GREENER JOURNAL OF PHYSICS AND NATURAL SCIENCES
Submitted: 21/12/2016 Accepted: 03/01/2017 Published: 30/01/2017
Research Article (DOI: http://doi.org/10.15580/GJPNS.2017.1.122116217)
Studying the effect of Gamma Ray on Morphological and Phenotypic Properties of Corn
Mirhabibi Mohsen1, Mirzaei Mahmoud Abadi Vahid2,
Askari Mohammad Bagher*1 and Tikdari Mahdi3
1Department of Physics, Payame Noor University, PO Box 19395-3697 Tehran, Iran
2Faculty of Physics, ShahidBahonar University, P.O. Box 76175, Kerman, Iran
3Department of Physics, Khajeh Nasir Toosi University of Technology Tehran, Iran
*Corresponding Author’s E-mail: mb_askari@ yahoo. com; Tel: +989131990432
Radiations have always been environmentally important. Natural radioactive resources in soil, water, weather, and manmade resources from mining, and applying their products in industrial and army fields have resulted in exposure to ionizing radiations. Nowadays, radiological effects on plants and animals are of a critical concern. Among the remarkable radiological issues in in different species of plants is the wide range of their sensitivity to ionizing radiations. The most important radiation damages in plants can be divided into three modes, including growth inhibition, reduction in reproduction capacity, and death. The purpose of the present research is to study the effect of Gamma Ray on seedling growth and on morphological and Phenotypic properties of corn seedlings. The corn seeds (single cross 704) are radiated by Gamma Ray of 0.026 and 0.06 Mev for 24, 48, and 72 hours. The results show that radiation significantly influenced such growth features as the plant height, root length, plant weight, root weight, stem diameter, the number of ears, leaf width, ear weight, the number of seed, and the seed weight of corn. The largest amounts of the mentioned features are obtained from one-day radiation and the increase in radiation up to three days causes significant reduction in all features.
Keywords: Gamma Ray, corn, morphological properties, phenotypic properties
Population growth and the subsequent daily increase in the need for food makes it necessary to have an evolution in application of modern agricultural methods and to boost the improvement of farming situation more than before. Nuclear energy has remarkable applications in different fields one of which being agriculture. Among the most important applications of nuclear energy in agriculture are: prevention of nutrient products from germination, control and annihilation of insects, postpone in fruits ripening, increasing the maintenance time, decreasing the microbial contamination, annihilation of herbal and dietary viruses, and contributing to fruiting and mutation plan of plants like wheat, rice, and cotton. One of the methods for increasing the crop productions is to modify the new cultivars of higher qualitative/quantitative properties. To achieve this goal, it is necessary to provide a genetic diversity with desirable qualitative/quantitative properties for modifiers . Radiation, as a method for increasing yields with low energy consumption, is known as one of the most effective pre-planting methods to increase yields . As a result, applying the modern scientific methods like nuclear technology can help to increase the plant yield per unit area. Using Gamma Ray in several cases has proved a modern solution through physiological and biochemical changes (i.e. germination capacity and yield) with different results depending on the crop and its usage. Therefore, the present research aims to study the effect of treating the morphological and phytochemical properties of corn by Gamma radiation. 
MATERIALS AND METHODS
The present research was conducted by means of modified corn seeds (single cross 704) provided by Seeds and Plants Modification Institute (SPMI) in Karaj, I. R. Iran. The seeds were placed near a 241Am immersion source with 5 µCu activity. The source half-life is 458 years which emits 0.026 Mev and 0.06 Mev Gamma rays and then the seeds were planted in a greenhouse in the form of perfectly random plot with 3 treatments (24, 48, and 72 hours radiation) and 3 repetitions were carried out in order to study the effect of Gamma radiation on certain morphological properties. Finally, the growth features (e.g. plant height, root length, plant weight, root weight, stem diameter, the number of ears, leaf width, fruit weight, the number of seeds, and seed weight) were measured and the obtained data were analyzed by SAS software.
RESULTS AND DISCUSSION
There is a significant indirect relationship between the increase in radiation time and the stem height and diameter among all treatments in flowering stage; in other words, the more radiation time is increased, the more the stem height and diameter will decrease. The highest height (177.66) was obtained from one-day radiation and the increase in radiation time up to 3 days resulted in 38% decrease in plant height. The thickest stem size (2.56) was also obtained from one-day radiation, along with a 48% increase by a 3-day radiation.
Root length and weight was also influenced by Gamma radiation. One-day radiation increased the root length more than that of the control treatment, whereas the increase for longer than one-day radiation resulted in significant reduction of root length and weight (Table 2). The longest root obtained from one-day radiation and the root weight (104.33) was that of the control treatment. Three-day radiation treatment resulted in 20% and 76% reduction of root length and weight compared to those of the control treatment respectively.
Weight of plant, fruit, and seed were also influenced by Gamma radiation. The heaviest plant, fruit, and seed (1154.33gr, 315.66gr and 758.97gr respectively) were obtained from one-day radiation treatment. The increase in radiation time resulted in significant reduction in fruit, plant, and seed weight. The plant, fruit, and seed weight showed 76%, 50%, and 51% reduction respectively in three-day radiation compared to those of one-day radiation.
The number of ears and leaf width were also influenced by Gamma radiation. The number of ears (2.36) in one-day radiation treatment was the largest among of all treatments with a significant increase. Leaf width (10.46) also showed significant increase compared to that of other treatments in one-day radiation.
Considering the obtained results, scientific use of nuclear methods to increase the agricultural products and their quality in morphological fields was proved to be obviously effective. Therefore, an appropriate dose should be specified in order to succeed in a modification program through mutation. The effect of radiation on height increase in other plants such as Sesame (Sesamum indicum) is previously reported .According to the studies conducted by Gustafsson et al., 1966, internode lengthening during radiation or intracellular hormonal imbalance result in plant lengthening .
Other studies have also reported internode lengthening in Arugula (Eruca sativa) by Gamma radiation, which is caused by the increase in Gibberellin hormone . Gamma radiation significantly increases the length and width of leaves in Barley (Hordeum vulgare), which is in line with our results in the present research . Stimulation of cell division by radiation is reported as the reason for leaves widening and lengthening . Stem thickening through radiation has been observed in corn plant . There is a hypothesis about the effect of lower intensity of Gamma radiation, which is stimulating, and then the changing hormones or results in an increase in antioxidant capacity of cells. Hence, such daily stress factors as fluctuations in light intensity and temperature during growth conditions can be easily overcome in order to achieve better growth . In addition, the radiation of the seed results in stem thickening and strengthening .
The increase in the number of wheat ears due to Gamma radiation has previously been reported  while this increase occurs in lower doses due to the change in plant cells as well as the increase in growth hormone Kinetin (a type of Cytokinin) . As a result, the increase in Cytokinin, being comparatively more than Auxin, leads to germination and therefore increases the flowering . However, higher intensities can cause biological damages and a resultant increase in mutation.
According to Abdul et al., (2010)  and Veeresh et al., (1995) , Gamma radiation increases dry/fresh weights in lower intensities and then decreases them in higher intensities. Such decrease can be interpreted as decrease in stem contents during the stress caused by radiation and the change in plant’s metabolic system in addition to a relative increase in proteins synthesis rather than the membrane in fresh and dry weights respectively.
Generally, considering the results, it is concluded that there should be sufficient knowledge about the effect of Gamma radiation on the desired product and about the optimal intensity in order to improve the crop yield in which the lower intensities of Gamma radiation have resulted in optimum effect in most studies.
Totally, the results of the present study showed that application of nuclear technology and Gamma radiation was effective on morphological and phytochemical properties of corn; in other words, applying this modern scientific method can be useful in improvement of corn growth factors. In addition, using Gamma radiation technology increased the general yield of this plant.
Study of the phenotypic properties
The present research aimed to study the external genetic variations resulted by radiated corn seed. Figure 1 shows the changes in the height of a perfect plant (i.e. root and external organs). The results showed that the plant height of sample #2, the seed of which having been radiated by Gamma for 24 hours before planting, was higher than other samples. Sample #4, the seed of which having been radiated for 72 hours, was the shortest plant. Although the number of ears and seeds in addition to seed weight was reduced in sample #4, the plant shortening can be interpreted as a positive change resulting in less water consumption and is therefore an appropriate choice against drought and water shortage especially in different areas facing such problems.
Figure 2 shows changes in root length and size in which sample #2 and #4 have the biggest and smallest size respectively.
Fig 1 – changes in perfect plant (root and external organs) height of the corns the seeds of which radiated before planting (1: control 2: 1-day radiated 3: 2-day radiated 4: 3-day radiated).
Fig 2 – changes in root length and size of the corns the seeds of which radiated before planting (1: control 2: 1-day radiated 3: 2-day radiated 4: 3-day radiated)
Fig 3 – the control corn sample
Figure 4 shows the corn sample the seeds of which having been radiated for 24 hours before planting. According to Tables 1 and 2, this sample had the most value of morphological properties in comparison with other samples. The remarkable point in Figure 4 was the seeds order, which is an important factor: a genetic mutation resulted in such an order and can be regarded as a positive mutation and the genetic science can extract and transfer this gene.
Fig 4 – a corn sample the seeds of which radiated for 24 hours before planting
Figure 5 shows a corn sample the seeds of which having been radiated for 48 hours before planting. According to Tables 1 and 2, a significant drop was observed almost in all morphological properties of this sample compared to those of the control sample; nevertheless, as seen in Figure 5, the seeds were germinated inside the ear before harvest, showing that this sample was ripen earlier than other samples and the mutation in the gene of this sample had resulted in earlier ripening.
Fig 5 – a corn sample the seeds of which radiated for 48 hours before planting
Figure 6 shows a corn sample the seeds of which having been radiated most among other samples before planting, showing the least value of morphological properties. For instance, the shortening of the plant height in this sample can be regarded as a positive change against drought and water shortage due to the resultant decrease in its consumption of water.
Fig 6 – a corn sample the seeds of which radiated for 72 hours before planting
Considering the obtained results, scientific application of nuclear methods with the aim to increase the agricultural products and their quality is remarkably effective on morphological and phytochemical aspects. In this regard, appropriate doses ought to be specified in order to succeed in modification programs through mutation. There is a hypothesis about the effect of lower intensity of Gamma radiation, which is stimulating and then changing the hormones or resulting in an increase in antioxidant capacity of cells. Therefore, such daily stress factors as fluctuations in light intensity and temperature during growth conditions can easily be overcome in order to achieve better growth. Gamma radiation with lower doses was studied on several plants, resulting in the increase and improvement of most morphological and phytochemical properties due to changes made in plant cells in addition to the increase in growth hormone Kinetin. The results of the present research about corn seed also confirmed the positive effects of radiation with low doses, while higher doses could cause biological damages and the resultant increase in mutation.
Gamma radiation increases dry/fresh weights in lower intensities and then decreases them in higher intensities. Such a decrease can be interpreted as the decrease in stem contents during the stress caused by radiation, as well as the change in plant’s metabolic system in addition to a relative increase in proteins synthesis rather than the membrane in fresh and dry weights respectively. According to the previous studies, it is possible that Gamma radiation can cause disruption in hormonal balance, gas amount, water amount, and the activity of leaf enzyme which leads to changes in plant cellular structure, metabolism, photosynthesis, and the accumulation of phenolic compounds. In this regard, chloroplasts are more sensitive against Gamma radiation than other cellular organelles and the increase in pigment is obvious in radiated samples.
Therefore, there should be sufficient knowledge about the effect of Gamma radiation on the desired product and about the optimal intensity in order to improve the crop yield in which the lower intensities of Gamma radiation result in optimum effect in most studies. Physical mutation through Gamma radiation is one possible way to achieve diversity; mutation is useful equipment for artificial mutation besides making sustainable changes in plants directly and shortening the plants modification way. According to the obtained results, it was concluded that planting several generations on the obtained treatments in addition to conducting more studies about different doses is needed in order to obtain the best dose with the best effect. Generally, the results of the present research showed that using nuclear technology (Gamma radiation) was effective on morphological and phytochemical properties of corn plant and applying this modern scientific method can be useful in improvement of growth factors, the secondary metabolite type, and the rate of this precious plant.
Genetic science is always helpful in human progress through extraction and transfer of genes in different human, animal, and plant species. Corn, as one of the basic nutrients of humans was studied in this research and the obtained results are presented in Charts 1 and 2 in addition to Figures 1 to 6. The present research, with the help of genetic science, produced a new transgenic corn plant, proving that it is possible to have a corn with seeds more in numbers and weight, more well-ordered, earlier harvest-time, and stronger against drought and water shortage, all through transferring the strengthened properties by radiation.
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Cite this Article: Mirhabibi M, Mirzaei MAV, Askari MB and Tikdari M (2016). Studying the effect of Gamma Ray on Morphological and Phenotypic Properties of Corn. Greener Journal of Agricultural Sciences, 3(1): 001-008, http://doi.org/10.15580/GJPNS.2017.1.122116217