Ultrasonic Breeding Mechanism

As our country is a large agricultural nation, coupled with the actual situation in China, how to deal with the food problem becomes a long-term thinking topic. The resources of medicinal plants are various and rich in our country. For some medicinal plant seeds, the sprout cycle is long and the germination rate is low, these factors have actual application of medicinal plants to be limited.Along with the development of agricultural production and the acoustic biology, people began to apply sound to plant breeding, which exert remarkable effect, including germination cycle is shorten, germination rate is increased, mildew rate is decreased, yield is improved, etc. Predecessors' research for ultrasound breeding mainly focuses on experimental study and how ultrasound affects some particular plant seeds. According to the theory and practical, this paper discuss on the mechanism of ultrasonic breeding, which can instruct the parameters of breeding sound.This paper establishes the plant seeds cell into single plane round cell membrane, single plane rectangular membrane and single plane elliptic membrane model. Through the way of theoretical calculation and numerical simulation, the resonance frequencies of cell membranes are discussed. Through the experiment and microscope observation, this paper researches the ultrasound time, frequency, sound intensity influence on seed germination rate, sprout potential. The main conclusions:(1) Ultrasound can improve the cell membrane permeability, which is relevant to the electricity effect produced by ultrasonic cavitations. On both sides of membrane, the expression of concentration for the ions is . Concentration gradient makes membrane permeability power to be generated, so permeability is increased.(2) To treat cell membrane as single plane round membrane, theoretical resonance frequency of cell membrane is deduced, which is .a is radius, T is surface tension,σis surface density for membrane. (3) To treat cell membrane as single plane rectangular membrane, theoretical resonance frequency of cell membrane is deduced, which is . a,b are long axis and the short axis for rectangular membrane respectively.(4) To treat cell membrane as single plane elliptic membrane, theoretical resonance frequency of cell membrane is deduced, which is a,b are half long axis and half short axis for elliptic membrane respectively, w is angular is gravity acceleration, a is surface density, S is surface tension. Appling this theory model and calculation formula to seed cells of gynostemma pentaphyllum, found that theoretical value is consistent with experimental value, which confirms the theoretical model has certain correctness.(5) Young's modulus of cell membranes impacts greatly on the vibration resonance frequency of cell membrane, and the larger young's modulus, the higher the fundamental frequency. When the sizes, Poisson ratio, surface density of cell membrane are unchanged, and only change the young's modulus, the vibration modal of fundamental frequency is basically the same.(6) In the case of elliptic membrane, using Matlab to draw the change of frequency with young's modulus, the change is linear. When Young's modulus is less than 400pa, the change of frequency with young's modulus is more significant. For a certain Young's modulus and elliptic membrane, there are various vibration modes. Different vibration modes correspond to different frequencies.(7) The conclusions of experiment:In the case of same ultrasonic irradiation time, the proportion of ultrasonic time and intermittent time impacts on the length of germination cycle. From the experiment, ultrasonic 10s, intermittent 10s is better than ultrasonic 20s, intermittent 20s. In the case of ultrasonic 10s, intermittent 10s, ultrasonic power 20w is best for salvia miltiorrhiza seeds, the followed is100w. Except ultrasonic frequency and ultrasonic time, ultrasonic power has great impact on breeding.(8) When ultrasonic frequency is the same as resonant of cell membrane frequency, it make membranes resonance occur, then energy of sound waves go into cells greatly, which results in a series of biological physical effects.Through the equation to calculate the best frequency of seeds, to design transducer is more targeted. In ultrasonic breeding process, for lack of center frequency and relying on experience blindly experiment, it makes the workload to be increased. This paper calculates the center frequency, which reduces the workload in a certain extent and makes the ultrasonic breeding to be more practical significance.