The role of temperature in the seed germination of two species of the Solanum nigrum complex

Summary The seed dormancy cycle in Solanum nigrum and Solanum physalifolium was studied in relation to seasonal temperature. Seed lots of both species were buried in pots outdoors in a randomised complete block design with four replicates from November 2004 to November 2006. At regular intervals, samples of the seeds were randomly exhumed and tested for germination in incubators at three temperatures and light/darkness regimes. For both species, low winter temperature weakened dormancy and high temperature strengthened it. Dormancy induction mainly occurred from August to October in both species after experiencing warm temperatures. An exception from the general pattern of seed dormancy was however observed; seed germination percentages were temporarily reduced in early spring, followed by a peak in germination, before the main period of strong dormancy in S. nigrum. The same phenomenon was observed in S. physalifolium during June in the first year. This short‐lived dormancy induction might explain the late emergence of the species. Seed dormancy enables the species to maximise its chance of survival by regulating germination timing to favourable conditions. Therefore, information on the dormancy cycle can be used to predict seedling emergence and optimise weed control operations.

Section: Discussionsupporting

confidence: 92%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Seasonal changes in seed dormancy of Solanum nigrum and Solanum physalifolium

Taab

Andersson

2009

“…, 2000), 11.7°C for E. crus‐galli (Martinkova et al. , 2006), 10.0°C for S. nigrum (Del Monte & Tarquis, 1997), 6.7°C for S. oleraceus (Steinmaus et al. , 2000), 12.0°C for S. halepense (Holt & Orcutt, 1996), and 9.5°C for X. strumarium (Alm et al.…”

Section: Methodsmentioning

confidence: 99%

Predicting weed emergence in maize crops under two contrasting climatic conditions

Dorado

Sousa²,

Calha³

et al. 2009

Summary Predictive empirical models of the timing of emergence were developed for ten major weed species in maize crops. Monitoring of seedling emergence was performed over two years in two maize fields located in Central Spain and Tagus Valley in Portugal. Thermal time was used as the independent variable for predicting cumulative emergence. Different non‐linear growth curves were fitted to the data sets of cumulative percent emergence for the different species, sites and years using genetic algorithms. Based on their emergence patterns, weed species were arranged into three groups. Species with early‐season emergence (Abutilon theophrasti, Xanthium strumarium, Datura stramonium, Datura ferox, Sorghum halepense, Digitaria sanguinalis and Echinochloa crus‐galli) reached 70% emergence with less than 700 growing day degrees (GDD). Species with whole‐season emergence (Cyperus rotundus and Solanum nigrum) started early their emergence processes but the emergence continued throughout the maize life‐cycle; they required up to 1300 GDD to reach 70% emergence. The only species with late‐season emergence was Sonchus oleraceus; it required more than 1300 GDD to reach 70% emergence. The results obtained in our experiments have shown a good synchrony between the predictions obtained in different years in the same site. However, no single model was able to predict the timing of emergence in two sites with different environmental conditions, challenging the hypothesis that a single general model, based on temperature only, can be used to predict weed emergence in different geographical locations.

“…(1984) reported germination of S. nigrum at constant temperatures from 20 to 35°C in light. Del Monte and Tarquis (1997) showed that populations of S. nigrum and S. physalifolium germinate at constant temperatures with higher rates in the first species.…”

Section: Introductionmentioning

confidence: 99%

Seed dormancy dynamics and germination characteristics of Solanum nigrum

Taab

Andersson

2009

Four experiments were conducted to study seed dormancy and germination requirements in Solanum nigrum. In Expt 1, seeds were stratified at different constant and stepwise rising temperatures and their germinability was tested at three germination regimes at weekly intervals. In Expts 2-4, seeds dry stored at 4°C and stratified at 5 and 15°C were tested at constant temperatures, as well as fluctuating temperatures with constant and increasing amplitudes. Results suggest that the rate of dormancy release increased with increasing temperatures ranging from 4.5 to 18.6°C. However, prolonged stratification at higher temperatures caused subsequent induction of dormancy. When tested at constant temperatures, stratified seeds germinated between 18 and 34°C, with the optimum between 26 and 30°C, while dry-stored seeds showed no germination. Fluctuating temperatures, with amplitudes ranging from 5 to 15°C, promoted germination of seeds from all treatments. The dormancy dynamics and germination characteristics of the species will have implications for its survival and establishment. This information can be used to predict time of emergence and, thus, improve control of the species in weed management systems.