Experiment on the effect of pH on seed germination and plant growth

Experiment on the effect of pH on seed germination and plant growth

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ABSTRACT

The pH is the hydrogen ions concentration in the moisture provided. It defines the alkalinity or acidity of a solution. The method required us to form solutions with different pH levels and adding them to different samples of dry seeds for observation. We predicted that there would be a decreased germination rate at low pH values. We measured seedling heights in the created samples and recorded our observations after four, seven, and seventeen days. Cell 4 recorded no germination, whereas cell 2 had cell 3 had partial cell germinations. After seven days, the seed germinations improved significantly for all cells. As time increased, the height of the plants at low acidic regions that is, at pH 4 and 6, increased significantly. Although other factors affected the outcome, such as color, the maximum number of seeds germinated at these pH values. We conclude that the objectives of the experiment were achieved, and our hypothesis was validated.

INTRODUCTION

Seed germination is affected by the presence of sunlight, Oxygen, pH level, and moisture. Other factors that could affect germination are soil depth, presence of pathogens, and temperature conditions. Enough moisture assists in softening dried seeds to aid cellular metabolism before the germination can begin. The germination process requires Oxygen, which helps in the germination rate. In areas where floods occur, the soil content allows only very little Oxygen; hence plants barely grow. Aquatic plants, however, are adaptive to these conditions (Schwember,2009). Germination rates are also influenced by the temperature conditions whereby some plants thrive well in low temperatures while most require optimum temperatures of around 25 degrees Celsius.

In the presence of sunlight, plants manufacture their food (Turner et al.,1988). They require sunlight to form chlorophyll, which is a green coloring matter found in plants. If plants germinate in inadequate sunlight, they tend to be yellowish because the chloroplasts do not form hence unable to produce enough chlorophyll responsible for the green color in plants. Lack of essential minerals required by the chloroplast is also evident when plants discolor and become yellow.

In this lab experiment, the main objective was to test the effect of pH on germination and growth of seeds. The method required us to form solutions with different pH levels and adding them to different samples of dry seeds for observation. We measured seedling heights in the created samples and recorded our observations after four, seven, and seventeen days. We hypothesized that the lower the pH, the shorter the height of the plant. In that period, we also observed the number of germinated seeds and the colors of germinated plants.

MATERIALS AND METHODS

Dried seeds, cells labeled 1,2,3 and 4, alkaline and acidic pH treatments marked 2,4,6,7,8,10 and 12, measuring ruler, Litmus paper testers, test tubes, labels and markers

We selected healthy seeds and put four seed in the cells labelled 1,2,3 and 4. We repeated the procedure for another six times so that we had seven cells for each label and a total of 28 labeled cells.

Using clean pipettes, we added a drop of the pH mixture labeled 2 to cell 1. We repeated the procedure and added the rest of the pH mixtures differently to all other cells labeled 1.

We repeated the procedure above for the remaining cells until all the 28 cells were completed. We covered the cells with tape and moved them to the nearby window for sunlight exposure. We observed the germination, color of plants and measured the height of germinated plants after several 4 days

We reapplied the pH mixtures once a week to the respective cells. We recorded the results and observations at 4 days,7 days and 17 days as shown in the results.

RESULTS

Table 1 shows the observations, 4 days after planting

Table 2 shows the observations ,7 days after planting

Table 3 shows the observations,17 days after planting

From the results in table 1, there was germination in all cell 1, although not all the seed had germinated within the four days. Cell 4 recorded no germination, whereas cell 2 had cell 3 had partial cell germinations. After 7 days the seed germinations improved greatly for all cells with cell 4 showing germination in some of its cells. Height measurements were easier to take after 7 days compared to at 4 days. Color change was observed as either green or yellow for all germinated plants. In the 17 days period all the seedlings in different cells at pH 2 had died. Cell 4 recorded the least germination in all pH levels.

DISCUSSION AND CONCLUSION

Seed germination is greatly affected by the pH of the solution in which they germinate. In our experiment the pH 7 which is neutral acted as the control experiment. The solution used was distilled water level acted as the independent variable that we checked for each particular cell. The standardized and controlled variables that were varied for each cell were, seed type, amount of water/solution, amount of light and environment.

We used seeds of the same plants for uniformity in maturity time to germination. Amount of water/solution. The amount of solution added was measured in equal drops added using a clean pipette. Cell trays were placed next to the window for sunlight exposure. environment was controlled by ensuring the sand used was sterilized and the depth at which the seeds were placed was equal in all cells. Precautions were taken to clean the pipette before adding pH mixture solution to any cell to avoid contamination.

From our results, germination in four days recorded a small increase in height in cells with pH values pH 2, 4 8,10 and 12. the solutions were at this time strongly acidic and strongly alkaline. Cells at pH 6 recorded the maximum height increase because they were less acidic hence, they were favorable media for seed metabolism and growth. Strong alkaline precipitate minerals necessary for growth hence they also record germination of seeds with low heights.  Plants that received maximum sunlight were green in color but those further away from the window were yellow because they could not receive enough sunlight. Cell 4 was used as the negative control for our experiment.it showed no growth in all cells at all Ph levels.

As time increased the height of the plants at low acidic regions that is, at pH 4 and 6 increased significantly. Although other factors affected the outcome such as color, maximum number of seeds germinated at these pH values (Schwember,2009). .

In conclusion our hypothesis that the lower the Ph the shorter the plant holds for the experiment. This means that acidic soils inhibit lateral growth of plants. A real case scenario is observed in acidic rain. Areas experiencing such rain usually have low vegetation with retardedly growing plants

REFERENCES

Schwember, A. R. (2009). Genetic analyses of priming and aging in lettuce (Lactuca sativa L.) seeds and the effect of Oxygen on seed longevity.

Sushma. (2009). Effect of seed storage on oil content and seed germination of jatropha curcas linn.

Turner, Gregory & Lau, Robyne & Young, Donald. (1988). Effect of Acidity on Germination and Seedling Growth of Paulownia tomentosa. The Journal of Applied Ecology. 25. 561. 10.2307/2403844.