scholarly journals Quantifying cardinal temperatures and thermal time required for germination of Silybum marianum seed

2015 ◽  
Vol 3 (2) ◽  
pp. 145-151 ◽  
Author(s):  
Ghasem Parmoon ◽  
Seyed Amir Moosavi ◽  
Hamed Akbari ◽  
Ali Ebadi
Keyword(s):  
Thermal Time ◽  
Silybum Marianum ◽  
Time Required ◽  
Cardinal Temperatures

Cardinal temperatures and thermal time required foremergence of lenti (Lens culinaris Medik)

2017 ◽  
Author(s):  
Ali reza Safahani ◽  
Behnam Kamakar ◽  
Amir Nabizadeh
Keyword(s):  
Lens Culinaris ◽  
Seedling Emergence ◽  
Information Criterion ◽  
Optimization Method ◽  
Thermal Time ◽  
Coefficient Of Determination ◽  
Nonlinear Regression Models ◽  
Maximum Temperatures ◽  
Time Required ◽  
Cardinal Temperatures

The present study was performed to compare four nonlinear regression models (segmented, beta, beta modified, and dent-like) to describe the emergence rate–temperature relationships of six lentil (Lens culinaris Medik) cultivars at field experiment with a range of sowing dates, with the aim of identifying the cardinal temperatures and physiological days (i.e., number of days under optimum temperatures) required for seedling emergence. Models and statistical indices were calibrated using an iterative optimization method and their performance was compared by root mean square error (RMSD), coefficient of determination (R2) and corrected Akaike information criterion correction (AIC). The beta model was found to be the best model for predicting the response of lentil emergence to temperature, (R2= 0.99; RMSD= 0.005; AICc= -232.97). Based on the model outputs, the base, optimum, and maximum temperatures of seedling emergence were 4.5, 22.9, and 40 °C, respectively. The Six physiological days (equivalent to a thermal time of 94 °C days) were required from sowing to emergence

A quantitative analysis of dormancy loss dynamics inPolygonum aviculareL. seeds: Development of a thermal time model based on changes in seed population thermal parameters

2003 ◽  
Vol 13 (1) ◽  
pp. 55-68 ◽  
Author(s):  
Diego Batlla ◽  
Roberto Luis Benech-Arnold
Keyword(s):  
Time Course ◽  
Model Performance ◽  
Thermal Parameters ◽  
Thermal Time ◽  
Threshold Temperature ◽  
Time Model ◽  
Germination Time ◽  
Polygonum Aviculare ◽  
Seed Population ◽  
Time Required

AbstractA model for simulatingPolygonum aviculareL. seed dormancy loss in relation to stratification temperature was developed. The model employs the lower limit temperature for germination (Tl) as an index of seed population dormancy status. While population mean forTl(Tl(50)) andTldistribution within the population (σTl) are allowed to vary as seeds are released from dormancy, other thermal parameters characterizing the germination thermal responses (base, optimal and maximal temperatures, and thermal time required for germination) and the higher limit temperature for germination (Th) are held constant. In order to relate changes inTl(50)and σTlto variable time and temperature, a stratification thermal time index (Stt) was developed, which consists of the accumulation of thermal time units under a threshold temperature for dormancy loss to occur. Therefore,Tl(50)and σTlvaried in relation to the accumulation ofSttaccording to time and temperature. To derive model equations, changes in seed population thermal parameters were estimated for buried seeds stored at 1.6, 7 and 12°C for 110 d. Seeds were exhumed at regular intervals, and were incubated at 15°C and at a gradually increasing temperature regime in the range 6–25°C. The germination time-course curves obtained were reproduced using a mathematical model. Thermal parameters that best fit simulated and experimentally obtained germination time-course curves were determined. Model performance was evaluated against data of two unrelated experiments, showing acceptable prediction of timing and percentage of germination of seeds exhumed from field and controlled temperature conditions.

Effects of Temperature, Soil Water Status and Depth of Planting on Germination and Emergence of Maize (Zea Mays) Adapted to Semi-Arid Eastern Kenya

1993 ◽  
Vol 29 (3) ◽  
pp. 351-364 ◽  
Author(s):  
J. K. Itabari ◽  
P. J. Gregory ◽  
R. K. Jones
Keyword(s):  
Water Content ◽  
Soil Water ◽  
Water Status ◽  
Soil Water Potential ◽  
Thermal Time ◽  
Controlled Environment ◽  
Base Temperature ◽  
Matric Potential ◽  
Effects Of Temperature ◽  
Time Required

SUMMARYThe effects of temperature and soil water potential on maize germination were investigated in controlled environment conditions and the effects of depth of planting and a mulch on maize emergence were studied in a field experiment in eastern Kenya. The rate of germination increased to an optimum temperature of 33.6°C above a base temperature of 6.1°C and decreased above the optimum to zero germination at 42.9°C. The thermal time for median germination increased from 51.5°Cd to 56.4°Cd as soil matric potential decreased from -5 to -40 kPa. Soil water content, depth of planting, and their interaction had significant (P < 0.001) effects on final germination and emergence but mulch, or any interactions involving mulch, had no such effects. Increasing depth of planting by 1 cm increased the thermal time required for emergence by 2.8°Cd, and decreasing water content by 1% increased the thermal time required for emergence by 3.2°Cd.Germinación y emergencia del maíz

scholarly journals Vernalization Responses of Campanula ‘Birch Hybrid’

2009 ◽  
Vol 134 (5) ◽  
pp. 497-504 ◽  
Author(s):  
Sonali R. Padhye ◽  
Arthur C. Cameron
Keyword(s):  
Flowering Time ◽  
Thermal Time ◽  
Vernalization Requirement ◽  
Flowering Response ◽  
Flower Time ◽  
Cardinal Temperatures

The objective of this study was to characterize the influence of vernalizing temperatures and durations based on different flowering responses of Campanula ‘Birch Hybrid’. Clonally propagated plants of Campanula ‘Birch Hybrid’ were exposed to −2.5, 0, 2.5, 5, 7.5, 10, 12.5, 15, 17.5, or 20 °C for 0, 3, 5, 7, 9, or 12 weeks and were subsequently grown at 20 °C in a greenhouse. Campanula ‘Birch Hybrid’ exhibited a near-obligate vernalization requirement, and all flowering responses studied were influenced by the treatment temperatures, durations, and their interactions. The minimum and maximum cardinal temperatures for vernalization were <0 °C and between 15 and 17.5 °C, respectively. The range of optimal vernalizing temperatures (Topt) varied based on the flowering response assessed. For instance, Topt for flowering percentage ranged between 2.5 to 7.5 °C, while Topt for number of open flowers was 0 to 12.5 °C when plants were vernalized for 5 weeks. Topt for flowering time also varied when analyzed as rate to flower, time to flower from the end of temperature treatments, total time to flower measured from the start of temperature treatments, and thermal time to flower. For example, after 12 weeks of treatment, Topt for thermal time to flower was 0 to 2.5 °C yet shifted to 2.5 to 12.5 °C for total time to flower. Because the flowering response being assessed altered the Topt, this study reiterates the significance of considering all relevant flowering responses while developing and interpreting vernalization models.

Evaluation of dormancy and germination responses to temperature inCarduus acanthoides and Anagallis arvensisusing a screening system, and relationship with field-observed emergence patterns

2000 ◽  
Vol 10 (1) ◽  
pp. 77-88 ◽  
Author(s):  
Betina C. Kruk ◽  
Roberto L. Benech-Arnold
Keyword(s):  
Prolonged Exposure ◽  
Seasonal Pattern ◽  
Thermal Conditions ◽  
Thermal Time ◽  
Base Temperature ◽  
Dormancy Release ◽  
Carduus Acanthoides ◽  
Thermal Range ◽  
Dry Storage ◽  
Time Required

AbstractExperiments on the facultative winter annuals Carduus acanthoides and Anagallis arvensis were performed: (i) to determine thermal conditions that induce or release dormancy, (ii) to investigate to what extent changes in dormancy level resulting from those thermal conditions explain the seasonal pattern of emergence of these species, and (iii) to estimate required thermal time and base temperature for the germination of non-dormant seeds. Carduus acanthoides required high temperatures followed by decreasing temperatures for dormancy release; however, low winter temperatures did not induce secondary dormancy as expected for a winter annual. To the contrary, low temperatures stimulated dormancy release in the long term. InA. arvensis, dormancy relief was enhanced by dry storage at 25°C, and the response to low temperature was different depending on moisture conditions. Prolonged exposure to moist-chilling increased the dormancy level of the population, while dry storage at 4°C relieved dormancy. For both species, changes in the thermal range permissive for germination as a result of dormancy modifications explained to a large extent the timing of the emergence periods observed in the field. In neither species did base temperature for germination change with the dormancy level of the population. Thermal time required forgermination ofC. acanthoidesvaried with dormancy, while forA. arvensisseeds it was constant.

scholarly journals Cardinal Temperatures and Thermal Time for Seed Germination of Brunonia australis (Goodeniaceae) and Calandrinia sp. (Portulacaceae)

HortScience ◽  
2011 ◽  
Vol 46 (5) ◽  
pp. 753-758 ◽  
Author(s):  
Robyn L. Cave ◽  
Colin J. Birch ◽  
Graeme L. Hammer ◽  
John E. Erwin ◽  
Margaret E. Johnston
Keyword(s):  
Seed Germination ◽  
Cumulative Distribution Function ◽  
Thermal Time ◽  
Cumulative Distribution ◽  
Maximum Temperature ◽  
Base Temperature ◽  
Percentage Germination ◽  
Maximum Temperatures ◽  
Seed Propagation ◽  
Cardinal Temperatures

Seed germination of Brunonia australis Sm. ex R.Br. and Calandrinia sp. (Mt. Clere: not yet fully classified) was investigated using a thermogradient plate set at different constant temperatures to determine seed propagation requirements of these potential floriculture species. Germination responses were tested at 3, 7, 11, 15, 18, 22, 25, 29, 34, and 38 °C. Germination data were modeled using the cumulative distribution function of the inverse normal, which provides information on lag, rate, and maximum seed germination for each temperature regime. To determine cardinal temperatures, the reciprocal time to median germination (1/t50) and percentage germination per day were calculated and regressed against temperature. Base temperature estimates for B. australis were 4.9 and 5.5 °C and optimum temperatures were 21.4 and 21.9 °C, whereas maximum temperatures were 35.9 and 103.5 °C, with the latter being clearly overestimated using the 1/t50 index. Base temperatures for Calandrinia sp. were 5.8 and 7.9 °C, whereas optimum and maximum temperature estimates of 22.5 and 42.7 °C, respectively, were reported using the percentage germination per day index. Maximum seed germination of 0.8 to 0.9, expressed as the probability of a seed germinating, occurred at 11 to 25 °C for B. australis, whereas maximum germination for Calandrinia sp. was 0.5 to 0.7 at 18 to 25 °C. Thermal time, the accumulation of daily mean temperate above a base temperature, was calculated for different germination percentages. Estimates of thermal time (°Cd) for 50% seed germination were 54 and 90 °Cd for B. australis and Calandrinia sp., respectively.

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