The Mutational Effect of Radiation on the Growth of Corn (Zea mays)

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The Mutational Effect of Radiation on the Growth of Corn (Zea mays)1

ABSTRACT

The effect of varied doses radiation was tested on the growth of Zea mays. The study used four treatments of corn seeds – control (0 krad), 10 krad, 30 krad, and 50 krad. For at most three days a week, the height of the corn was measured and recorded. The growth of the 10 krad treatment showed great similarity with that of the control while the 50 krad treatment barely sprouted. Thus, the higher the dose of radiation the more damage it can cause on the growth of the plant.

INTRODUCTION

Evolution is said to be the consequence of genetic variation of the original gene pool of a population. Genetic variation can be introduced in a gene pool through a random or permanent mutation (Solomon & Berg, 1995).

Mutation is a process that causes alteration in the base pair sequence of a DNA molecule. It can occur at a base-pair level or at whole segments of chromosomes (Russell, 2000). These changes can greatly affect the phenotype— physical appearance and metabolic processes of an organism. Mutation can occur by either of the two means – spontaneous mutation or induced mutations. Spontaneous mutation takes place when the change in the DNA structure is a consequence of irregularities in biological processes. Induced mutation, on the other hand, are DNA alterations caused by an external or environmental factor (Brooker, 1999).

One factor that can induce mutation is radiation. The dictionary defines radiation as a wave of energy that can travel through space and charge matter particles. The general effect of radiation on a cell is that it excites the present molecules making it highly reactive. These excited particles scatter away from areas of high concentration and react with other particles around it. When these highly charged molecules react with DNA, it can cause damage that can lead to mutation (King, 1962). Inducing mutation through radiation had been compared with shooting a target in the dark in Dr. E. C. Colin’s book. Mutational effects radiation are said to be unpredictable because there is no way to be certain if the radiation will cause damage to the DNA.

In this study, radiation was used to cause mutation in Zea mays. Corn seeds were subjected to varying doses of radiation – 0 krad (control), 10 krad, 30 krad, and 50 krad. The seeds were then planted and their growth were observed and recorded.

It is expected that the higher the dosage of radiation the plant was subjected under, the greater effect it will have on its growth. Higher radiation dosage can cause a more extensive damage on the DNA of the organism compared to lower doses.

This study is aimed to determine the effects of radiation caused mutation on the growth of the plant are to be determined through this experiment Zea mays (Corn). The specific objectives are

  1. To identify the general effect of radiation on the growth of Zea mays; and
  2. To determine the different effect of varied doses of radiation on the growth of Zea mays.

MATERIALS AND METHODS

Mutation was introduced to corn seeds through irradiation. There were four treatments used for the experiment and each of these treatments had a set of ten seeds. Three of the four treatments were subjected under varying doses of radiation— 10 krad, 30 krad and 50 krad respectively while another was not subjected to radiation and was set to be the control of the experiment.

The seeds were then planted in a designated plot for the class. Each plot had four rows; one row for every treatment and labeled accordingly. In a single row, ten seeds of the same treatment were planted with at least five centimeters distance from each other. The growth of the plant was then observed and recorded, for at most three times a week for 46 days.

RESULTS AND DISCUSSION

The average growth of the plant in day’s interval can be seen in Table 1. The growth in height of the plants, true to most treatments, has a usual increasing trend aside from days 25 to 29 in the 30 krad plants which had a decrease in height, and in the 50 krad plant where at day 15 had a plant had a sprout but it was no longer observed at day 18. The observed discrepancies can be attributed to measuring errors or other factors such as presence of herbivores that may have feed on the plant, causing alteration on the plants’ height or other factors that may have led to uprooting.

Figure 1 shows the growth of the plants in contrast to the other treatments. It can be gathered from the graph that the 10 krad plants have a very close growth rate with that of the control. The growths of the 30 krad plants are significantly slower than that of the control and the growth of the 50 krad is close to non-existent or non-significant.

The general trend that can be observed from the data is that the lower the dosage of radiation applied to the seed the lesser effect it had on its growth. As discussed earlier in the introduction, radiation causes an excitement in the molecules of a cell. The lower the radiation applied on the seed, the less likely it is cause any damage on the DNA because there are lower chances of any ionized particles to react with the DNA. For plants with 50 krad, they exhibit little to no growth at all. It is because the high amount of radiation has led to large amounts of excited molecules, greatly increasing the chances of damaging of DNA. This then lead to slowing or stopping the growth of 50 krad plants.

From the observations and the data gathered it can be concluded that the initial hypothesis is true. The hypothesis states the higher dosage of radiation introduced the greater effect it will have on the growth of Zea mays.

Table 1. Average Height of Control, 10 krad, 30 krad, and 50 krad Zea mays.

Days

Control

Control

Average Height in cm

10 krad

Average Height in cm

30 krad

Average Height in cm

50 krad

Average Height in cm

1

13.6

12.8

8

0

4

21.6

19.9

10.7

0

6

24.9

22.7

11.2

0

11

35

35.7

15.5

0

13

39.9

41.7

19.2

0

15

48.8

49.9

24.9

7.5

18

66.7

65.8

33.6

0

20

72.8

71.3

41.8

0

22

81.1

78.9

44.9

0

25

95.2

88.6

55.9

0

27

95.7

88.7

53.6

0

29

99.9

92.8

55.9

0

32

104.3

94.9

57.4

0

34

108.9

95.6

60.4

0

39

114.2

100.2

67.3

0

41

115.1

100.5

67.8

0

43

116.3

101.1

68.2

0

46

117.8

110.2

74.1

0

Figure 1. Growth of Zea mays with varying doses of radiation— 0 krad, 10 krad, 30 krad, and 50 krad.

SUMMARY AND CONCLUSION

The effect of radiation on the growth of Zea mays was determined in this experiment. Corn seeds were subjected to different amount radiation— 10 krad, 30 krad, and 50 krad, one set of corns was not subjected to any radiation and was labeled as the control for the experiment. The seed were then planted and their growth in height was recorded at day’s interval.

The result gathered showed that the growth rate of the control and the 10 krad were very close, the growth of the 30 krad was comparatively slower than the first two while the 50 krad did not grow significantly. Therefore, the 50 krad treatment have the greatest effect on the growth of the corn.

LITERATURE CITED

Brooker, R. J. (1999). Genetics: Analysis and Principles. Menlo Park: Benjamin/Cummings imprint. p. 462.

Colin, E. C. (1949). Elements of Genetics. Philadelphia: The Blakiston Company. pp. 299-300.

King, R. C. (1962). Genetics. New York: Oxford University Press. pp. 190-193.

Russell, P. J. (2000). Fundamental of Genetics. 2nd Ed. San Francisco: Benjamin/Cummings imprint. p. 409.

Solomon, E. P., & Berg, L. R. (1995). The World of Biology. Florida: Saunders College. pp. 322-323.