Population‐based threshold models describe weed germination and emergence patterns across varying temperature, moisture and oxygen conditions

Boddy, Louis G.; Bradford, Kent J.; Fischer, Albert J.

doi:10.1111/j.1365-2664.2012.02206.x

Cited by 40 publications

(64 citation statements)

References 43 publications

(90 reference statements)

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“…Bloomberg et al, 2009;Finch-Savage and Bassel, 2016). An exception to this could be where the primary interest is in the average population behaviour in an ecological context, as, for example, in modelling the seasonal timing of maximum weed emergence, where greater precision may be superfluous, or subpopulations may be multiple and undefined (Forcella et al, 2000;Grundy, 2003;Meyer and Allen, 2009;Boddy et al, 2012).…”

Section: Practical Applications Of Single-seed Respiration Measurementsmentioning

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: Practical Applications Of Single-seed Respiration Measurementsmentioning

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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“…Considering that the thermal time model accuracy in predicting emergence of a grass (Echinochloa phyllopogon) can be reduced under moderate moisture stress (Boddy et al, 2012), one cannot discard that U. brizantha seeds may have been exposed to a moderate stress caused by an excess of water evaporation from the soil due to warmer temperatures in the greenhouse. Otherwise, these data also suggest seasonality in the germination response of braquiarão seeds, which could be associated with secondary dormancy mechanisms (Bradford, 2002;Bewley et al, 2013).…”

Section: Discussionmentioning

confidence: 99%

Analysis of thermal dependence on the germination of braquiarão seeds using the thermal time model

Nakao

Cardoso

2016

Braz. J. Biol.

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This paper analyzed the thermal dependence on the germination of Urochloa brizantha (Stapf) Webster seeds under constant and fluctuating temperatures through the thermal time model. Germination tests were carried out at constant temperatures ranging from 8 °C to 41.5 °C in order to determine the model parameters: base (Tb), optimal (To) and maximum temperature (Tc) for germination; and the thermal time (θ T ) required for individual seeds to germinate. Braquiarão seeds germinate within a temperature interval from 8 °C to 41.5 °C, with an optimum range for germination estimated at 31.5 ° ≤ T ≤ 34.5 °C. Actual and expected distributions of cumulative germination percentages of U. brizantha seeds put to germinate both under controlled and uncontrolled temperature regimes were compared, and it can be seen that the model described relatively well the germination at isothermal assays; however the model failed to predict germination at a wide range of thermal fluctuations. Possible explanations for the results are discussed.Keywords: Urochloa brizantha, temperature, degrees-day. Análise da dependência térmica da germinação de braquiarão utilizando o modelo tempo térmico ResumoEste artigo analisou a dependência térmica da germinação de sementes de Urochloa brizantha em regimes de temperaturas constantes e variáveis, por intermédio do modelo do tempo térmico. Foram realizados testes de germinação em temperaturas constantes 8 °C a 41.5 °C, com o objetivo de se determinar os parâmetros do modelo: as temperaturas base (Tb), ótima (To) e máxima (Tc) de germinação, bem como a quantidade de "graus-dias" (θ G ) necessária para a germinação de sementes individuais. As sementes de braquiarão germinaram no intervalo térmico de 8 °C to 41.5 °C, sendo que a faixa ótima foi de 31.5 a 34.5 °C. As distribuições acumuladas esperadas e observadas das porcentagens de germinação de sementes de U. brizantha postas para germinar tanto em temperaturas constantes como em regime térmico não controlado foram comparadas, podendo-se observar que o modelo descreveu relativamente bem a germinação nos ensaios isotérmicos, entre o mesmo falhou em prever a germinação em situações mais amplas de variação térmica. Possíveis explicações para esses resultados são discutidas.

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“…For non-dormant E. oryzicola seed, the PBTM approach predicted with useful accuracy the germination responses of seeds to shifting temperature and water availability and their subsequent emergence from field soils [16]. However, Poaceae seeds typically possess non-deep physiological dormancy (NDPD), which indicates that seed dormancy release and increases in germination rates (speed)vary along a continuum of time and environmental conditions [17], [18].…”

Section: Introductionmentioning

confidence: 99%

“…In addition, the environmental requirements for dormancy alleviationare often population- rather than species-specific [20]–[22], thus requiring analysis at the population level. While non-dormant seeds of selected herbicide-resistant (R) and herbicide-susceptible (S) populations of E. oryzicola germinated similarly [16], information on differences in seed dormancy between R and S populations is lacking. Herbicide-resistant E. oryzicola populations trace their origin to a single introduced biotype dispersed throughout California rice fields [23] suggestingthat R populations may respond similarly to environmental variables affecting germination and dormancy.…”

Section: Introductionmentioning

confidence: 99%

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Stratification Requirements for Seed Dormancy Alleviation in a Wetland Weed

2013

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Echinochloaoryzicola(syn.E. phyllopogon) is an exotic weed of California rice paddies that has evolved resistance to multiple herbicides. Elimination of seedlingsthroughcertain weed control methods can limit the spread of this weed, but is contingent on accurate predictions of germination and emergence timing, which are influenced by seed dormancy levels.In summer annuals, dormancy can often be relieved through stratification, a period of prolonged exposure to cold and moist conditions.We used population-based threshold models to quantify the effects of stratification on seed germination of four E. Oryzicola populations at a range of water potential (Ψ) and oxygen levels. We also determined how stratification temperatures, moisture levels and durations contributed to dormancy release. Stratification released dormancy by decreasing base Ψ and hydrotimerequired for germination and by eliminating any germination sensitivity to oxygen. Stratification also increased average germination rates (GR), which were used as a proxy for relative dormancy levels. Alternating temperatures nearly doubled GR in all populations, indicating that seeds could be partially dormant despite achieving high final germination percentages. Stratification at Ψ = 0 MPa increased GR compared to stratification at lower water potentials, demonstrating that Ψ contributed to regulating dormancy release. Maximum GR occurred after 2-4 weeks of stratification at 0 MPa; GR were often more rapid for herbicide-resistant than for herbicide-susceptible seeds, implying greater dormancy in the latter. Manipulation of field conditions to promote dormancy alleviation of E. oryzicola seeds might improve the rate and uniformity of germination for seed bank depletion through seedling weed control. Our results suggest field soil saturation in winter would contribute towards E. oryzicola dormancy release and decrease the time to seedling emergence.

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Population‐based threshold models describe weed germination and emergence patterns across varying temperature, moisture and oxygen conditions

Cited by 40 publications

References 43 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

Analysis of thermal dependence on the germination of braquiarão seeds using the thermal time model

Stratification Requirements for Seed Dormancy Alleviation in a Wetland Weed

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