Germination response of black nightshade (Solanum nigrum) to temperature and the establishment of a thermal time model

Black nightshade (Solanum nigrum L.) is one of the worst weeds in crop fields, and it spreads mainly by the dispersal of seeds. Temperature is one of the key environmental factors affecting seed germination. We investigated the seed germination response to temperature in six populations of S. nigrum from mid to northern China and derived mathematical models from germination data. The results showed that S. nigrum seeds exhibit distinct germination responses to temperature within the range of 15 to 35 °C. The optimum temperatures for the populations XJ1600, JL1697 and HLJ2134 were 30 °C, and those for the populations NMG1704, HN2160 and LN2209 were 25 °C, 20 °C and 15 °C, respectively. Based on the nonlinear fitting and thermal time models, the predicted base temperatures of the six populations ranged from 2.3 to 6.4 °C, and the required accumulated growing degree days (GDD) ranged from 50.3 to 106.0 °C·d. The base temperatures and the accumulated GDD for germination differed among populations, and there was a significant negative correlation. HLJ2134 population required a high base temperature and accumulated GDD for germination, indicating that it might highly adapted to a warmer and moister environment. Based on the different germination responses of S. nigrum populations to temperature, the thermal time model reflects an innate relationship between base temperature and accumulated GDD required for initiation of seed germination, which provides a better basis for predicting seedling emergence and the timing for optimal control of S. nigrum under field conditions.

Does seed heteromorphism affect the critical temperature thresholds for wild mustard (Sinapis arvensis L.) germination? A modeling approach

Wild mustard (Sinapis arvensis L.) is well-known as a serious weed of cultivated land, particularly in cereal crops. It produces large amounts of heteromorphic (black and brown) seeds. This study aimed to estimate the critical temperature thresholds of wild mustard heteromorphic seeds. For this purpose, a novel Weibull-based thermal time model was developed, which was applied to compare the germination characteristics of the heteromorphic seeds of wild mustard. Germination was investigated by exposing the seeds to eight constant temperatures of 7.5, 10, 15, 20, 25, 30, 35, and 37.5 °C. Over both the sub- and supra-optimal ranges, the proposed model reasonably explained the germination patterns of both seed types in response to temperature. Heteromorphic seeds of wild mustard exhibited different germination behaviors in response to temperature. Brown seeds were more cold-tolerant and could germinate rapidly to a high percentage (68%) in a wider range of temperature environments (2.78-38.05 °C); black seeds germinated at a narrower temperature range (4.99-37.97 °C), and a large proportion of seeds remained dormant (77%). These differences can lead to the temporal distribution of seed germination throughout the growing season.

Application of the thermal time model for different Typha domingensis populations

Background: Cattail (Typha domingensis Pers.) is a perennial emergent plant which is used in Green Floating Filters (GFFs), one of the most innovative systems of wastewater treatment to bioremediate eutrophic waters and produce biomass as biofuel feedstocks. The establishment of cattails in GFFs depends on the seed germination and plant responses under conditions of a new habitat. This study analysed the germination responses of four different populations of cattails through a thermal time model to know their basic parameters of germination and which population would be more adapted to the conditions tested.Results: Seeds from the Badajoz (Ba), Cuenca (Cu), Madrid (Ma), Seville (Se) and Toledo (To) populations were exposed to different thermal regimes (constant, and alternating temperatures between 15 and 30°C) and different darkness treatments (between 0 and 20 days with 24h dark photoperiod, then exposed to light with 12h light/dark photoperiod) to determine the parameters of the thermal model from germination levels in each treatment. To population was used to validate the thermal time parameters of other populations. Regardless of the other parameters, no germination occurred in total darkness. The mean value of base temperature (Tb) was 16.4±0.2°C in all treatments. Optimum temperature (To) values in Ma and Ba were 25°C, and those in Cu and Se were 22.5°C. The germination response decreased when the temperature approached Tb and increased when it was close to To. In comparison to alternating temperatures, constant temperatures had the highest germination response and lowest thermal time (θT(50)). Darkness treatments had a direct relationship with θT(50). The population origin also affected seed germination; Cu had the highest values of To and germination response but had a lower θT(50), which coincides with the lowest mean ambient temperatures. Conclusion : According to these results, the germination response of cattails was high in all populations under optimal conditions but was affected to a greater or lesser extent depending on thermal regimes, darkness treatments, and populations. The thermal time model allowed us to determine that To was between 22.5-25ºC and that Cu is the best population regarding the germination response under the conditions tested.

Application of the thermal time model for different Typha domingensis populations

BackgroundCattail (Typha domingensis Pers.) is a perennial emergent plant which is used in Green Floating Filters (GFFs), one of the most innovative systems of wastewater treatment to bioremediate eutrophic waters and produce biomass as biofuel feedstocks. The establishment of cattails in GFFs depends on the seed germination and plant responses under conditions of a new habitat. This study analysed the germination response of four different populations of cattails through a thermal time model to determine which population would have the fastest germination for establishment in GFFs.ResultsSeeds from the Badajoz (Ba), Cuenca (Cu), Madrid (Ma), Seville (Se) and Toledo (To) populations were exposed to different thermal regimes (constant, and alternating temperatures between 15 and 30°C) and differents darkness treatments (between 0 and 20 days with 24h dark photoperiod, then exposed to light with 12h light/dark photoperiod) to determine the parameters of the thermal model from germination levels in each treatment. To population was used to validate the thermal time parameters of other populations. Regardless of the other parameters, no germination occurred in total darkness. The mean value of base temperature (Tb) was 16.4±0.2°C in all treatments. Optimum temperature (To) values in Ma and Ba were 25°C, and those in Cu and Se were 22.5°C. The germination response decreased when the temperature approached Tb and increased when it was close to To. In comparison to alternating temperatures, constant temperatures had the highest germination response and lowest thermal time (θT(50)). Darkness treatments had a direct relationship with θT(50). The population origin also affected seed germination; Cu had the highest values of To and germination response but had a lower θT(50), which coincides with the lowest mean ambient temperatures.Conclusion According to these results, the germination response of cattails was high in all populations under optimal conditions but was affected to a greater or lesser extent depending on thermal regimes, darkness treatments, and populations. The thermal time model allowed us to determine that To was between 22.5-25ºC. In comparison to other populations, Cu is the best population for establishment in GFFs due to its high germination response under the conditions tested.

Application of the thermal time model for different Typha domingensis populations

BackgroundTypha domingensis Pers. is a perennial emergent plant that in comparison to other Typha species, produces more biomass. This species is used in Green Floating Filters (GFFs), one of the most innovative systems of wastewater treatment to bioremediate eutrophic waters and produce biomass as biofuel feedstocks. The establishment of a GFF depends on the seed germination and plant responses under conditions of a new habitat. This study analysed the germination response of four different populations of T. domingensis through a thermal time model to determine which population would have the fastest germination for establishment in a GFF.ResultsSeeds from the Badajoz (Ba), Cuenca (Cu), Madrid (Ma) and Seville (Se) populations were exposed to different thermal regimes (constant and alternating temperatures between 15 and 30°C) and photoperiods (0, 3, 5, 7,10 and 20 days in darkness) to determine the parameters of the thermal model. Regardless of other parameters, no germination occurred in total darkness (20 days). The mean value of the base temperature (Tb) was 16.4±0.2°C in all treatments. The optimum temperature (To) values in Ma and Ba were 25°C, and those in Cu and Se were 22.5°C. The germination response decreased when the temperature approached Tb and increased when it was close to To. In comparison to temperatures with a ΔT= 5°C or 10°C, those with a ΔT= 15°C or ΔT= 0°C had the highest germination response and lowest thermal time (θT(50)). The photoperiod had a relationship with θT(50), but it was not proportional. The populations also affected germination; Cu had the highest values of To and germination response but had a lower θT(50). which coincides with the lowest mean ambient temperatures.Conclusion According to these results, the germination response of T. domingensis under optimal conditions was high in all populations but was affected to a greater or lesser extent depending on thermal regimes, photoperiods, and population. The thermal time model allowed us to determine that in comparison to other populations, Cu is the best population for establishment in a GFF due to its high germination response under the conditions tested.

Utilizing a Thermal Time Model to Estimate Safe Times to Transplant Tilia Trees

City trees planted in parks and along streets are typically grown to large size in nurseries before being transplanted to their final growing sites. According to tendering rules within the European Union (EU), any business may compete for public contracts in any EU country, and this applies to purchases of valuable lots of nursery trees. There is however a risk of poor transplanting success if the trees are imported from very distant locations with a different pace of spring development. The aim of this study was to implement a Thermal Time model to predict the spring development of Tilia trees to find out in which geographical area the spring development is sufficiently similar to conditions in southern Finland, so that the success of transplantation of the trees is not unduly risked. We used phenological observations collected at the International Phenological Gardens (IPGs) over the whole of Europe, together with ERA-Interim weather data to estimate the model parameters, and then used the same date to predict the onset of leaf unfolding ofTilia during the years 1980 to 2015. Producing maps of phenological development of Tilia, we concluded that there are no large risks of frost damage if tree import area is limited to northern parts of Baltics or to the west coast of Scandinavia.