High Humidity ◽  
Peronospora Viciae

Plants grown in high relative humidity (RH > 90%) before inoculation supported more sporulation than those kept in drier (RH < 30%) conditions. Sporulation of Peronospora viciae (Berk.) Casp. on Pisum sativum (Berk.) Casp. cv. Superb was lower on plants kept under continuous light for 2 weeks before inoculation than on those maintained in a 12 h light: 12 h dark photoperiod. Treatments involving longer photoperiods after inoculation resulted in greater sporulation (intensity) than those where inoculation was followed by an extended dark period. A minimum of 6 h of high humidity (RH > 90%) in the dark was required to initiate sporulation. However, this period was reduced to 3 h if replaced by lower humidity conditions (RH 65%).

scholarly journals The triple oxygen isotope composition of phytoliths, a new proxy of atmospheric relative humidity: controls of soil water isotope composition, temperature, CO<sub>2</sub> concentration and relative humidity

2021 ◽  
Author(s):  
Clément Outrequin ◽  
Anne Alexandre ◽  
Christine Vallet-Coulomb ◽  
Clément Piel ◽  
Sébastien Devidal ◽  
...  
Keyword(s):  
Relative Humidity ◽  
Oxygen Isotope ◽  
Soil Water ◽  
Isotope Composition ◽  
Co2 Concentration ◽  
Oxygen Isotope Composition ◽  
Growth Chamber ◽  
Starting Point ◽  
Atmospheric Relative Humidity ◽  
Water Isotope

Abstract. Continental atmospheric relative humidity is a major climate parameter whose variability is poorly understood by global climate models. Models’improvement relies on model-data comparisons for past periods. However, there are no truly quantitative indicators of relative humidity for the pre-instrumental period. Previous studies highlighted a quantitative relationship between the triple oxygen isotope composition of phytoliths, and particularly the 17O-excess of phytoliths, and atmospheric relative humidity. Here, as part of a series of calibrations, we examine the respective controls of soil water isotope composition, temperature, CO2 concentration and relative humidity on phytolith 17O-excess. For that purpose, the grass species Festuca arundinacea was grown in growth chambers where these parameters were varying. The setup was designed to control the evolution of the triple oxygen isotope composition of phytoliths and all the water compartments of the soil-plant-atmosphere continuum. Different analytical techniques (cavity ring-down spectroscopy and isotope ratio mass spectrometry) were used to analyse water and silica. An inter-laboratory comparison allowed to strengthen the isotope data matching. Water and phytolith isotope compositions were compared to previous datasets obtained from growth chamber and natural tropical sites. The results show that the δ'18O value of the source water governs the starting point from which the triple oxygen isotope composition of leaf water, phytolith-forming water and phytoliths evolve. However, since the 17O-excess varies little in the growth chamber and natural source waters, this has no impact on the strong relative humidity-dependency of the 17O-excess of phytoliths, demonstrated for the 40–80 % relative humidity range. This relative humidity-dependency is not impacted by changes in air temperature or CO2 concentration either. A relative humidity proxy equation is proposed. Each per meg of change in phytolith 17O-excess reflects a change in atmospheric relative humidity of ca. 0.2 %. The ±15 per meg reproducibility on the measurement of phytolith 17O-excess corresponds to a ± 3.6 % precision on the reconstructed relative humidity. The low sensitivity of phytolith 17O-excess to climate parameters other than relative humidity makes it particularly suitable for quantitative reconstructions of continental relative humidity changes in the past.

scholarly journals Glyphosate Efficacy on Velvetleaf Varies with Application Time of Day

2004 ◽  
Vol 18 (4) ◽  
pp. 931-939 ◽  
Author(s):  
Aaron L. Waltz ◽  
Alex R. Martin ◽  
Fred W. Roeth ◽  
John L. Lindquist
Keyword(s):  
Relative Humidity ◽  
Air Temperature ◽  
Leaf Blade ◽  
Time Of Day ◽  
Growth Chamber ◽  
Natural Light ◽  
Horizontal Position ◽  
Application Time ◽  
Orientation Growth

Field and growth chamber experiments determined the efficacy of temporal glyphosate applications on velvetleaf. Glyphosate was applied postemergence to velvetleaf periodically before and during light and after dark. In 1999, glyphosate at 840 g ae/ha applied before sunrise and after midday provided 54 and 100% velvetleaf control, respectively. In 2000, glyphosate at 840 g/ha applied before sunrise, midday, and after sunset provided 69, 100, and 37% velvetleaf control, respectively. In the growth chamber, glyphosate at 840 g/ha applied before or after light reduced velvetleaf biomass 15 to 20% or 32 to 47%, respectively, and reduced velvetleaf height 24% or 45 to 54%, respectively. Velvetleaf control was consistently greater with glyphosate applications during light compared with dark, regardless of constant air temperature and relative humidity (growth chamber), dew absence or presence (field and growth chamber), or leaf blade orientation (growth chamber) with natural light–dark movements or a fixed horizontal position.

Effect of Environment on the Translocation and Toxicity of Acifluorfen to Showy Crotalaria (Crotalaria spectabilis)

Weed Science ◽  
1981 ◽  
Vol 29 (4) ◽  
pp. 397-401 ◽  
Author(s):  
Gene D. Wills ◽  
Chester G. McWhorter
Keyword(s):  
Relative Humidity ◽  
Growth Chamber ◽  
Nitrobenzoic Acid ◽  
Single Leaf ◽  
Air Temperatures ◽  
Over The Top ◽  
Crotalaria Spectabilis

Toxicity of non-radiolabeled and absorption and translocation of14C-activity of applied14C-acifluorfen {5-[2-chloro-4-(trifluoromethyl)phenoxy]-2-nitrobenzoic acid} in showy crotalaria (Crotalaria spectabilisRoth) were evaluated in the growth chamber at air temperatures of 18, 27, or 35 C and 40 or 100% relative humidity (RH). Four days after treatment, acifluorfen applied over-the-top at 0.1 kg/ha resulted in 64 to 95% injury, but did not kill showy crotalaria. Acifluorfen was more toxic at 100% than at 40% RH. At either 40 or 100% RH, acifluorfen was more toxic at 27 and 35 C than at 18 C. Plants were placed in the greenhouse 4 days after treatment. At 6 weeks after treatment, there was extensive regrowth, and injury to all plants was less than 32%, except for those plants initially treated at 18 C and 40% RH for 4 days. These plants showed 76% injury. Acifluorfen applied to a single leaf midway up the stem caused 80 to 100% injury to the immature leaves near the apex, but less than 30% injury to lower leaves. Absorption of14C-activity from14C-acifluorfen applied to a single leaf midway up the shoot varied from 8 to 76% after 2 days. At either 40 or 100% RH, absorption was approximately four-fold greater at 27 and 35 C than at 18 C. At all temperatures tested, absorption was three- to four-fold greater at 100% than at 40% RH.

scholarly journals The triple oxygen isotope composition of phytoliths, a new proxy of atmospheric relative humidity: controls of soil water isotope composition, temperature, CO<sub>2</sub> concentration and relative humidity

2021 ◽  
Vol 17 (5) ◽  
pp. 1881-1902
Author(s):  
Clément Outrequin ◽  
Anne Alexandre ◽  
Christine Vallet-Coulomb ◽  
Clément Piel ◽  
Sébastien Devidal ◽  
...  
Keyword(s):  
Relative Humidity ◽  
Oxygen Isotope ◽  
Soil Water ◽  
Isotope Composition ◽  
Co2 Concentration ◽  
Oxygen Isotope Composition ◽  
Growth Chamber ◽  
Starting Point ◽  
Atmospheric Relative Humidity ◽  
Water Isotope

Abstract. Continental atmospheric relative humidity is a major climate parameter whose variability is poorly understood by global climate models. Models' improvement relies on model–data comparisons for past periods. However, there are no truly quantitative indicators of relative humidity for the pre-instrumental period. Previous studies highlighted a quantitative relationship between the triple oxygen isotope composition of phytoliths, particularly the 17O excess of phytoliths, and atmospheric relative humidity. Here, as part of a series of calibrations, we examine the respective controls of soil water isotope composition, temperature, CO2 concentration and relative humidity on phytolith 17O excess. For that purpose, the grass species Festuca arundinacea was grown in growth chambers where these parameters were varying. The setup was designed to control the evolution of the triple oxygen isotope composition of phytoliths and all the water compartments of the soil–plant–atmosphere continuum. Different analytical techniques (cavity ring-down spectroscopy and isotope ratio mass spectrometry) were used to analyze water and silica. An inter-laboratory comparison allowed to strengthen the isotope data matching. Water and phytolith isotope compositions were compared to previous datasets obtained from growth chamber and natural tropical sites. The results show that the δ′18O value of the source water governs the starting point from which the triple oxygen isotope composition of leaf water, phytolith-forming water and phytoliths evolves. However, since the 17O excess varies little in the growth chamber and natural source waters, this has no impact on the strong relative humidity dependency of the 17O excess of phytoliths, demonstrated for the 40 %–80% relative humidity range. This relative humidity dependency is not impacted by changes in air temperature or CO2 concentration either. A relative humidity proxy equation is proposed. Each per meg of change in phytolith 17O excess reflects a change in atmospheric relative humidity of ca. 0.2 %. The ±15 per meg reproducibility on the measurement of phytolith 17O excess corresponds to a ±3.6 % precision on the reconstructed relative humidity. The low sensitivity of phytolith 17O excess to climate parameters other than relative humidity makes it particularly suitable for quantitative reconstructions of continental relative humidity changes in the past.

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