In: D. Marčić, M. Glavendekić, P. Nicot (Eds.) Proceedings of the 7th Congress on Plant Protection. Plant Protection Society of Serbia, IOBC-EPRS, IOBC-WPRS, Belgrade, 2015, pp. 311 - 315
THE INFLUENCE OF TEMPERATURE ON GERMINATION OF ragweed (Ambrosia artemisiifolia L.), wild oat (Avena fatua L.), common cocklebur (Xanthium strumarium L.) AND weedy sunflower (Helianthus annuus L.)
Markola Saulić, Darko Stojićević, Dragana Božić and Sava Vrbničanin* University of Belgrade, Faculty of Agriculture, Belgrade – Zemun, Serbia *[email protected]
ABSTRACT
In the laboratory conditions, the effect of temperature on germination of four invasive species in the territory of the Republic of Serbia is observed: wild oat (Avena fatua L.), ragweed (Ambrosia artemisiifolia L.), common cocklebur (Xanthium strumarium L.) and weedy sunflower (Helianthus annuus L.). Seeds were germinated seven days in the dark and at various temperatures from 10-35°C. Based on the established percentage of germination rate and germination, it was concluded that temperatures had different effects on seed germination. Key words: temperature, seed germination
Introduction contained in burs. Lower seed isn’t dormant, while the top seed is dormant and it doesn’t germinate for months Seed germination depends on the environmental to a year after maturity (Barton, 1962). It was late spring conditions and the characteristics of the seeds, as well species whose seeds germinate and sprout at the optimum as their interactions. Awareness of the germination of average daily temperature 14-16°C (Vrbničanin and certain plant species is very useful for understanding the Šinžar, 2003). Growing weedy sunflower (Helianthus potential and invasiveness of those weeds. Each plant annuus L.) is also late spring species and it can be in species for germination requires specific environmental the soil for many years to maintain germination (Vischi conditions, including soil moisture, temperature, oxygen et al. 2006). Ragweed (Ambrosia artemisiifolia L.) availability, presence/absence of light, microbial activity belongs to the spring species and seeds germinate at and nitrate content in soil (Baskin and Baskin, 1990). temperatures ranging from 6 to 32°C, and the optimum Some authors believed that temperature is a major factor is achieved at 20-22°C (Vrbničanin and Šinžar, 2003), for the germination process (Forcella, 1998). while illumination increases germination (Ristić et Wild oat (Avena fatua L.) is a species of early spring al., 2008). It was confirmed that ragweed seeds can that germinate and sprout at a minimum temperature of germinate in conditions that are unfavorable for some 1-2ºC (with optimum temperature for germination 16- other species, such as soil salinity (DiTommaso, 2004). 20ºC) (Vrbničanin and Šinžar, 2003). For this species Seeds of ragweed cannot germinate immediately after very strong dormancy is typical and it was used as a model the decline of the mother plant, due to very strong plant for reseracing dormancy (Foley, 1992). Common primary dormancy (Baskin and Baskin, 1980). cocklebur (Xanthium strumarium L.) is one of the most Germination occurs after stratification during winter. common, competing weeds found in crops across Serbia The seeds that did not germinate in the spring, enter (Vrbničanin et al., 2009). Common cocklebur seed is the secondary dormancy and cannot germinate until
311 they live again a phase of stratifaction next winter Results (Milanova and Nakova, 2002). It has been shown that in laboratory conditions seed germination was After seven days of seeds imbibition in the dark higher due to stratification at -8°C compared to +4 °C at different temperature regimes, generally the best (Konstatinović et al., 2013). germination had seed of wild oat. Even 90% of the seeds Despite numerous studies, the germination of weed of this species germinated, while maximum germination seeds, as well as the influence of various biotic and abiotic of ragweed seeds was actually only 30%. The seeds of factors on the complexity of the process of germination, common cocklebur germinated with 43.33% and 40% there is a need for such research. The aim of this study of sunflower (Table 1). was to evaluate the germination of four weed species (wild Seeds of wild oat has the best germination at a oat, ragweed, weedy sunflower and common cocklebur). temperature of 10°C (90%) and the lowest at 35°C Knowing the optimum temperature range in which a (6.87%). Weedy sunflower seeds and common cocklebur specific weed species germinates could shed light on the have mutually similar results, ie. it turns out that the biology of such a species and can be useful in predicting optimum temperature for germination of both types significant flushes of emergence, leading to more pro- active and practicable control measures. was 25°C. At this temperature, weedy sunflower showed 40% germination and common cocklebur of 43.33%. However temperature of 10°C is not at all conducive Material and Methods to germination of common cocklebur because no seeds germinated. To weedy sunflower the temperature of For the purposes of this research, seeds of wild oat, 30°C was at least corresponded, only 5% of the seeds has ragweed, common cocklebur and weedy sunflower were germinated. The highest percentage of seed germination collected from different localities in Serbia. Namely, seeds of ragweed was recorded at a temperature of 25°C of wild oat collected at the locality Radmilovac, seeds of (30%), while at a temperature of 10°C not a single seed ragweed at the village Čestereg, and seeds of common germinated cocklebur and weedy sunflower at the locality Surčin. Analysis (t-test) data on % of germination of wild The plants were removed at the stage of physical maturity oats and ragweed at different temperatures showed of seeds. From collecting separated seeds to starting statistically significant differences (P<0.01) in the experiment, they are stored at room temperature germination between different temperatures in most (20-25°C) about six months. In 9 cm diametar Petri cases, while the weedy sunflower had no statistically dishes with filter paper 5 burn of common cocklebur significant difference between the following treatments: and 20 weedy sunflower seeds, wild oat and ragweed 10 and 15°C; 10 and 20°C; 15 and 20°C; 15 and were placed, and then it was added 5 ml of distilled 25°C; 20 and 25 and 30°C and 35°C. Differences in water. The germination was studied in an aincubator germination between the temperatures of common (Vinder CE and Memmert) in the dark at the following cocklebur in most cases were not statistically significant temperatures: 10, 15, 20, 25, 30, 35°C (P>0.05) (Table 2). Germination was monitored every day during seven Based on the daily readings of examined germination of days. Each treatment consisted of 2 sets of 8 replications weed species germination rates were calculated to indicate for all species. the dynamics of seed germination. The germination rate The data were analyzed and calculated the percentage of wild oat seed was highest at 25°C (7.90 seeds/day) and of seed germination and the germination rate by the the lowest at a temperature of 30°C (0.79 seeds/day). At following formula: a temperature of 10°C at common cocklebur seed, was noted the rate of germination 0, while the highest (3.85 M= n1/t1 + n2/t2 ...+n x/ tx, seeds/day) was at a temperature of 25°C. In the weedy sunflowers highest germination was at a temperature where M is germination rate and n1, n 2 ...nx stand for the of 20°C (2.43 seeds/day) and the lowest at 25°C (0.08 number of seeds that germinated on days t1, t2 ... tx starting seeds/day. In the case of the highest rate of germination of from the beginning of imbibition (Maguire, 1962). ragweed (7.84 seeds/day) is achieved at a temperature of 30°C, while at 10°C (0 seeds/day) the rate was the lowest All data was analyzed by one-way ANOVA (F-values) (Table 3). Seeds of ragweed that were exposed to the using statistical software Statistica 5.0. Differences treatment of light/dark 16h/8h and temperature of 24°C between populations were tested using t-test. had the highest rate of germination (3.36 seeds/day),
312 Table 1. Percentage of germinated seeds of wild oat, common cocklebur, weedy sunflower and ragweed at different temperatures on the seven day of the experiment
Percent of germination Temperature (°C) Wild oat Common cocklebur Weedy sunflower Ragweed 10 90.00±8.94 0.00±0.00 30.0±8.16 0.00±0.00 15 85.62±13.15 36.67±5.77 32.5±9.57 13.54±5.37 20 73.75±14.55 36.51±23.09 35.0±1.0 26.87±9.46 25 70.62±18.06 43.33±5.77 40.0±0.0 30.0±6.44 30 8.75±2.04 36.67±23.09 5.0±0.82 23.33±6.21 35 6.87±7.93 36.67±23.09 5.0±1.0 18.12±6.43
Table 2. Statistically significant differences in germination (%) in wild oat, common cocklebur, weedy sunflower and ragweed at different temperatures (t-test) T(°C) 10 15 20 25 30 10 15 20 25 30 Wild oat Common cocklebur 15 ns ** 20 ** * ** ns 25 ** * ns ** ** ns 30 ** ** ** ** ** ns ns ns 35 ** ** ** ** ns ** ns ns ns ns Weedy sunflower Ragweed 15 ns ** 20 ns ns ** ** 25 * ns ns ** ** ns 30 ** ** ** ** ** ** ns ** 35 ** ** ** ** ns ** * ** ** * p<0,001**, 0.01
Table 3. The influence of different temperatures on germination rate of wild oat, common cocklebur, weedy sunflower and ragweed Germination rate Temperature (°C) Wild oat Common cocklebur Weedy sunflower Ragweed 10 5.66±1.72 0.00±0.00 0.59±0.22 0.00±0.00 15 7.75±1.46 2.70±0.30 1.73±0.91 1.15±0.47 20 7.88±1.68 2.15±0.15 2.43±0.74 5.12±2.26 25 7.90±2.00 3.85±0.22 0.08±0.15 6.67±1.57 30 0.79±0.19 3.54±0.11 0.67±0.2 7.84±2.21 35 1.12±0.30 2.90±0.30 0.79±0.1 5.86±1.92 while the lowest germination had the seed that was species except for weedy sunflower, in most cases, there sprouted in darkness and at constant temperature of is a significant difference (p<0.01) in germination rate 22°C (1.11 seeds/day). The results show that for all at various temperatures (Table 4).
313 Table 4. The significance of differences in the rate of germination of wild oat, common cocklebur, weedy sunflower and ragweed at different temperatures (t-test). T(°C) 10 15 20 25 30 10 15 20 25 30 Wild oat Common cocklebur 15 ** ** 20 ** ns ** ** 25 ** ns ns ** ** ** 30 ** ** ** ** ** ** ** ** 35 ** ** ** ** ns ** ns ** ** ** Weedy sunflower Ragweed 15 ns ** 20 ** ns ** ** 25 ns * ** ** ** * 30 ns ns ns ns ** ** ** ns 35 ns ns ns ns ns ** ** ns ns * p<0,001**,0.01
Disscusion rate of germination. Also Jovičić et al. (2011) concluded that the optimum temperature for germination of weedy The results indicate that wild oat seed germinates sunflower is 25-30ºC. better at lower and ragweed, weedy sunflower and Ragweed was germinated in a smaller percentage of common cocklebur seeds at higher temperatures, which seeds at most favored temperature of 25°C. One of the was expected given that these three species belong to the possible reasons for poor germination ragweed is that it is group of late spring, and a group of wild oats of early characterized by a very strong seed dormancy (Williemsen spring weeds. and Rice, 1972), but also that the seed was sprouted in Knowing the optimum temperature for germination the dark. In the following experiments to determine of oats as weeds in small grains is of great importance the seeds of this species germinate better in the light of because of better forecast time for germination and which coincided with the results of Ristic et al. (2008). sprout. Stougaard and Xue (2004) have confirmed that Our study agrees with the observations of Sermons the reduction in wheat yield due to competition with wild et al. (2008), that the temperature effects on seed oat of moving from 47 to 58%. The our study confirmed germination. The results indicate the existence of that oats germinate best at a low temperature of 10°C significant statistical difference between germination and the lowest seed germination had a temperature of at different temperatures. Only the results at % of 35°C. The effect of temperature on the process of seed germination of common cocklebur and weedy sunflower germination of A. fatua and A. ludoviciana, investigated germination rate was not statistically significant. These by Fernandez-Quinantila et al. (1990), where they got results are important, because a better understanding an opposite observation that the germination of seeds of of the biological properties of the seed (of viability, A. fatua at temperatures lower than 10°C is worse, and germination, periodic germination and dormancy) at temperatures above 20°C better. Seeds of common can be useful for predicting the spread of weeds, their cocklebur showed the highest % germination and invasiveness and the development of more effective germination rate at 25°C. Norsworthy & Oliveira (2007) strategies to control weeds in arable and on non- concluded that the optimal temperature in field trials agricultural areas. for seed germination of common cocklebur is 35 and 40°C. Based on the daily readings of seed germination of weedy sunflower, germination rates were calculated to Acknowledgement indicate the dynamics of seed germination. The results showed that the germination rate is not in accordance We are grateful to the Ministry of Education, Science with established % of seed germination. Namely, at a and Technology of Republic of Serbia for support in this temperature of 25°C, the highest % of germination was investigation (Project III46008), COST Action SMARTER recorded, and also at the same temperature, the lowest (FA1203) and EU FP7-REGPOT-AREA Project.
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