Embryo dormancy responses to temperature in capeweed (Arctotheca calendula) seeds

2002 ◽  
Vol 12 (3) ◽  
pp. 181-191 ◽  
Author(s):  
Amanda J. Ellery
Keyword(s):  
Soil Temperature ◽  
Water Potential ◽  
Low Temperatures ◽  
Seasonal Changes ◽  
Temperature Fluctuation ◽  
Soil Surface ◽  
Seed Collection ◽  
Embryo Dormancy ◽  
Response To Temperature ◽  
Dormancy Cycles

Changes in embryo dormancy of capeweed [Arctotheca calendula (L.) Levyns.] seeds in response to temperature were investigated to determine the nature of seasonal dormancy cycles. Primary embryo dormancy persisted for 2–3 months after seed collection and was then rapidly relieved when seeds were maintained at temperatures simulating summer soil surface temperatures. Embryo dormancy was also rapidly relieved in seeds maintained at constant temperatures, indicating that a daily temperature fluctuation was not necessary for the relief of embryo dormancy in capeweed. Dormancy relief was maximal at 40°C. Secondary dormancy was induced when seeds were maintained at low temperatures and a water potential of –1.5 MPa, suggesting that the onset of winter may postpone germination until a subsequent autumn. These results indicate that the dormancy cycles observed in capeweed seeds maintained on the soil surface are probably driven by seasonal changes in soil temperature.

EVALUATION OF CRITERIA FOR THE CLASSIFICATION OF GLEYSOLIC SOILS IN SASKATCHEWAN

1989 ◽  
Vol 69 (1) ◽  
pp. 153-164 ◽  
Author(s):  
J. J. MILLER ◽  
D. F. ACTON ◽  
R. J. ST. ARNAUD
Keyword(s):  
Soil Temperature ◽  
Water Table ◽  
Seasonal Changes ◽  
Soil Surface ◽  
Redox Status ◽  
Hydrophytic Vegetation ◽  
Soil Zone ◽  
Morphological Criteria ◽  
Lower Slope

Six soils within and adjacent to two willow-ring depressions in hummocky moraine of the Dark Brown soil zone were monitored for seasonal changes in water table levels, redox status, and soil temperature to evaluate color citeria for identifying saturated and reduced soils of the Gleysolic order. Soils in the center of the willow-ring depressions had water table levels close to the soil surface, Ept values of < 100 mV, and were covered by hydrophytic vegetation. Soils near the perimeter of the willow-ring depression had water table levels generally below 1 m, Ept values > 400 mV, and were covered by hydrophytic vegetation. Three of the depressional soils had matrix chromas of 1 in the Ae and/or Bt (Btj) horizons, with prominent rusty mottles, and met the color criteria of Humic Luvic Gleysols. The fourth depressional soil had matrix chromas of 1 in the Btj horizon, but no mottles were present within 50 cm of the soil surface, and met the color criteria of an Orthic Humic Gleysol. Two nondepressional soils, on lower slope positions just outside the willow-ring depressions, exhibited water table levels generally below 1.5 m, had an Ept of > 400 mV, and lacked hydrophytic vegetation. Of these, one soil had matrix chromas of 2 and prominent rusty mottles within 50 cm of the soil surface and met the color criteria of a Rego Humic Gleysol. The other had mottles of low chroma within 1 m of the surface and met the color criteria of a Gleyed Rego Dark Brown. Based on this study, the color criteria are adequate for depressional soils but are inadequate for the classification of soils beyond the willow-ring. Key words: Water table level, redox potential, soil temperature, morphological criteria, gleying

Analytical Model to Predict Nonhomogeneous Soil Temperature Variation

1995 ◽  
Vol 117 (2) ◽  
pp. 100-107 ◽  
Author(s):  
M. Krarti ◽  
D. E. Claridge ◽  
J. F. Kreider
Keyword(s):  
Thermal Properties ◽  
Soil Temperature ◽  
Temperature Variation ◽  
Analytical Model ◽  
Soil Surface ◽  
Deep Soil ◽  
Soil Thermal Properties ◽  
Order Of Magnitude ◽  
Soil Surface Temperature ◽  
Annual Time

This paper presents an analytical model to predict the temperature variation within a multilayered soil. The soil surface temperature is assumed to have a sinusoidal time variation for both daily and annual time scales. The soil thermal properties in each layer are assumed to be uniform. The model is applied to two-layered, three-layered, and to nonhomogeneous soils. In case of two-layered soil, a detailed analysis of the thermal behavior of each layer is presented. It was found that as long as the order of magnitude of the thermal diffusivity of soil surface does not exceed three times that of deep soil; the soil temperature variation with depth can be predicted accurately by a simplified model that assumes that the soil has constant thermal properties.

scholarly journals A field perspective on effects of fire and temperature fluctuation on Cerrado legume seeds

2017 ◽  
Vol 27 (2) ◽  
pp. 74-83 ◽  
Author(s):  
L. Felipe Daibes ◽  
Talita Zupo ◽  
Fernando A.O. Silveira ◽  
Alessandra Fidelis
Keyword(s):  
Temperature Fluctuation ◽  
Field Experiments ◽  
Seed Viability ◽  
Soil Surface ◽  
Temperature Fluctuations ◽  
Fire Effects ◽  
Fuel Load ◽  
Physical Dormancy ◽  
Legume Seeds ◽  
Field Perspective

AbstractInformation from a field perspective on temperature thresholds related to physical dormancy (PY) alleviation and seed resistance to high temperatures of fire is crucial to disentangle fire- and non-fire-related germination cues. We investigated seed germination and survival of four leguminous species from a frequently burned open Neotropical savanna in Central Brazil. Three field experiments were conducted according to seed location in/on the soil: (1) fire effects on exposed seeds; (2) fire effects on buried seeds; and (3) effects of temperature fluctuations on exposed seeds in gaps and shaded microsites in vegetation. After field treatments, seeds were tested for germination in the laboratory, together with the control (non-treated seeds). Fire effects on exposed seeds decreased viability in all species. However, germination of buried Mimosa leiocephala seeds was enhanced by fire in an increased fuel load treatment, in which we doubled the amount of above-ground biomass. Germination of two species (M. leiocephala and Harpalyce brasiliana) was enhanced with temperature fluctuation in gaps, but this condition also decreased seed viability. Our main conclusions are: (1) most seeds died when exposed directly to fire; (2) PY could be alleviated during hotter fires when seeds were buried in the soil; and (3) daily temperature fluctuations in gaps also broke PY of seeds on the soil surface, so many seeds could be recruited or die before being incorporated into the soil seed banks. Thus seed dormancy-break and germination of legumes from Cerrado open savannas seem to be driven by both fire and temperature fluctuations.

Corrigendum - Growth of potatoes (Solanum tuberosum L.) to the small tuber stage as related to soil temperature

1979 ◽  
Vol 30 (4) ◽  
pp. 667
Author(s):  
PJM Sale
Keyword(s):  
Soil Temperature ◽  
Low Temperatures ◽  
Solanum Tuberosum L ◽  
Tuber Initiation ◽  
Degree Days ◽  
Night Temperature ◽  
Field Development ◽  
Periodic Fluctuations ◽  
The Times ◽  
The Relationship

In experiments in a phytotron with potato cv. Sebago and in the field with cvv. Sebago and Sequoia the times for planting to emergence, new tuber initiation and small tuber stage were measured in relation to temperature. Emergence was linearly related to mean temperature and relatively independent of diurnal or periodic fluctuations up to an optimum of 22–24°C, and up to this optimum could be considered as a degree-day requirement calculated from either soil temperature at tuber depth or air temperature. For both cultivars planted with just-visible sprouts this was about 450 degree-days reckoned above a +2° minimum. At temperatures above the optimum, emergence was actively inhibited, and the relationship no longer held when appreciable periods were spent above about 24°. Once emergence had occurred, new tuber initiation and growth to the small tuber stage tended to be promoted at low temperatures especially in cv. Sequoia; phytotron treatments where night temperature was higher than day had a particularly adverse effect. It appeared that field development was adversely affected if a rapid increase in soil temperature occurred during the period of emergence.

Drainage and evaporation from fallow soil at Rothamsted

1941 ◽  
Vol 31 (1) ◽  
pp. 74-109 ◽  
Author(s):  
H. L. Penman ◽  
R. K. Schofield
Keyword(s):  
Soil Temperature ◽  
Seasonal Change ◽  
Seasonal Changes ◽  
Pore Space ◽  
Marked Change ◽  
Field Capacity ◽  
Measurable Effect ◽  
Average Value ◽  
Fallow Soil ◽  
Viscosity Changes

1. Study of the automatic records shows:(a) There is a seasonal change in the drainage response after rain which can be almost wholly ascribed to viscosity changes arising from seasonal changes of soil temperature (p. 77).(b) Evaporation occurring after a fall of rain has no measurable effect on the drainage response to that rain (pp. 78, 87).(c) The maximum drainage rates for the 20 in. gauge are much larger than those for the deeper gauges. The maxima change seasonally and are again primarily dependent on viscosity (p. 78).(d) There is no marked change in the field capacity of the gauge during the year. The air-filled pore space at field capacity may change by about 15% of its average value (p. 81).

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