Germination is the process by which a plant develops from a seed and grows in optimal conditions where temperature and water available is suitable for the transformation of a seed into a plant. The conditions are favorable when the right balance of air, moisture and temperature are reached that stimulate the seed to come out of hibernation and start sprouting a root and shoot that starts the process of germination(Bewley, J. Derek, et al). Mostly, germination is the growth of embryonic seeds. When a seed is germinating and fertilizing, it produces an embryo where an embryo is present after fertilization and this embryo gets its nutrients from the cotyledon and is wrapped in a seed coat. Cotyledon is the first leaf and it is the fleshy part of a seed. As the seed germinates, cotyledon provides important nutrients to embryo along with root and shoots system. The root system grows downward and anchors the plant in the soil, and absorbs water and nutrients and stores them. The shoot system grows upwards usually above the ground and it has many functions such as photosynthesis, reproduction, and food and water conduction. Germination is a complex process and it gets affected by many environmental factors such as weather, temperature, moisture and ventilation. Other factors that can potentially impact germination include pH, caffeine, fertilizer, and microwaves. Shimomura (1990) has confirmed experimentally that radish seeds germinate and grow rapidlyby using ultrasonic irradiation.
Part of this experiment includes studying how germinating Raphanus savitus can be affected by the pH of the environment and how they respond to the effect of a weak acid and a strong acid, a weak base and a strong base. Stubbendieck (1974) stated that slightly acidic levels of pH 5.5 and 6.0 had the highest percentage of successful germination occur. Rain is the one of the environmental factors that affects plants according to Wan and Yaohu (2006). Normally, rain is slightly acidic because it has carbonic acid. The slightly acidic rain makes the seed coat weak and allows the seed to germinate rapidly. However at pH 2.5 which is strongly acidic, the seed had lowest germination because it causes shoot and root of seedlings to decay which makes it very hard for the seedlings to emerge (Fan and Wang 2000). With strong basic solutions, there was the same problem as strongly acidic solutions which makes the plants fail to germinate or give them a low chance to germinate (Reichert et al. 1980).
We hypothesize that the presence of caffeine may also stimulate the growth of the seeds since previous literature suggests that caffeine may have a positive impact on the process of germination. Ransom (1912) stated that small doses of caffeine stimulates and increases activity of germination and growth. We decided to study the effect of varying concentrations of caffeine on seed growth with the hypothesis that a small concentration of caffeine will increase seed growth.
Fertilizer is one of the simplest treatment groups that we expected to have a positive impact on seed growth. Al-Mudaris (1999) concluded fertilizer treated seed had higher germination percentages than untreated seeds. All of seeds with fertilizer treatment germinated faster than untreated seeds because the fertilizer provides nutrients that a seed needs to germinate (Maxton, 1927).
Ragha (2011) described how microwave effected on germinating seeds. The seeds that were microwaved for the short period of time germinated early than normal seeds. However, the seeds that were microwaved longer period of time did not germinate. The seeds with shorter intervals of microwave treatments germinated faster than normal seeds because the heat from the microwaves helped to open up the seed coat. On the other hand, the longer microwave treatments caused the seeds to become overheated and get damaged. Therefore, the germination did not occur.
Agriculturists are still trying to study the most suitable conditions for the seed to germinate. This question has been raised for several centuries and is being studied even today because optimizing germination conditions can have a huge impact on crop productivity and efficiency in the field of agriculture. It will have an enormous impact on the way food is produced if the stages of germination can be optimized by manipulating the environment. As the results shown below will reveal, this experiment can add to our knowledge about the effects of different environmental factors on plant seed germination. While performing this experiment, the negative and positive effects of the environmental factors on Raphanus savitus seed germination can be shown as well as the favorable conditions for the seed to sprout. This study will increase our knowledge of germinating seeds of Raphanus savitus. Therefore, we will study how germination is affected under treatments such as different pH, caffeine, fertilizers, and microwaves.
Materials and Methods
The radish seeds (Raphanus savitus) were subjected to different pH solutions of caffeine, fertilizers and microwave treatments. For microwave treatments the first step was to label the Petri dishes as follows - 0 seconds, 30 seconds, 1 minute, 3 minutes, and 5 minutes. Make two sets of Petri dishes for each treatment. Place 10 seeds on filter paper in each Petri dish. Fill a beaker with 100 ml of cold water and place in microwave with petri dishes. The water beaker will absorb any excess energy. Set the timer on high for 30 seconds then start the microwave. After microwaving the seeds add 2 ml of deionized water to filter paper, seal the dishes with Parafilm. Dump water in beaker and replace with cold water for next treatment time. This procedure was repeated for 1 minute, 3 minutes and 5 minute treatment times.
For caffeine group, four different concentrations were tested: 0.15625M, 0.003M, 0.00625M, and 0.125M. For pH group, five different pH treatments were used - 2, 5, 7, 9 and 14. For the fertilizer - 1.25g/250mL, 2.5g/250mL, 5g/250mL, 10g/250mL were the concentrations tested. Using a pipette, 4mL of each prepared solution were added to two sets of Petri dishes per treatment. For those dishes with 0 seconds in the microwave, no caffeine, 0g/250 ml fertilizer and pH of 7, add 4mL of deionized water instead. A total of 40 Petri dishes for the treatments were used. Place all of the dishes on the counter for two weeks and be sure they are all sealed and labeled with the appropriate treatment. After two weeks, measure the root length of each germinated seeds using a ruler and record in millimeters for each seed. If there is no germinated seeds record as zero millimeters. Make sure you are wearing gloves before you measure the pH groups. After measuring all the root of seeds, all materials can be disposed.
An ANOVA analysis was conducted on the root lengths of the seeds per treatment category including fertilizer, pH, caffeine and microwave treatments. F values were calculated and a P value of <0.05 was considered to be statistically significant. The mean, minimum and maximum values of the root length were calculated for the treatment groups at the varying concentrations of pH, fertilizer and caffeine and the different treatment times for the microwave treatments.
Results showed that not all of the treatment conditions had the same effect on root growth. Most treatments had a negative effect on root growth whereas only the microwave treatments had a positive effect. In the fertilizer treatment, average root lengths of radish seeds were 15.26mm and the maximum root length was 140mm (Table 1). The root length of radish seeds that were not treated with fertilizer treatment group showed average of 31.15mm which was highest. The lowest root length of radish seed was 1.65 with 10g fertilizer treated group (Figure 1). The effect of fertilizer treatments on germination of radish seeds is negatively significant (P value 2×10-16) (Table 1).
Figure 1: This figure indicates fertilizer effects on growth of Raphanus sativus.
In pH treatment, the average root length of radish seeds were 6.19 mm and maximum root length was 101 mm. The highest germination was seen in pH 7 (neutral water) with average 30.77 mm of root length. The lowest germination was seen in pH 14 with average 0.0025mm of root length (Figure 2). The effect of pH on germination is negatively significant with a P value of 2×10-16 (Table 1).
Figure 2: The figure indicates different pH treatment effect on growth of Raphanus sativus. The y axis shows mean root length in mm and the x axis has each treatment category according to the different pH measurements of the solutions with the root length shown underneath.
In different concentration of caffeine treatment, the average root lengths of seeds were 11.9 mm, and the maximum was 370 mm. (Table 1). The highest germination occurred when there was no caffeine, while with the 0.125M of caffeine concentration, it showed lowest germination (Figure 3). The effect of caffeine treatment on germination seeds is negatively significant ( P value 2×10-16) (Table 1).
Figure 3: The figure indicates different concentration of caffeine effect on growth of Raphanus sativus. The root length in mm is on the y axis and the x axis has different bars according to the different concentrations of caffeine used. As can be seen, the 0M caffeine solution had the highest root length and all other concentrations had much lower root length measurements.
In the microwave treatment, the average root length of radish seed was 38.66mm and maximum root length was 150mm (Table 1). The lowest growth was seen in the 0 sec heated group with an average of 35.61 mm root length. On the other hand, all of the heated seeds showed higher growth. The highest growth was observed in the 180sec heated group in microwave with a mean root length of 42.15 mm (Figure 4). The different periods of time of microwave effect on germination seeds are positively significant (P value 0.243).
Figure 4: The figure shows that different period time of microwave treatment effect on growth of Raphanus sativus. The y axis shows root length in mm and the x axis shows the different bars representing the microwave heating times for each group of seeds and the corresponding root length. Each group correlated with an increase in root length as compared to the no treatment group.
The result indicated that all of the different treatments had an effect on the seed germination. The microwave treatment had the only positive effect on seed germination. On the other hand, fertilizer, pH, and caffeine showed negative effect on growth of seed.
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