Impact of gamma rays on the germination
To find out LD50 dose for the seed and urther investigate the influence on germination and seedling parameters.The experimental results revealed that the percentage of germination had decreased after irradiation and the effect become stronger with increase of gamma dose.Parameters such as germination percentage, speed ot germination, mean daily germination, peak value and germination value had significantly decreased with increased irradiation doses.
Similarly seedling parameters viz. , Root length, Shoot length, Vigour index and Root/Shoot length ratio expressed higher reduction at higher doses as compared to non irradiated control.
The study clearly indicated ncrease in the deleterious effects of gamma irradiation at regular intervals, with attainment of LD50 at a dose of 1. 50 kGy. Keywords: Gamma irradiation, Groundnut, Seed germination, Groundnut (Arachis hypogaea L. ) is popularly known as peanut. It is one of the world ‘s most popular oil seed crops, cultivated in more than 100 countries of six continents. It is the single largest source of edible oils in India and constitutes roughly about 50 percent of the total oilseeds production.
Among the major Groundnut growing states there has been consistent increase in area under cultivation in Andhra Pradesh. The groundnut seed mainly comprised of protein, fat, carbohydrate which make it sensitive to radiation induced stress. Among the environmental stresses, the radiation is the most important factor, which limits production of groundnut. This would result in drastic reduction in crop yield and magnitude of reduction would depend on groundnut varieties. Not only the yield of Groundnut but also the quality of products decreases under radiation stress.
The seed stage is a convenient phase in the plant’s life cycle for use in radiological studies to determine relative radio sensitivity of species and the effects of various actors on radio sensitivity. Earlier experiments in this field have indicated that ionizing radiation could cause permanent genetical effects, lethal or beneficial mutations, morphological modifications and other effects in plants. Several factors may be involved in the inhibition of germination and the growth of the plants from seeds following their exposure to high irradiation doses.
A number of radiobiological parameters are commonly used in early assessment of effectiveness of radiation. Methods based on physiological changes such as inhibition of seed germination and hoot and root elongation have been reported for detection of irradiated legumes. Therefore, in present study the response of groundnut seed (cv. Narayan’) to gamma radiation stress on germination and seedling parameters of groundnut was investigated compared to non irradiated seed. ASIAN J. EXP. BIOL. SCI. VOL 4 (1) 2013 61 Impact of Gama Rays on the Seed Germination and Seedling Parameters of Groundnut (Arachis Hypogaea L. …………… M. Aparna et al. MATERIALS AND METHODS The material for the present study comprised of seed of groundnut variety Narayan’. 100 seeds were taken in 0. 1 mm thick polythene bags of 1 5 X 22cm dimension and ealed. The bags were exposed to gamma irradiation wit n doses ot O 1. 30, 1. 50, 1. 70, 1. 90, 2. 10 and 2. 30 kGy. Samples were irradiated in continuous gamma sterilization plant (GC 5000, designed by Board of Radiation and Isotope Technology, Mumbai) with 444 TBq (12000Ci) and Cobalt60 source with a specific activity of 3. 01 kGy/hour at Quality Control Laboratory, Acharya N.
G. Ranga Agricultural University, Rajendranagar, Hyderabad- 500 030 and were compared with the observations made on untreated control. The material for irradiation was placed in an irradiation chamber located in vertical drawer inside the Lead flask. Radiation field was provided by a set of stationary Cobalt60 source placed in a cylindrical cage. The source was doubly encapsulated in corrosion resistant stainless steel pencils and was tested in accordance with international standards. Two access holes of 8 mm diameter were provided of service sleeves for gasses, thermocouple etc. Mechanism for rotating/stirring samples during irradiation is also incorporated. The quantity of absorbed dose (kGy) can be defined as the amount of energy absorbed per unit mass of the matter at the point of interest. The experiment was carried out as per Completely Randomized Design CRD). The irradiated seed along with nonirradiated control were sown in petridishes in the laboratory. Data on germination and seedling parameters were recorded seven days after sowing under ambient condition. Germination percentage was calculated using the formula as per ISTA .
Speed of germination of the given sample was calculated according to the formula given by Maguire . Similarly, other germination parameters viz. , Mean daily germination, Peak value (Edwards ) and Germination value (Czebator ) were calculated. Seedling parameters like Shoot and root length were measured using ten seedlings ollected at random from each sample on 7th day from the seeds subjected to germination test. The shoot and root length were measured in centimeters (cm) using a scale and root/shoot length ratio was calculated using the estimates of seedling length.