1. bookVolume 68 (2017): Issue 2 (June 2017)
Journal Details
License
Format
Journal
eISSN
2719-5430
First Published
30 Mar 2016
Publication timeframe
4 times per year
Languages
English
access type Open Access

Germination characteristic of Silphium perfoliatum L. seeds

Published Online: 30 Jun 2017
Volume & Issue: Volume 68 (2017) - Issue 2 (June 2017)
Page range: 73 - 79
Received: 08 Mar 2017
Accepted: 12 May 2017
Journal Details
License
Format
Journal
eISSN
2719-5430
First Published
30 Mar 2016
Publication timeframe
4 times per year
Languages
English
Summary

Silphium perfoliatum L. is a perennial and flowering crop that has been investigated in recent years for its potential as an energy plant, particularly for biogas production. A stand establishment by sowing of seeds is complicated, owing to the low germination capacity of untreated S. perfoliatum L. seeds. Consequently, germination experiments were carried out with two- to four-factor levels to determine the effect of selected factors (medium, pretreatment, light, temperature, prechilling) on dormancy and germination of S. perfoliatum L. seeds and to achieve maximum germination rate. All factors had a highly significant effect on germination. Germination experiments displayed a primary and physiological dormancy. Germination could be significantly increased by using a 0.05% GA3 solution during the imbibition phase, a light–dark cycle, alternating temperatures between 20°C and 30°C, and a wet stratification for seven days at 0°C. The experiments helped to fully exploit the germination potential and to develop a germination test method for S. perfoliatum L.

Keywords

Schlagworte

Introduction

Silphium perfoliatum L. is a perennial, tall, yellow flowering C3 plant, characterized by a wide range of valuable practical traits and has been cultivated as a medical, melliferous, fodder, ornamental, and reclamation plant (Niqueux, 1981; Neumerkel and Märtin, 1982; Troxler and Daccord, 1982; Daniel and Rompf, 1994; Kowalski and Wolski, 2005; Kowalski and Kędzia, 2007; Zhang et al., 2010). In recent years, S. perfoliatum L. has been of interest as an energy crop, especially for biogas production (Vetter et al., 2010; Bauböck et al., 2014; Mast et al., 2014; Gansberger et al., 2015). The low care requirements (after the first year) compared to annual plants, the high yield potential of the biomass, and the ecological benefits make S. perfoliatum L. a valuable renewable raw material (Gansberger et al., 2015). The labor-intensive and expensive planting of pregrown seedlings is currently the common method of stand establishment. Sowing is not feasible owing to a lack of high-quality seeds (Bauböck et al., 2014; Franzaring et al., 2015; Gansberger et al., 2015) and inappropriate seed technology. Furthermore, little is known about the germination requirements of S.perfoliatum L. (Gansberger et al., 2015). To tap the full potential of the germination capacity, the necessary environmental conditions must be identified and the dormancy, if present, must be broken. According to Sokolov and Gritsak (1972), Troxler and Daccord (1982), and Vetter et al. (2010), untreated seeds of S. perfoliatum L. show a strong dormancy, leading to an uneven and sometimes highly delayed germination. Trölenberg et al. (2012) assumed that there was no dormancy in S. perfoliatum L., but instead, quiescence. Quiescent seeds are not dormant, but are metabolically inactive because of the absence of one or more environmental factors (Bewley, 1997; Baskin and Baskin, 2004).

The aims of this work were to investigate the effect of individual factors and their levels on germination and dormancy and to determine the advisable conditions for germination, as well as to recommend a germination test method to evaluate the full germination capacity of S. perfoliatum L. seeds.

Material and methods
Seeds

Seeds of two different origins were used for the germination experiments. Lot A was harvested in September 2012 in Vienna, Austria (48°15′23″N, 16°29′5″E). Lot B was obtained from a harvest in September 2011 in Rheinstetten-Forchheim, Germany (48°58′1″N, 8°20′3″E). The viability and the theoretical germination capacity of both seed lots (rep = 4 × 50) were determined by a tetrazolium test, which also counts seeds with a physiological dormancy as viable (Baskin and Baskin, 2014). The germination potential was 97.5 ± 2.2% for lot A and 98.5 ± 0.9% for lot B, providing an excellent basis for the subsequent tests.

Model of the germination experiment

The experimental design was based on several factors and factor levels. These were chosen based on literature values for germination requirements of achenes, other members of the Asteraceae, the results of preliminary experiments, and the climate conditions of S. perfoliatum L.’s natural habitat. A full-factorial randomized design (with a total of 144 combinations) was used with two- to four-factor levels of following factors:

Medium: pleated paper (PP); top of paper (TP)

Pretreatment: water; KNO3 – 200 mg/L; GA3 (Merck KGaA) – 500 mg/L

Light (PAR between 400 and 700 nm): 24-h light; 12-h light

Temperature: 20°C; 30°C; 20/30°C

Prechilling: no prechilling; 7 days / 10°C; 7 days / 5°C; 7 days / 0°C

Each combination corresponded to a germination test method and was tested with seed lots A and B in a growth chamber (from the Kühlanlagenbau Fritz Lachmayr GesmbH, Kremsmünster, Austria). Based on sample size calculation (power 90%, α = 5%, δ = 2%), 144 analyses with eight replicates each were carried out for the two lots. Overall, 2304 observations (144 × 2 × 8) were used and each replication consisted of 50 seeds.

The evaluation was carried out after 7, 14, and 21 days. The seedlings were classified as normal seedlings, abnormal seedlings, or un-germinated seeds according to the International Rules for Seed Testing (ISTA, 2015). However, for evaluating dormancy, normal and abnormal seeds were both counted as germinated seeds.

Statistical analyses

The data set was analyzed with the statistics software SPSS V22.0. The requirements of the statistical tests were checked before and were fulfilled. Residuals were checked for normal distribution and homoscedasticity by using residual plots and statistical tests. An analysis of variance (ANOVA) was carried out with a mixed model approach to determine if the selected factors and their two-way interactions had a significant effect on germination capacity. The factors “medium, pretreatment, light, temperature and prechilling” were defined as fixed effects and the seed lot was defined as random effect. The significance level was chosen as 95%. Additionally, post-hoc analysis (Tukey-HSD) was applied for significant factors to separate the most effective factor levels.

Finally, the most promising factor levels were combined in a recommended germination test method and validated with the predicted expected values of the linear model with main effects and interactions.

Results and discussion
Germination capacity

The results of the germination capacity experiments ranged between 0 and 96% germinated seeds. With an unfavorable combination of factors, no seeds germinated, and with favorable combinations, up to 96% germinated. This effectively corresponds to the full germination potential of around 98%, which was determined in advance by a tetrazolium test. In addition, these tests showed that the embryos were fully developed and that water could enter through the seed coat to the embryo. Thus, a morphological and physical dormancy could be excluded.

Effect of selected factors and factor levels on germination

All main factors and also almost all two-way interactions had a highly significant effect on germination (Table 1). The interaction of the individual factors caused a large degree of fluctuation. The standard deviation was between 20% and 30% for all factors.

Results of the mixed model analysis (ANOVA)

Tabelle 1. Ergebnisse der gemischten Modellanalyse (ANOVA)

Fp-value
Medium14.6<0.001
Light221.3<0.001
Temperature6063.3<0.001
Pretreatment528.0<0.001
Prechilling540.7<0.001
Lot3213.7<0.001
Medium × light14.5<0.001
Light × prechilling18.0<0.001
Light × pretreatment2.70.065
Light × temperature13.9<0.001
Medium × prechilling4.30.005
Medium × pretreatment22.1<0.001
Medium × temperature75.3<0.001
Pretreatment × prechilling11.8<0.001
Temperature × prechilling39.8<0.001
Temperature × pretreatment11.5<0.001

The seeds from lot A had a germination capacity (overall factors and factor levels) of 34.0a ± 26.1%. Lot B, with 56.2b ± 27.9%, had significantly higher germination rates than lot A.

Effect of various media on germination

The mean value of germinated seeds with PP was about 1.7% higher than with TP (Table 2). Seeds in TP showed fungal infections. In contrast, the folds in the pleated paper (PP) served as a barrier, preventing fungi from growing from one seed to the next. PP seems better suited for the germination of S. perfoliatum L. seeds with their flat shape and large seed surface.

Mean value and standard deviation of germinated seeds for selected factor levels

Tabelle 2. Mittelwert und Standardabweichung gekeimter Samen für ausgewählte Faktorstufen

FactorsFactor levels
MediumPleated paper (PP)Top of paper (TP)
48.3b ± 30.7%46.6a ± 30.4%
PretreatmentWaterKNO3 (200 mg/L)GA3 (500 mg/L)
39.3a ± 29.8%47.0b ± 30.6%55.9c ± 28.9%
Light24-hours light12-hours light
44.3a ± 29.4%50.6b ± 31.4%
Temperature20°C30°C20/30°C
18.6a ± 18.7%48.5b ± 21.0%75.2c ± 20.2%
PrechillingNo prechilling7 days / 10°C7 days / 5°C7 days / 0°C
33.4a ± 26.6%48.8b ± 31.1%51.8c ± 29.9%55.7d ± 29.6%

The factor levels marked with different letters (a–d) are significantly different (α= 5%) by Tukey-HSD test. See additional data in Table 4.

Resulting germination test method for Silphium perfoliatum L. to exploit the germination potential

Tabelle 3. Resultierende Keimfähigkeitstestmethode für Silphium perfoliatum L. zur Ausschöpfung des Keimfähigkeitspotentials

SpeciesSubstrateTemperature (°C)First count (days)Final count (days)Recommendations for breaking dormancyAdditional directionsAdditional advice
S. perfoliatum L.PP20/30

Alternating temperature and light regime: first temperature 12 hours with light, second temperature 12 hours without light.

721GA3; prechill-prechill 7 days / 0°C; L/D

Alternating temperature and light regime: first temperature 12 hours with light, second temperature 12 hours without light.

Multiple Comparisons of the selected factors temperature, pretreatment and prechilling

Tabelle 4. Mehrfachvergleiche der ausgewählten Faktoren Temperatur, Vorbehandlung und Vorkühlung

95% Confidence Interval
(I) temperature(J) temperatureMean Diff. (I-J)Std. ErrorSig.Lower BoundUpper Bound
20°C30°C-29.87

The mean difference is significant at the 0.05 level.

0.514<0.001-31.08-28.67
20<=>30°C-56.560.514<0.001-57.77-55.35
30°C20°C29.870.514<0.00128.6731.08
20<=>30°C-26.690.514<0.001-27.89-25.48
20<=>30°C20°C56.560.514<0.00155.3557.77
30°C26.690.514<0.00125.4827.89
(I) pretreatment(J) pretreatment
H2OKNO3-7.760.514<0.001-8.96-6.55
GA3-16.680.514<0.001-17.89-15.48
KNO3H2O7.760.514<0.0016.558.96
GA3-8.930.514<0.001-10.13-7.72
GA3H2O16.680.514<0.00115.4817.89
KNO38.930.514<0.0017.7210.13
(I) prechilling(J) prechilling
no prechilling7d / 0°C-22.280.593<0.001-23.81-20.76
7d / 5°C-18.390.593<0.001-19.91-16.86
7d / 10°C-15.310.593<0.001-16.84-13.79
7d / 0°Cno prechilling22.280.593<0.00120.7623.81
7d / 5°C3.900.593<0.0012.375.42
7d / 10°C6.970.593<0.0015.458.50
7d / 5°Cno prechilling18.390.593<0.00116.8619.91
7d / 0°C-3.900.593<0.001-5.42-2.37
7d / 10°C3.070.593<0.0011.554.60
7d / 10°Cno prechilling15.310.593<0.00113.7916.84
7d / 0°C-6.970.593<0.001-8.50-5.45
7d / 5°C-3.070.593<0.001-4.60-1.55

Based on observed means.

The error term is Mean Square(Error) = 101.407.

Effect of various pretreatments on germination

GA3 and KNO3 solutions can affect the metabolic activity of seeds (Baskin and Baskin, 2004). Our experiments show that the treatment with GA3 and KNO3 solutions led to significantly higher germination than the untreated control with water (Table 2 and Figure 1). The greatest effect on germination capacity was achieved with GA3. GA3 has the opposite effect to abscisic acid (ABA) and the exact ratio of GA3 to ABA determines, on a plant-hormone level, whether a seed will start to germinate or remain dormant. ABA accumulates in the embryo during seed ripening and is responsible for primary dormancy (Kucera et al., 2005). In contrast, GA3 induces growth of the embryo and increases the availability of nutrients (Koornneef et al., 2002; Hilhorst, 1995). The ratio of GA3 and ABA at S. perfoliatum L. seeds has probably been shifted by adding GA3 solution and consequently the germination capacity increased. This effect suggests the presence of a physiological dormancy. The experiments of Vetter et al. (2010) and Trölenberg et al. (2012) with S. perfoliatum L. seeds using GA3 solution also showed a germination capacity close to the theoretically possible maximum.

Figure 1

Effect of various temperatures (20°C; 30°C; 20/30°C) and pretreatments (H2O; KNO3; GA3) on the germination of Silphiumperfoliatum L.

Abbildung 1. Effekt von unterschiedlichen Temperaturen (20°C; 30°C; 20/30°C) und Vorbehandlungen (H2O; KNO3; GA3) auf die Keimfähigkeit von Silphium perfoliatum L.

Effect of 12 hours and 24 hours light on germination

Light and its intensity can have a substantial effect on dormancy and germination (Oh et al., 2006). Light had a positive effect on the germination of S. perfoliatum L. during the preliminary experiments. To investigate this effect, 12- and 24-hour light variants were tested. The 12-hour light–dark cycle with a light intensity between 400 and 1200 lux resulted in significantly higher germination capacities than the 24-hour light variant (Table 2).

Effect of various temperatures on germination

Favorable environmental conditions, like specific temperature ranges, are important for germination; otherwise the seeds cannot germinate (Baskin and Baskin, 2004) or fall into secondary dormancy (Hilhorst, 1998; Finch-Savage and Leubner-Metzger, 2006). If seeds have physiological dormancy, alternating temperatures can be used to break their dormancy (Long et al., 2014).

Temperature had the greatest effect on germination capacity over all the five factors in our experiment. The differences between the temperature variants were highly significant. As Table 2 and Figure 1 show, the temperature cycles of 20/30°C every 12 hours showed distinctly more germination than constant temperatures at 20°C or 30°C. In combination with the GA3 solution, an average germination capacity of over 85% was achieved.

Trölenberg et al. (2012) extensively studied the effect of various constant and changing temperatures on the germination of S. perfoliatum L. seeds at a temperature-gradient germination table. The results showed that germination was positively influenced by higher temperatures up to 30°C and by alternating temperatures with higher amplitude.

Effect of various prechilling variants on germination

Several decades ago, Sokolov and Gritsak (1972) and Troxler and Daccord (1982) recommended sowing S. perfoliatum L. seeds in late autumn, at the latest 15–20 days before the first night frost, using freshly gathered seeds or in spring with seeds that had been stratified for 2 months. Accordingly, the factor “prechilling” was included in the model, as prechilling is particularly suitable to break the physiological dormancy (Long et al., 2014).

The results confirmed that prechilling has a positive effect on the germination capacity. The germination capacity of the variants with prechilling (7 days / 10°C; 7 days / 5°C; 7 days / 0°C) was highly significantly higher than the untreated control (no prechilling). The differences between the individual prechilling temperatures were not pronounced, but still significant. Therefore, a prechilling phase at 0°C over 7 days is advisable to achieve a high germination capacity and to break the physiological dormancy.

The results are consistent with the conclusions of Vetter et al. (2010) and Trölenberg et al. (2012). They recommend a prechilling phase at 5°C over 5 and 7 days respectively. Franzaring et al. (2014) used a four-week prechilling period in climate chambers for their growth experiments with S. perfoliatum L. The temperatures varied between 3°C and 11°C, causing stratification and breaking of the seed dormancy.

Germination characteristic and germination test method of S. perfoliatum L

The most promising factor levels were combined in a germination test method, which allows the assessment of the germination capacity of S. perfoliatum L. seeds (Table 3). These results were confirmed by using the predicted outcome of the linear model with main effects and interactions. The only deviation between the results of the ANOVA and post-hoc tests and the linear model could be found for the factor “type of paper.” However, the difference between the mean values of the factor medium was minor (Table 2). Consequently, the choice between the paper substrates seems to be of less importance. The use of PP is recommended, due to the reduced fungal growth and the smaller number of abnormal seedlings in comparison to TP.

Conclusion

The results of the germination characteristic of S. perfoliatum L. indicate that a targeted and optimized pretreatment is required for a fast and complete germination. The germination test method (Table 3) includes various treatments for breaking the physiological dormancy. The germination capacity was increased considerably with the use of GA3 solutions, light, alternating temperatures and prechilling, and their modes of action suggest a pronounced physiological dormancy in fresh S. perfoliatum L. seeds.

In future experiments, for example, the influence of seed moisture content, harvest date and seed age on dormancy and different seed preparation should be tested and the laboratory-scale results need to be confirmed at field scale. Therefore applying additional pretreatments, like other biologically active compounds, priming and pelleting, are of great interest. For this, the results of this work can be incorporated.

Figure 1

Effect of various temperatures (20°C; 30°C; 20/30°C) and pretreatments (H2O; KNO3; GA3) on the germination of Silphiumperfoliatum L.Abbildung 1. Effekt von unterschiedlichen Temperaturen (20°C; 30°C; 20/30°C) und Vorbehandlungen (H2O; KNO3; GA3) auf die Keimfähigkeit von Silphium perfoliatum L.
Effect of various temperatures (20°C; 30°C; 20/30°C) and pretreatments (H2O; KNO3; GA3) on the germination of Silphiumperfoliatum L.Abbildung 1. Effekt von unterschiedlichen Temperaturen (20°C; 30°C; 20/30°C) und Vorbehandlungen (H2O; KNO3; GA3) auf die Keimfähigkeit von Silphium perfoliatum L.

Mean value and standard deviation of germinated seeds for selected factor levelsTabelle 2. Mittelwert und Standardabweichung gekeimter Samen für ausgewählte Faktorstufen

FactorsFactor levels
MediumPleated paper (PP)Top of paper (TP)
48.3b ± 30.7%46.6a ± 30.4%
PretreatmentWaterKNO3 (200 mg/L)GA3 (500 mg/L)
39.3a ± 29.8%47.0b ± 30.6%55.9c ± 28.9%
Light24-hours light12-hours light
44.3a ± 29.4%50.6b ± 31.4%
Temperature20°C30°C20/30°C
18.6a ± 18.7%48.5b ± 21.0%75.2c ± 20.2%
PrechillingNo prechilling7 days / 10°C7 days / 5°C7 days / 0°C
33.4a ± 26.6%48.8b ± 31.1%51.8c ± 29.9%55.7d ± 29.6%

Multiple Comparisons of the selected factors temperature, pretreatment and prechillingTabelle 4. Mehrfachvergleiche der ausgewählten Faktoren Temperatur, Vorbehandlung und Vorkühlung

95% Confidence Interval
(I) temperature(J) temperatureMean Diff. (I-J)Std. ErrorSig.Lower BoundUpper Bound
20°C30°C-29.87

The mean difference is significant at the 0.05 level.

0.514<0.001-31.08-28.67
20<=>30°C-56.560.514<0.001-57.77-55.35
30°C20°C29.870.514<0.00128.6731.08
20<=>30°C-26.690.514<0.001-27.89-25.48
20<=>30°C20°C56.560.514<0.00155.3557.77
30°C26.690.514<0.00125.4827.89
(I) pretreatment(J) pretreatment
H2OKNO3-7.760.514<0.001-8.96-6.55
GA3-16.680.514<0.001-17.89-15.48
KNO3H2O7.760.514<0.0016.558.96
GA3-8.930.514<0.001-10.13-7.72
GA3H2O16.680.514<0.00115.4817.89
KNO38.930.514<0.0017.7210.13
(I) prechilling(J) prechilling
no prechilling7d / 0°C-22.280.593<0.001-23.81-20.76
7d / 5°C-18.390.593<0.001-19.91-16.86
7d / 10°C-15.310.593<0.001-16.84-13.79
7d / 0°Cno prechilling22.280.593<0.00120.7623.81
7d / 5°C3.900.593<0.0012.375.42
7d / 10°C6.970.593<0.0015.458.50
7d / 5°Cno prechilling18.390.593<0.00116.8619.91
7d / 0°C-3.900.593<0.001-5.42-2.37
7d / 10°C3.070.593<0.0011.554.60
7d / 10°Cno prechilling15.310.593<0.00113.7916.84
7d / 0°C-6.970.593<0.001-8.50-5.45
7d / 5°C-3.070.593<0.001-4.60-1.55

Resulting germination test method for Silphium perfoliatum L. to exploit the germination potentialTabelle 3. Resultierende Keimfähigkeitstestmethode für Silphium perfoliatum L. zur Ausschöpfung des Keimfähigkeitspotentials

SpeciesSubstrateTemperature (°C)First count (days)Final count (days)Recommendations for breaking dormancyAdditional directionsAdditional advice
S. perfoliatum L.PP20/30

Alternating temperature and light regime: first temperature 12 hours with light, second temperature 12 hours without light.

721GA3; prechill-prechill 7 days / 0°C; L/D

Alternating temperature and light regime: first temperature 12 hours with light, second temperature 12 hours without light.

Results of the mixed model analysis (ANOVA)Tabelle 1. Ergebnisse der gemischten Modellanalyse (ANOVA)

Fp-value
Medium14.6<0.001
Light221.3<0.001
Temperature6063.3<0.001
Pretreatment528.0<0.001
Prechilling540.7<0.001
Lot3213.7<0.001
Medium × light14.5<0.001
Light × prechilling18.0<0.001
Light × pretreatment2.70.065
Light × temperature13.9<0.001
Medium × prechilling4.30.005
Medium × pretreatment22.1<0.001
Medium × temperature75.3<0.001
Pretreatment × prechilling11.8<0.001
Temperature × prechilling39.8<0.001
Temperature × pretreatment11.5<0.001

Baskin, C.C. and J.M. Baskin (2014): Seeds: Ecology, Biogeography, and Evolution of Dormancy and Germination. 2nd ed., Academic Press, San Diego, USA.BaskinC.C.BaskinJ.M.2014Seeds: Ecology, Biogeographyand Evolution of Dormancy and Germination2ndAcademic PressSan Diego, USASearch in Google Scholar

Baskin, J.M. and C.C. Baskin (2004): A classification system for seed dormancy. Seed Science Research 14, 1–16.BaskinJ.M.BaskinC.C.2004A classification system for seed dormancySeed Science Research1411610.1079/SSR2003150Search in Google Scholar

Bauböck, R., Karpenstein-Machan, M. and M. Kappas (2014): Computing the biomass potentials for maize and two alternative energy crops, triticale and cup plant (Silphium perfoliatum L.), with the crop model Bio-STAR in the region of Hannover (Germany). Environmental Sciences Europe 26, 1–12.BauböckR.Karpenstein-MachanM.KappasM.2014Computing the biomass potentials for maize and two alternative energy crops, triticale and cup plant (Silphium perfoliatum L.), with the crop model Bio-STAR in the region of Hannover (Germany)Environmental Sciences Europe2611210.1186/s12302-014-0019-0Search in Google Scholar

Bewley, J.D. (1997): Seed Germination and Dormancy. The Plant Cell 9, 1055–1066.BewleyJ.D.1997Seed Germination and DormancyThe Plant Cell91055106610.1105/tpc.9.7.1055Search in Google Scholar

Daniel, P. and R. Rompf (1994): Possibilities and limits in the utilization of Silphium perfoliatum as a fodder plant, renewable raw material and a landscape conservation plant. Agribiological research 47, 345–353.DanielP.RompfR.1994Possibilities and limits in the utilization of Silphium perfoliatum as a fodder plant, renewable raw material and a landscape conservation plantAgribiological research47345353Search in Google Scholar

Finch-Savage, W.E. and G. Leubner-Metzger (2006): Seed dormancy and the control of germination. New Phytologist 171, 501–523.Finch-SavageW.E.Leubner-MetzgerG.2006Seed dormancy and the control of germinationNew Phytologist17150152310.1111/j.1469-8137.2006.01787.xSearch in Google Scholar

Franzaring, J., Holz, I., Kauf, Z. and A. Fangmeier (2015): Responses of the novel bioenergy plant species Sida hermaphrodita (L.) Rusby and Silphium perfoliatum L. to CO2 fertilization at different temperatures and water supply. Biomass and Bioenergy 81, 574–583.FranzaringJ.HolzI.KaufZ.FangmeierA.2015Responses of the novel bioenergy plant species Sida hermaphrodita (L.) Rusby and Silphium perfoliatum L. to CO2 fertilization at different temperatures and water supplyBiomass and Bioenergy8157458310.1016/j.biombioe.2015.07.031Search in Google Scholar

Franzaring, J., Schmid, I., Bäuerle, L., Gensheimer, G. and A. Fangmeier (2014): Investigations on plant functional traits, epidermal structures and the ecophysiology of the novel bioenergy species Sida hermaphrodita Rusby and Silphium perfoliatum L. Journal of Applied Botany and Food Quality 87, 36–45.FranzaringJ.SchmidI.BäuerleL.GensheimerG.FangmeierA.2014Investigations on plant functional traits, epidermal structures and the ecophysiology of the novel bioenergy species Sida hermaphrodita Rusby and Silphium perfoliatum LJournal of Applied Botany and Food Quality873645Search in Google Scholar

Gansberger, M., Montgomery, L.F.R. and P. Liebhard (2015): Botanical characteristics, crop management and potential of Silphium perfoliatum L. as a renewable resource for biogas production: a review. Industrial Crops and Products 63, 362–372.GansbergerM.MontgomeryL.F.R.LiebhardP.2015Botanical characteristics, crop management and potential of Silphium perfoliatum L. as a renewable resource for biogas production: a reviewIndustrial Crops and Products6336237210.1016/j.indcrop.2014.09.047Search in Google Scholar

ISTA (2015): International Rules for Seed Testing 2015. Chapter 5: The germination test. i–5-56.ISTA2015International Rules for Seed Testing 20155The germination testi556Search in Google Scholar

Hilhorst, H.W.M. (1995): A critical update on seed dormancy. I. Primary dormancy. Seed Science Research 5, 61–73.HilhorstH.W.M.1995A critical update on seed dormancy. I. Primary dormancySeed Science Research5617310.1017/S0960258500002634Search in Google Scholar

Hilhorst, H.W.M. (1998): The regulation of secondary dormancy. The membrane hypothesis revisited. Seed Science Research 8, 77–90.HilhorstH.W.M.1998The regulation of secondary dormancy. The membrane hypothesis revisitedSeed Science Research8779010.1017/S0960258500003974Search in Google Scholar

Koornneef, M., Bentsink, L. and H. Hilhorst (2002): Seed dormancy and germination. Current Opinion in Plant Biology 5, 33–36.KoornneefM.BentsinkL.HilhorstH.2002Seed dormancy and germinationCurrent Opinion in Plant Biology5333610.1016/S1369-5266(01)00219-9Search in Google Scholar

Kowalski, R. and B. Kędzia (2007): Antibacterial activity of Silphium perfoliatum extracts. Pharmaceutical Biology 45, 494–500.KowalskiR.KędziaB.2007Antibacterial activity of Silphium perfoliatum extractsPharmaceutical Biology4549450010.1080/13880200701389409Search in Google Scholar

Kowalski, R. and T. Wolski (2005): The chemical composition of essential oils of Silphium perfoliatum L. Flavour and Fragrance Journal 20, 306–310.KowalskiR.WolskiT.2005The chemical composition of essential oils of Silphium perfoliatum LFlavour and Fragrance Journal2030631010.1002/ffj.1418Search in Google Scholar

Kucera, B., Cohn, M.A. and G. Leubner-Metzger (2005): Plant hormone interactions during seed dormancy release and germination. Seed Science Research 15, 281–307.KuceraB.CohnM.A.Leubner-MetzgerG.2005Plant hormone interactions during seed dormancy release and germinationSeed Science Research1528130710.1079/SSR2005218Search in Google Scholar

Long, R.L., Gorecki, M.J., Renton, M., Scott, J.K., Colville, L., Goggin, D.E., Commander, L.E., Westcott, D.A., Cherry, H. and W.E. Finch-Savage (2014): The ecophysiology of seed persistence: a mechanistic view of the journey to germination or demise. Biological Reviews of the Cambridge Philosophical Society 90, 31–59.LongR.L.GoreckiM.J.RentonM.ScottJ.K.ColvilleL.GogginD.E.CommanderL.E.WestcottD.A.CherryH.Finch-SavageW.E.2014The ecophysiology of seed persistence: a mechanistic view of the journey to germination or demiseBiological Reviews of the Cambridge Philosophical Society90315910.1111/brv.1209524618017Search in Google Scholar

Mast, B., Lemmer, A., Oechsner, H., Reinhardt-Hanisch, A., Claupein, W. and S. Graeff-Hönninger (2014): Methane yield potential of novel perennial biogas crops influenced by harvest date. Industrial Crops and Products 58, 194–203.MastB.LemmerA.OechsnerH.Reinhardt-HanischA.ClaupeinW.Graeff-HönningerS.2014Methane yield potential of novel perennial biogas crops influenced by harvest dateIndustrial Crops and Products5819420310.1016/j.indcrop.2014.04.017Search in Google Scholar

Neumerkel, W. and B. Märtin (1982): Silphium (Silphium perfoliatum L.) - a new feed plant. Archives of Agronomy and Soil Science 26, 261–271.NeumerkelW.MärtinB.1982Silphium (Silphium perfoliatum L.) - a new feed plantArchives of Agronomy and Soil Science26261271Search in Google Scholar

Niqueux, M. (1981): A new forage plant: Silphium perfoliatum L. Fourrages 87, 119–136.NiqueuxM.1981A new forage plantSilphium perfoliatum L. Fourrages87119136Search in Google Scholar

Oh, E., Yamaguchi, S., Kamiya, Y., Bae, G., Chung, W.I. and G. Choi (2006): Light activates the degradation of PIL5 protein to promote seed germination through gibberellin in Arabidopsis. The Plant Journal 47, 124–139.OhE.YamaguchiS.KamiyaY.BaeG.ChungW.I.ChoiG.2006Light activates the degradation of PIL5 protein to promote seed germination through gibberellin in ArabidopsisThe Plant Journal4712413910.1111/j.1365-313X.2006.02773.x16740147Search in Google Scholar

Sokolov, V.S. and Z.I. Gritsak (1972): Silphium – a valuable fodder and nectariferous crop. World Crops 24, 299–301.SokolovV.S.GritsakZ.I.1972Silphium – a valuable fodder and nectariferous cropWorld Crops24299301Search in Google Scholar

Trölenberg, S.D., Kruse, M. and A. Jonitz (2012): Verbesserung der Saatgutqualitätbei der Durchwachsenen Silphie (Silphium perfoliatum L.). VDLUFA-Verlag, Darmstadt, Germany.TrölenbergS.D.KruseM.JonitzA.2012Verbesserung der Saatgutqualitätbei der Durchwachsenen Silphie (Silphium perfoliatum L.)VDLUFA-VerlagDarmstadt, GermanySearch in Google Scholar

Troxler, J. and R. Daccord (1982): Silphium perfoliatum L.: An interesting fodder? Revue Suisse d’Agriculture 14, 279–281.TroxlerJ.RDaccord.1982Silphium perfoliatum L.: An interesting fodder?Revue Suisse d’Agriculture14279281Search in Google Scholar

Vetter, A., Conrad, M. and A. Biertümpfel (2010): Optimierung des Anbauverfahrens für Durchwachsene Silphie (Silphium perfoliatum L.) als Kofermentpflanze in Biogasanlagen sowie Überführung in die landwirtschaftliche Praxis. Thüringer Landesanstalt für Landwirtschaft, Jena, Germany.VetterA.ConradM.BiertümpfelA.2010Optimierung des Anbauverfahrens für Durchwachsene Silphie (Silphium perfoliatum L.) als Kofermentpflanze in Biogasanlagen sowie Überführung in die landwirtschaftliche PraxisThüringer Landesanstalt für LandwirtschaftJenaGermanySearch in Google Scholar

Zhang, X., Xia, H., Li, Z., Zhuang, P. and B. Gao (2010): Potential of four forage grasses in remediation of Cd and Zn contaminated soils. Bioresource Technology 101, 2063–2066.ZhangX.XiaH.LiZ.ZhuangP.GaoB.2010Potential of four forage grasses in remediation of Cd and Zn contaminated soilsBioresource Technology1012063206610.1016/j.biortech.2009.11.06520005700Search in Google Scholar

Recommended articles from Trend MD

Plan your remote conference with Sciendo