Abstract
Salinity of a solution has marked influence on the germination of seeds. In this view, the study hypothesized that the rate of germination decreases as the concentration KCl reduces. To establish the impact of salinity on germination of mung seeds, the study employed distilled water and increasing concentrations KCl, namely, 0.1M, 0.25M, 0.40M, and 0.50M, as a source of water that seeds imbibe to germinate. The findings showed that seeds placed in distilled water germinated at a higher rate than the seeds placed in increasing concentrations of KCl.
Moreover, the findings showed that seeds placed in different concentrations of KCl exhibited decreasing rate of germination as concentration of KCl increases. Evidently, 100% of seed placed in distilled water and 0.10M KCl germinated within a period of one week, while seeds placed in 0.25M, 0.40M, and 0.50M KCl exhibited the germination rate of 73.3%, 32.5%, and 3.3% respectively. Hence, the findings support the hypothesis that the rate of germination of mung beans decreases as the concentration of KCl increases.
Introduction
Germination of seeds is subject to many conditions of the environment such as the degree of moisture, warmth, oxygen, and salt concentrations amongst other factors. Germination is an important cycle of a plant growth because it entails springing of a seedling from a dormant seed, which stores nutrients. The presence or absence of the necessary conditions dictates the germination of a seed and formation of a seedling.
In this case, salinity is a significant factor that slows down the germination of a seed because it creates physiological drought. Bojovic, Delic, Topuzovic, and Stankovic state that inorganic ions such as Na+, Cl–, and K+ inhibit germination of seeds and growth of plants because they reduce the osmotic potential of plant cells (83). The statement implies that high concentration of salts reduces the osmotic potential of seeds during their germination, and thus, slows or inhibits germination.
Abari, Nasr, Hojjati, and Bayat explain that the osmotic potential of a seed reduces as concentration of salt in its environment increases (53). In essence, salt solution creates an osmotic gradient, which prevent seeds from absorbing water from their environment via osmosis. Fundamentally, in this case, osmosis is the flow of water molecules from a region that has a low concentration of salts to a region that has a high concentration of salts.
The effects of salt concentration on germination vary according to the nature of seed and type of salt concentration. Some plants are tolerant to high concentration of salts, while other plants are unable to tolerate even the lowest concentration of salts. Moreover, some types of salts do not only reduce the osmotic potential of plants, but they cause toxicity, and hence, they inhibit germination and growth of plants significantly.
Bojovic et al. state that high concentration of salts affect the absorption of water and nutrients by plants as they cause physiological drought (83). Therefore, the objective of the study is to establish the influence of salinity on the rate of germination of mung beans. In line with the objective, the study, therefore, hypothesizes that the rate of germination of mug beans decreases as the concentration of KCl increases.
Method and Materials
The materials that were used in the experiment are 12 ml distilled water, 12 ml of each 0.10M, 0.25M, 0.40M, and 0.50M potassium chloride solutions (KCl), 50 mung bean seeds, 10 paper towels, and 5 plastic bags. Firstly, two paper towels was folded together twice to make a pair of 5 folded paper towels. Secondly, 50 seeds of mung beans were separated into five portions consisting of 10 seeds each, and then each portion was placed in different paper towels.
The five folded paper towels with mung seeds folded in them were then put in separate five plastic bags. After that, each of the five folded paper towels was wetted separately with 12 ml of distilled water, 12 ml 0.1M KCl, 0.25M KCl, 0.40M KCl, and 5.0M KCl. All the five plastic bags were subsequently placed under the same conditions of temperature and light, 71.0 °F and sunny place. The germination of the seeds was checked daily for a period of one week and the number of germinated seeds was counted each day. The rate of germination was then calculated and presented in a table and graphs.
Results
The table 1 below and graphs indicated, figure 1 and 2, present the findings of the study. Table 1 presents summary of findings because it shows the percentages of mung beans, which germinate in each day from the first day to the seventh day. What is common is that none of the seeds germinated in the first day. During the second day, 41.1%, 40%, 2%, 0%, and 0% of seeds germinated in distilled water, 0.10M, 0.25M, 0.40M, and 0.50M of KCl respectively. On the third day, some of the seeds germinated in all towels except the towel that had 0.50M KCl. The summary table also indicates that all the seeds in the control (H2O) germinated by the fifth day, while all seeds in 0.10M KCl germinated by the seventh day. However, not all seeds in 0.25M KCl, 0.40M KCl, and 0.50M KCl germinated by the end of the seventh day. Essentially, the rate of germination of seeds decreased with an increase in the concentration of KCl.
Table 1. Summary of Findings.
The table above summarizes the findings of study by showing the rate of germination in terms of percentages in seeds grown in distilled water and increasing concentration of KCl.
The graph below (figure 1) shows that the rate of germination of seeds in distilled water increases with time in that all the seeds germinated by the fifth day.
The figure 2 above is a graph that shows that the rate of germination of seeds decreases with an increase in the concentrations of KCl. The graph shows that all seeds placed in distilled water germinated by the fifth day, while all the seeds placed in 0.10M KCl germinated by the seventh day. However, seeds placed in 0.25M KCl, 0.40M KCl, and 0.50M KCl exhibited germination rate of 73.3%, 32.5%, and 3.3% respectively, as depicted in the graph below.
Discussion
The table 1, which presents the summary of the results, illustrates that the rate of germination of seeds increases as the concentration of KCl decreases. From the table, it is quite evident the seeds placed in the distilled water germinated faster than the seeds placed in increasing concentrations of KCl. Manz, Muller, Kucera, Volke, and Leubner-Metzger explain that seeds imbibes water easily and germinate faster when water has no dissolved salts (1538).
Fundamentally, the distilled water does not reduce the osmotic potential of the seeds, and hence, seeds can absorb water through osmosis (Demir and Mavi 900). In this case, seeds placed in distilled water absorbed water quite easily and utilized them in their biochemical processes that are essential for the germination of seeds. Thus, the absence of osmotic stress in the seeds placed in distilled water to germinate explains the fast rate of germination.
Figure 1 depicts the rate of germination of seeds placed in distilled water increases with time and attains the highest rate of germination after one week. The use of distilled water as the control of the experiment depicts the importance of osmosis in the germination of seeds. Plants absorb water from their environment via the osmosis mechanism since the dissolved salts in their cells have high osmotic potential than the surrounding environment, and thus, water flows into the cells via osmosis (Demir and Mavi 898). Hence, when the seeds grow in distilled water, they easily absorb water and utilize in the metabolic processes that are central in the germination of seeds.
Comparison of the effects of various concentrations of KCl indicates that seeds placed in the lowest concentration of KCl (0.10M) germinated within a period of one week and exhibited 100% rate of germination, while those placed in 0.25M, 0.40M, and 0.50M exhibited the germination rate of 73.3%, 32.5%, and 3.3% respectively. The decreasing rate of germination as concentration of KCl increases happens because KCl reduces the osmotic potential of seeds, and thus, it causes osmotic stress and makes seeds experience physiological drought.
According to Manz et al. salinity reduces the rate of germination of seeds as it creates physiological drought, which prevents seeds from absorbing water from the environment via osmosis (1541). In this case, KCl slowed down the rate of germination of the seeds because it created physiological drought and reduced the ability of the seeds to absorb water via osmosis. Analysis of the findings, therefore, supports the hypothesis that the rate of germination of mug beans decreases as the concentration of KCl increases.
Conclusion
Germination of seeds is an important cycle of plants because it leads to the emergence of seedlings, which perpetuate the existence of plants in nature. Fundamentally, germination of seeds is subject to many environmental factors such as temperature, oxygen, and salinity. In this case, the experiment proved that salinity decreases the rate of germination of mung beans. Evidently, seeds placed in distilled water have the highest germination rate because all of them germinated after a period of a week. Comparatively, germination rates of seeds placed in 0.10M, 0.25M, 0.40M, and 0.50M KCl were 100%, 73.3%, 32.5%, and 3.3% respectively after a period of one week. Hence, the study supported the hypothesis that the rate of germination of mug beans decreases as the concentration of KCl increases.
Works Cited
Abari, Akram, Mohammad Nasr, Mohammad Hojjati, and Dariush Bayat. “Salt effects on seed germination and seedling emergence of two Acacia species.” African Journal of Plant Science 5.1 (2011): 52-56. Web.
Bojovic, Biljana, Gorica Delic, Marina Topuzovic, and Milan Stankovic. “Effects of NaCl on seed germination in some species from families Brassicacea and Solanaceae.” Kragujavac Journal Science 32.1 (2010): 83-87. Web.
Demir, Ibrahim and Kazim Mavi. “Effect of salt and osmotic stresses on the germination of pepper seeds of different maturation stages.” Brazilian Archives of Biology and Technology 51.5 (2008): 897-902. Web.
Manz, Bertram, Kerstin Muller, Birgit Kucera, Frank Volke, and Gerhard Leubner-Metzger. “Water uptake and distribution in germinating tobacco seeds investigated in vivo by nuclear magnetic resonance imaging.” Plant Physiology 138.1 (2005): 1538-1551. Web.