Abstract
This experiment compared the rate of mung seed germination when treated with two different conditions; distilled water and 0.1% potassium chloride solution. The number of mung seeds that germinated was recorded for the various solutions. The length of the shoot and root of the germinated seedlings was also measured and registered. Maximum seed germination was observed in distilled water. Potassium chloride inhibited germination (Xu 10). The initially dry seeds were first soaked in distilled water overnight before planting into the seed pots. The medium consisted of paper towels; one soaked in distilled water, and the other soaked in 0.1% potassium chloride solution. Other conditions of sunlight and temperature were kept constant. The non-germinated seeds that had been subjected to the potassium chloride condition germinated when subjected to distilled water. The result suggested that the concentration of potassium chloride of 0.1% did not cause toxicities to the seed (Xu 10). Therefore, seed viability and germination was not affected by the concentration. The experiment showed that seed germination was negatively affected by salt concentration in the medium of germination; in this case, a soaked paper towel. For optimum seed germination, a neutral medium is therefore recommended, since germination is osmotic.
Introduction
Soil ionic content is one of the major factors affecting seed germination (Yousuf 34). Other factors affecting seed germination are moisture content, optimum temperature and favorable sunlight intensity and wavelength (Yousuf 34). Many experiments previously carried out have associated high soil salinity with crop toxicity. Different chloride solutions have different effects on seed germination, whereby some chlorides are found to increase the rate of germination in one seed and inhibit the rate of germination in another. The ionic effects of the salt concentration inhibit the enzymatic processes and also the action of other ions. For example, presence of sodium ions inhibits uptake of potassium ions in halophytes. Presence of chloride ions has also been found to inhibit the uptake of nitrates. This further affects the metabolism in the seed that yields energy necessary for germination. The root and shoot length is and consequently uptake of nutrients. The presence of high ionic concentration of ions in the germination medium decreases the osmotic potential and reduces water intake, as a result. Seeds take in water through osmosis and swells up during germination (assuming the seed is initially dried) (Yousuf 34). The seed radical sprouts first, then the plumule. The radicle forms the root section while the plumule forms the shoots. The experimental results indicate that a neutrally ionic medium is necessary for germination to occur. The ionic concentrations present in the seed must be higher than that of the external surrounding to facilitate movement of water into the seed through osmosis. This occurs as a result of the higher osmotic potential created between the seed and the external environment.
The seed in its dehydrated inactive condition can withstand adverse weather conditions of temperature. The seed can survive the extremely low permafrost conditions or hot desert conditions. In a mung seed, the embryo is wrapped inside the testa. In the testa is the food necessary for the embryo. However, the food store is inactive until seed dormancy is broken when the germination conditions become favorable, and seed germination begins. During germination, the seedling must grow fast to reach the light, the new energy source before its food store runs out.
A typical bean seed begins by a rapid intake of water. This follows when favorable conditions of water, oxygen and optimum temperature are established around the seed. The seed absorbs water through the micropyle (Chakraborty 75) through osmosis. The hydrophilic substances beneath the hard seed coat attract water for the seed through a process called imbibitions. Water moves deep into the dehydrated seed through osmosis and the rate of metabolism is further increased by this intake. The metabolism starts anaerobically but soon switches to aerobic due to more energy requirements. The aerobic metabolism requires oxygen (Chakraborty 74).
Water is required for the food store by the hydrolytic enzymes to convert the insoluble food products (polysaccharides, fats and proteins) into soluble foods (glucose). The soluble foods is translocated and used in respiration in other seedling parts. The translocation medium is water and the process is highly dependent on other processes of diffusion and active transport. Presence of water in the seed also promotes secretion of germination hormones from the embryo (Chakraborty 75). We carried out a plastic bag experiment with ten seedlings each in a pot with different concentrations. In one bag, was a paper towel soaked in distilled water and a paper towel soaked in 0.1% potassium chloride solution in another bag. Mung seeds previously soaked in water overnight were then put into the pots and the number of seeds germinated within seven days after the first seed germination was recorded. The mung seeds were soaked in water overnight to reduce the time taken for the seeds germinated. Reduced germination was observed at the concentration of 0.1% potassium chloride (Chakraborty 75). The pot with the paper towel soaked in distilled water served as a control experiment (Chakraborty 75).
Method and Materials
Twenty mung seeds previously soaked in water overnight were used in this experiment. The seeds were divided into two equal portions pairs of ten seeds each. Distilled water and 0.1% potassium chloride solutions were used as the germination medium. Two identical plastic bags were also provided for this experiment. The two setups were subjected to similar environmental conditions except for the salt concentration that was varied in the two set up experiments. The seedlings were carefully washed with distilled water before and after the root measurements were taken. This was done to ensure the roots were contaminated when touched with the hands. A certain amount of potassium chloride was dissolved in distilled water to make 0.1% of the solution. The number of seeds that germinated was noted on a daily basis. The length of shoot and root sections of the germinating seeds was also measured and recorded in centimeters. The results were tabulated and analyzed as follows.
Results
A graph that displays the number of days against the number of seedlings that germinated in distilled water medium and 0.1% potassium chloride medium.
The length of seedling root planted in distilled water was averagely 6.5 cm compared to 2.7 cm of the seedlings planted in 0.1% potassium chloride.
Discussion
Germination rate decreased in the solution of potassium chloride. Root length was also shorter in the solution treated with potassium chloride solution. All the seeds planted in distilled water conditions germinated on the seventh day. The osmotic potential was higher in the solution treated with 0.1% potassium chloride that hindered nutrient and water intake (Chakraborty 70). The presence of solute elements in the water introduced an ionic imbalance in the water conditions surrounding the seeds. The existing osmotic potential existing between the seed and the water medium in normal conditions was affected negatively. Therefore, the water could not move into the seed through osmosis. The ionic effect also affected the metabolic activities in the seed. Energy conversions in the seed were affected negatively, a condition that caused the shortening in root length in the seedlings exposed to 0.1% potassium chloride (Chakraborty 74). The seeds used in this experiment were assumed to be identical. General ill health associated with seeds while storing or deformities and differences present in seeds were taken into account.
Conclusion
Seed germination is affected by potassium concentration. Seeds require optimum ionic concentrations for germination. The rate of water intake relies mostly on osmosis that relies on the osmotic potential established between the seed and the surrounding medium (Yousuf 74). Water initiates the germination process by activating the enzymes responsible for the reactions that yield energy for the germinating bean seed. However, the experiment should be carried out using different concentrations of potassium chloride to determine the optimum conditions of potassium chloride concentration necessary for mung seed germination.
Works cited
Chakraborty, Usha. Stress Biology. New Delhi, India: Narosa House, 2005. Print.
Subba, Rao N. S. Current Developments in Biological Nitrogen Fixation. London: E. Arnold, 1984. Print.
Xu, Jianming. Functions of Natural Organic Matter in Changing Environment. Dordrecht: Springer, 2013. Print.
Yousuf, Ali Hashim. Factors Affecting Water Uptake by Mung Bean Seeds. Print