عنوان مقاله [English]
نویسندگان [English]چکیده [English]
Background and objectives: Rapid, uniform and complete germination of seeds causes optimum seedling emergence and early growth. Early optimum growth results in more solar radiation interception and increases yield. The germination of purple coneflower is low and non-uniform. One of the reasons of low germination is low permeability of internal membranes. Seed priming is very simple procedures which can improve germination and seedling establishment. One of the biophysical ways of seed priming is pretreatment of seeds with ultrasound. Continuing wave-resulted beating increases the permeability and enhances water absorption and temperature. The increased imbibition rate accompanies with speedy changes in seed metabolism. Imbibition triggers hydrolytic enzymes activity for synthesis of main sugars, amino acids and fatty acids. These compounds are transferred to embryo axis and used for production of new materials. This experiment was aimed at studying the ultrasonic wave’s effect on germination, activity of alpha amylase, sugars, chlorophyll, hydrogen peroxide, and some antioxidant enzymes in germination and seedling stages of purple coneflower.
Materials and methods: In 2016-2017, an experiment was conducted as completely randomized design with 5 treatments and 4 replications in Agriculture Faculty of Shahrood University of Technology. Treatments were irradiation durations of 0, 10, 15, 20 and 25 minutes by ultrasonication device. The measured traits were maximum germination, germination rate, seed reserve use efficiency, seedling dry weight, alpha amylase, total sugar, reducing sugars, non-reducing sugars, ratio of non-reducing to reducing sugars, electrical conductivity, hydrogen peroxide, catalase, guaiacol peroxidase, polyphenol oxidase, glutathione -S transferase, and chlorophyll a and b.
Results: The analysis of variance results showed that pretreatment of seeds with ultrasonic waves affected significantly all studied traits. The highest amount of germination percent and seedling dry weight was obtained from seeds irradiated for 15 minutes. The maximum germination rate and seed reserve utilization was for irradiation durations of 15 and 25 minutes. All irradiation levels increased the activity of alpha amylase, total sugar, non-reducing sugars compared to control. The highest amount of non-reducing sugars was found for 25. Irradiation enhanced electrical conductivity and hydrogen peroxide in comparison with control. For most cases, all irradiation durations increased antioxidant enzymes and consequently enhanced amount of chlorophyll a and b in comparison with control.
Conclusion: The irradiation increased seed vigor. The best irradiation duration, by which both germination and seed biochemical properties were increased, was 15 minutes. Naturally, with increasing germination rate and germination percent in farms, the utilization of growth resources like water and nutrients gets improved. Generally, ultrasonic waves with promoting activity of germination enzymes, biochemical properties and germination indices can be used as stimulator of germination, accelerator of germination of low-germinating seeds.