Time, Temperature and Germination of Pearl Millet (<i>Pennisetum typhoides</i>S. &amp; H.)

Garcia-Huidobro, J.; Monteith, J. L.; Squire, G. R.

doi:10.1093/jxb/33.2.297

Cited by 122 publications

(54 citation statements)

References 11 publications

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“…1/t 50 for 50% germination) generally increase linearly between the minimum or base temperature (T b ) and the optimum temperature (T o ), as in the degree-days or thermal time model, θ T (g) = (T -T b ) t g , where θ T (g) is the thermal time required from imbibition until radicle emergence of fraction or percentage g and T is the temperature at which the seeds are imbibed. The thermal time model has been applied extensively to describe seed germination timing in response to temperature (Bierhuizen and Wagenvoort, 1974;Garcia-Huidobro et al, 1982;Covell et al, 1986;Dahal et al, 1990;Alvarado and Bradford, 2002). Since all seeds in a population do not germinate simultaneously, germination rates of seed populations (rather than of specific percentages) can be analysed by transforming the cumulative germination percentages to probits and plotting versus a log time scale (Covell et al, 1986;Dahal et al, 1990).…”

Section: Germination and Respiration Responses To Temperature (Thermamentioning

confidence: 99%

Single-seed oxygen consumption measurements and population-based threshold models link respiration and germination rates under diverse conditions

Bello

Bradford

2016

Seed Sci. Res.

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Seed germination is responsive to diverse environmental, hormonal and chemical signals. Germination rates (i.e. speed and distribution in time) reveal information about timing, uniformity and extent of germination in seed populations and are sensitive indicators of seed vigour and stress tolerance. Population-based threshold (PBT) models have been applied to describe germination responses to temperature, water potential, hormones, ageing and oxygen. However, obtaining detailed data on germination rates of seed populations requires repeated observations at frequent times to construct germination time courses, which is labour intensive and often impractical. Recently, instruments have been developed to measure repeatedly the respiration (oxygen consumption) of individual seeds following imbibition, providing complete respiratory time courses for populations of individual seeds in an automated manner. In this study, we demonstrate a new approach that enables the use of single-seed respiratory data, rather than germination data, to characterize the responses of seed populations to diverse conditions. We applied PBT models to single-seed respiratory data and compared the results to similar analyses of germination time courses. We found consistent and quantitatively comparable relationships between seed respiratory and germination patterns in response to temperature, water potential, abscisic acid, gibberellin, respiratory inhibitors, ageing and priming. This close correspondence between seed respiration and germination time courses enables the use of semi-automated respiratory measurements to assess seed vigour and quality parameters. It also raises intriguing questions about the fundamental relationship between the respiratory capacities of seeds and the rates at which they proceed toward completion of germination.

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Section: Germination and Respiration Responses To Temperature (Thermamentioning

confidence: 99%

Single-seed oxygen consumption measurements and population-based threshold models link respiration and germination rates under diverse conditions

Bello

Bradford

2016

Seed Sci. Res.

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“…The modelling approach was based on concepts developed by Garcia-Huidobro et al (1982) and Gummerson (1986). They proposed that the rate of germination of each fraction (G) of the population is linearly related to suboptimal temperatures (T) and that the intercept on the temperature axis defines the base temperature (T b ) below which germination ceases.…”

Section: Models For Rate Of Germinationmentioning

confidence: 99%

“…In a similar study of the applicability of hydrothermal time to weed species (Kebreab & Murdoch, 1999), the problem of reduced germination outside optimum conditions was alleviated by the exposure of seeds of Orobanche aegyptiaca to a naturally present germination stimulant produced by the roots of the host plant. Gummerson (1986) and Garcia-Huidobro et al (1982) recommended plotting deciles to study the distribution of temperature and water potential bases within the whole seed population. Whereas the temperature bases are thought to be relatively constant (Dahal et al, 1990), water potential bases vary between seeds and are frequently quoted as a measure of the variation of germination rates within a population (Bradford, 1995).…”

Section: Implications Of Temperature Thresholdsmentioning

confidence: 99%

Modelling the germination of Stellaria media using the concept of hydrothermal time

Grundy¹,

Phelps²,

Reader³

et al. 2000

New Phytologist

122

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The germination characteristics of Stellaria media (common chickweed) were investigated over a range of constant temperatures and degrees of moisture stress in order to assess the suitability of hydrothermal time as a basis for modelling germination under field conditions. Maximum percentage germination occurred over a much narrower temperature range around the optimum temperature than previously seen for cultivated crop seed. The entire final percentage germination response to temperature in water was well described by two probit curves, and this model was extended to describe the data at all water potentials at a temperature close to the optimum. The implications of the reduction in germination at nonoptimal temperatures are discussed with respect to the interpretation of germination progress curves and conditional dormancy. After adjusting for maximum percentage germination, a hydrothermal time model was found to fit the data set well within the conditions normally encountered in horticultural seedbeds. This separation of the final percentage germination presents a flexible modelling approach that allows for the different levels of dormancy typically expressed within weed populations. By contrast with many previously reported species, S. media had a synchronous germination rate within the population at any given temperature\water potential combination. This synchronous germination of at least a proportion of the population over a wide range of temperature and water potentials might have ecological significance for the opportunistic germination behaviour of this weed species.

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“…Where a linear relationship applies, it is possible by back extrapolation to estimate the threshold or base temperature (T b ) above which development can proceed. Also, the thermal time requirement for development (S, expressed in degree days above T b ) is a constant for values of T e between T b and T o (Garcia-Huidobro et al, 1982) and is given by the reciprocal of the slope of the regression.…”

Section: mentioning

confidence: 99%

“…However, most recent research has defined the response for the whole population, either by estimating T b , S etc. for each of a set of percentiles (Garcia-Huidobro et al, 1982 ;Marshall & Squire, 1996) or representing them by a frequency distribution (Washitani & Takenaka, 1984).…”

Section: mentioning

confidence: 99%

A thermal time basis for comparing the germination requirements of some British herbaceous plants

Squire¹,

Thompson²

2000

New Phytologist

Self Cite

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The effect of temperature on germination rate was assessed for seeds of 31 wild plant species and four cultivated species growing in the UK. The temperature at which seed first germinated ranged from 2mC (Brassica rapa) to 11mC (several species). As the temperature progressively increased, the percentage of seed that germinated rapidly increased to near 100%, whereas the duration for germination progressively decreased up to the thermal optimum. Above the thermal optimum, the duration for germination initially remained constant, and then rapidly increased until the thermal maximum was exceeded when no seed germinated. To assess the effect of temperature on germination rates, the reciprocal of the duration (1\duration) for 50% germination was calculated and regressed against temperature. For most species a linear regression accounted for 90% of the variation in germination rates for temperatures up to the thermal optimum. From the regressions, the base temperatures (T b , below which no germination is expected) and the thermal constant (S, expressed in degree days) for 50% germination were calculated. The extremes were the alpine species Dryas octopetala, which had a high T b (c. 12.0mC) and low S (26 degree days), and Saxifraga tridactylites which had a low estimated T b (c. k1.8mC) and a high S (136 degree days). The estimated value of S increased with increasing percentage germination, and although S varied considerably between species with similar values of T b , a weak inverse relationship between T b and S was indicated. A thermal time approach was shown to be useful when analysing and comparing thermal requirements for germination of the seed of wild plant species. It showed, for example, that percentage germination often decreased as temperatures approached T b , and that for some seed germination ceased at temperatures well above T b .

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Time, Temperature and Germination of Pearl Millet (Pennisetum typhoidesS. & H.)

Cited by 122 publications

References 11 publications

Single-seed oxygen consumption measurements and population-based threshold models link respiration and germination rates under diverse conditions

Single-seed oxygen consumption measurements and population-based threshold models link respiration and germination rates under diverse conditions

Modelling the germination of Stellaria media using the concept of hydrothermal time

A thermal time basis for comparing the germination requirements of some British herbaceous plants

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