A Study on the Effect of Gamma Radiation on Growth of Zea mays

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A Study on the Effect of Gamma Radiation on Growth of Zea mays

ABSTRACT

Mutation was hypothesizes to bring about a change in the growth rate of the plant Zea mays. It was also hypothesizes that there would be improvement in the growth rate of the plant where it would grow faster for shorter harvest time interval. The experiment was done by exposing the kernels of Zea mays to different levels of gamma radiation mainly 10krad, 30krad, and 50krad. The results shown that the 10krad exposed kernels had a higher growth rate than the other levels of gamma ray radiation and there has been a significant difference on the number of Zea mays that have survived after the experiment. It can be concluded that at certain low levels of gamma radiation, there is a significant improvement of the growth rate but higher levels of gamma radiation can be detrimental to the plants.

INTRODUCTION

Mutation has occupied a central position in genetics where it is the ultimate source of hereditary variability that makes evolution possible (Auerbach, C. 1962).

An experiment was conducted on the plant Zea mays using different levels of gamma radiation. The experiment was to determine whether the gamma exposure on the corn kernels would increase or decrease the growth rate of the plant as the level of radiation increases.

Mutation may have arisen from the gene structure existing and have been changed by a chemical or physical stimulus or an error at the time of gene replication (Auerbach, C. 1962).

The error in replication can be due to gene precursor, presence of competitive analogues of substances in gene replication, enzyme inhibitors and other biochemical situations (Auerbach, C. 1962).

One physical stimulus used would be the electromagnetic radiation which is the gamma radiation.

Electromagnetic radiation is defined as a form of energy that is transmitted through space at enormous velocities (Skoog, D. West, D Holler, F and Crouch, S. 2014).

The gamma ray refers to a high energy photon which also has the highest penetrating power of all the electromagnetic radiations (Zumdahl, S and Zumdahl, S. 2010).

There are other kinds of radiation which also brings mutation such as Neutron rays and ultraviolent rays (Muntzing, A. 1961). Muntzing (1961) also stated that ultraviolent rays had milder effects compared to X rays and gamma rays but it was believed that it was the only one that could bring true gene mutation.

It can also be hypothesized that mutation occurred as the corn kernels were subjected to the gamma rays since gamma radiation can affect the DNA of the plant.

In one experiment where X rays were used, it was found that it had a fragmenting effect on the chromosomes. A full hit on the chromosomes or chromatid led to a segment break (Mutzing, A.1961).

Mutzing (1961) also stated that the chromosomal aberrations are dependent on the radiation intensity.

Another study conducted by Majeed, A. Khan A. Ahmad, H and Muhammad, Z (2010) on Lepidium sativum L showed that the gamma rays exhibited inhibitory effects on the shoot and root length at 70 krad and 80 krad due to the reduced mitotic activity in the meristem tissues and reduced moisture in the seeds.

Majeed, A. Khan A. Ahmad, H and Muhammad, Z. (2010) also stated that radiation doses 20 Krad and 40 Krad had no significant effects on survivability of seedlings as compared to 70 Krad and 80 Krad.

This would mean that at higher levels of radiation, their woud be a decline in survival of the seeds.

In the electromagnetic spectrum, X rays were weaker that gamma rays in terms of energy. It can be concluded that gamma rays can also cause chromosomal aberrations when they are used.

MATERIALS and METHODS

The kernels Zea mays were subjected to different doses or levels of gamma radiation. The doses used were 10krad, 30krad, and 50krad. Each dose had 10 kernels of Zea mays subjected and was planted in the plot provided.

The experiment lasted for almost 3 months specifically from March 18, 2015 till May 11, 2015. The kernels were all checked at a regular interval of Monday, Wednesday and Friday to record the growth of the plant. The accumulated data was used to study the effects of gamma radiation levels on plant growth of Zea mays.

RESULTS and DISCUSSIONS

The following table summarizes the data gathered over the time span of the experiment. Table 1.1 Summarized Data of Zea mays

Collection Day

Control

(Ave.Height in cm)

10 Krad

(Ave.Height in cm)

30 Krad

(Ave.Height in cm)

50 Krad

(Ave.Height in cm)

1

0

0

0

0

4

6.9

6.4

2.1

1.7

6

7.3

10.1

0

0

8

22.7

26.9

9.1

2

11

23.5

30.1

9.1

0.9

13

28.9

34.2

10.5

0

18

39.2

43.9

13.8

0

20

48

50.5

17.1

0

22

54.3

62.1

19.5

0

25

0

0

0

4.9

27

0

0

0

4.9

29

0

0

0

4.9

32

96.3

105.4

37.4

0

34

97.4

108.3

55.5

0

36

0

0

0

0

39

114.8

120.5

59.5

0

41

116.5

122.8

62

0

43

122.4

129.3

66.8

0

46

120

126.4

68.5

0

48

123.5

131.1

69

0

50

124.1

133.9

69

0

Fig 1.1 Line graph of Average Plant Height and Day Collected

The data showed that the 10Krad had the greatest length of plants. It can be said that at low levels of gamma radiation, there would be significant increase in the growth rate.

Muntzing (1961) stated that mutation process is influenced by the intensity of the radiation where it can cause a permutation that may eventually revert back to normal conditions unless the radiation exposure is continued thus having a complete mutation.

It can be associated to the results that at low levels of radiation such as 10 Krad, the mutation was only partly effective and such that the permutation it had was easily reverted back to normal however it gave a significant change in the growth rate due to the slight changes it gave to the chromosomes.

The changes are the chromosomal aberrations or segment breaks influenced by the radiation.

The higher levels of gamma radiation had lower average plant height because at higher levels of radiation could cause damage to the seeds and would have an inhibitory effect of angiosperms such as Zea mays (Majeed, A. Khan A. Ahmad, H and Muhammad, Z. 2010).

The damage can be attributed to the fragmenting effect of gamma rays on the chromosomes (Muntzing, A. 1961) and the decrease mitotic activity in the meristematic tissues and lack of moisture (Majeed, A. Khan A. Ahmad, H and Muhammad, Z. 2010).

Auerbach (1962) stated earlier that error in replication may be also due to enzyme inhibitors and Majeed, A. Khan A. Ahmad, H and Muhammad, Z. (2010) also stated that there would be an inhibitory effect of high levels of gamma radiation.

It can be concluded that at high levels of gamma radiation exposure, the plant chromosomes are fragmented thus have an inhibitory effect on the plant making its growth rate decrease but at low levels of gamma radiation, the plant can recover from the chromosomal alterations and have a significant increase in the growth rate as a result of the mutation it has undergone.

There have been several discrepancies in the data gathered. First source of error is the missing data which was not given or was not filled in thus affecting the representation of the line graph making the identification of the trend difficult.

Second is the way the data gatherer measured the plants which may have given extreme values for the data making the analysis of the data have error.

SUMMARY and CONCLUSION

The result seen was that at high gamma radiation levels, there has been a significant decrease in the growth rate of Zea mays due to the inhibitory effect that the gamma rays induce (Majeed, A. Khan A. Ahmad, H and Muhammad, Z. 2010) However at low gamma radiation levels, Zea mays had a significant increase in its growth rate.

The results answered the stated hypothesis where the exposure to gamma radiation has an effect on the growth rate of Zea mays. At higher levels, it decreases the growth rate of the plant and at low levels; the growth rate of the plant was significantly improved.

It can be concluded that excessive or high levels of gamma radiation can significantly decrease the growth rate of Zea mays due to its inhibitory effects (Majeed, A. Khan A. Ahmad, H and Muhammad, Z. 2010) but at low levels of gamma radiation; the growth rate of Zea mays is improved due to the gamma radiation acting as a physical stimulus to the kernels of the plant (Auerbach, C. 1962).

LITERATURE CITED

Auerbach, C. 1962. Mutation: An introduction to Research on Mutagenesis Part I Methods. Oliver and Boyd LTD, Tweedale Court Edinburgh 39a Welbeck Street, London

Majeed,A. Khan A. Ahmad, H and Muhammad, Z. 2010. Gamma irradiation effect on some growth parameters of Lepidium sativum L. ARPN Journal of Agricultural and Biological Science. Volume 5.

Muntzing, A.1961. Genetics: Basic and Applied; A survey of methods and main results. Stockholm Sweden, Hallands postens Boktryckeri, Halunstad, 1967.

Skoog, D. West, D Holler, F and Crouch, S. 2014.Fundamentals of Analytical Chemistry, 9thedition. Brooks/Cole, Cengage Learning, 20 Davis Drive Belmont, CA 94002- 3098,USA

Zumdahl, S and Zumdahl, S. 2010. Chemistry 8th edition. Brooks/Cole, Cengage Learning, 20 Davis Drive Belmont, CA 94002-3098,USA

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