Germination is a key process in plants' phenological cycles. Accelerating this process could lead to improvment of the seedling growth as well as the cultivation efficiency. To achieve this, the effect of microwave frequency on the germination of rice seeds was examined. The physiological feedbacks of the MR 219 rice variety in terms of seed germination rate (GR), germination percentage (GP), and mean germination time (MGT) were analyzed by exposing its seeds to 2450 MHz of microwave frequency for one, four, seven, and ten hours. It was revealed that exposing the seeds to the microwave frequency for 10 hours resulted in the highest GP. This treatment led to 100% of germination after three days with a mean germination time of 2.1 days. Although the other exposure times of microwave frequency caused the moderate effects on germination with a
Rice (
The rice seeds belonging to MR 219 variety were provided by Universiti Putra Malaysia.
A 108.5 mm screw mount dipole antenna (GW.15.2113, 1.58 mW) along with a frequency control oscillator (ZX95-2490 model) including the linear tuning characteristics such as frequency range of 2280–2490 MHz, low phase noise, low pushing and low pulling was exploited in this study. The applied amplifier (Model ZX60-3011) was a 50 Ω, 400 to 3000 MHz low noise. The other features were high dynamic range, wide bandwidth, low noise figure
The present study was divided to two separate experiments, which was carried out throughout October to December 2012. The first experiment was all about testing different exposure times, which was designed based on Randomized Complete Block Design (RCBD) with five treatments (five different exposure times of microwave frequency) in three replicates to find out the appropriate exposure time of microwave frequency. The treatments were included as C (control), T1 (one hour), T2 (4 hours), T3 (7 hours), and T4 (10 hours). The seeds were sterilized with 10% sodium hypochlorite (NaClO) solution for 10 minutes [
The second experiment was designed according to the first experiment’s results, in which the best exposure time (10 hours) was tested further by using different periods. This part of the experiment was also carried out based on Randomized Complete Block Design (RCBD) but, as was mentioned, only using the ten-hour treatment with three replicates.
The treatments were included at different periods of the ten-hour microwave frequency exposure comprising C (control), the first day of soaking (T10), the first two days (T20), the first three days (T30), the first four days (T40), the first five days (T50), the last day only (T01), the last two days (T02), the last three days (T03), the last four days (T04), and the last five days (T05). The seed germination conditions were the same as the first experiment.
The experiments have been done at 2450 MHz frequency and 1.58 mW energy power [
Initially, the raw data were tested for normality using the SAS software version 9.2 and the main data were then analyzed using analysis of variance and Duncan’s multiple range test in 1% level.
Putting different exposure times of microwave frequency to use prior to seed germination significantly accelerated the germination of the rice seeds. Variance analysis of the treatment effects on the measured characteristics (
Variance analysis of the different exposure times of microwave frequency effects on the measured traits in MR 219 rice variety.
Source | df | Mean square | |||||
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GPa2 | GPa3 | MGTa3 | GRa3 | RLa6 | SLa6 | ||
R | 2 | 51.67ns | 5.00ns | 0.004ns | 17.64ns | 0.002ns | 0.006ns |
T | 4 | 219.17** | 27.50* | 0.013** | 82.29** | 1.287** | 0.053** |
Error | 8 | 14.17 | 5.00 | 0.002 | 3.75 | 0.007 | 0.004 |
CV% | 19.50 | 5.21 | 0.09 | 5.49 | 0.16 | 0.22 |
Seed germination of MR 219 rice variety under different times of microwave frequency treatments. (a) Germination percentage after two days of treatment, (b) germination percentage after three days of treatment, (c) germination rate after three days, and (d) mean germination time after three days. Mean values ± SE are from three independent replicates, and values superscripted by different letters are significantly different by Duncan’s multiple range test (
Exposing the seeds to microwave frequency for ten hours improved the germination rate as shown by the
The effects of different exposure times of microwave frequency on primary shoot and root length in MR 219 rice seedlings.
The effect of exposure times of microwave frequency on the water’s temperature around the seeds inside the Petri dishes. Vertical bars represent the standard error of mean for three samples, and values superscripted by different letters are significantly different by Duncan’s multiple range test (
The microwave frequency affected the seed germination of MR 219 rice variety after treating the seeds at different days of soaking with considerable changes in GP, GR, MGT, SL, and RL. Variation due to microwave frequency in all studied traits was highly significant (
The effects of microwave frequency on the studied characteristics in MR 219 rice variety.
Treatment | TGPa2 | TGPa3 | MGTa3 | GRa3 | RLa6 | SLa6 |
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C |
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T03 |
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T04 |
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T05 |
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T10 |
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T20 |
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T30 |
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T40 |
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T50 |
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GPa2: germination percentage after two days, GPa3: germination percentage after three days, MGTa3: mean germination time after three days, GRa3: germination rate after three days, Sla6: shoot length after six days, and RLa6: root length after six days. Different letters indicate a significant difference between the values of pairs of accessions within columns (Duncan’s multiple comparison test,
The mean of
The effect of different periods of microwave frequency on shoot and root length in MR 219 rice variety. (a) Root length after six days and (b) shoot length after six days. Mean values ± SE are from three independent replicates, and values superscripted by different letters are significantly different by Duncan’s multiple range test (
The propagation of rice generally occurs through seeds or seedlings, and seed germination depends on seed structures and environmental factors that affect the growth potential of embryo [
Therefore it can enhance the movement of molecules and improve the growth potential of the embryo. Our results matched up well with the findings of Nelson [
According to the results of the present study, exposing the seeds to the ten-hour microwave frequency at the first day of soaking was very important in improving the seed germination percentage and rate. The energy content of the used microwave frequency facilitated the movement of water molecules and perhaps increased the water absorbance by the embryo of the MR 219 rice seeds, and this can be justified by the enhancement in the measured traits such as GP and GR. Unlike these two traits (GP and GR), applying the ten-hour treatment of microwave frequency in the first three days was not efficient enough in improving RL and SL due to the lack of germinated seeds in this stage. In contrast, exposing the germinated seeds during the last three days significantly affected the RL and SL and successfully led to obtain the highest RL and SL values.
Baskin and Baskin [
In spite of the interesting results achieved in the current study, we believe that this type of researches should not be limited to the germination stage. For instance, the parallel examination on maize has already revealed the positive impact of microwaves at 945 MHz on germination, growth rate, and absorbance efficiency of photosynthetic pigments [
The most effective impacts of microwave energy on the seed germination, shoot and root growth appeared after ten hours of exposure time in the period of five days. However, the mechanisms of the microwave frequencies on germination and plant growth are unknown, but, according to the positive effects of the microwave frequencies on germination indices and shoot and root growth, this technique is expected to benefit the seed germination considering its simplicity and efficiency. Another advantage of this system is improving the seed germination without causing any serious environmental toxicity for producing rice seedlings, which is the central step prior to rice cultivation. Nevertheless, none of these advantages should lead us to a negligence of any probable disadvantage of the technique.
The authors of the paper declare that they do not have any direct financial relation with the commercial identities mentioned in the present paper that might lead to a conflict of interests for any of the authors.
The authors thank Long-term Research Grant Scheme (LRGS), Ministry of Higher Education, Malaysia, for the financial support.