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In the review of the application of naphthylacetic acid (NAA), the development trend of domestic and international pesticide formulations and nano-suspension particle dispersion techology, this paper combines conventional microemulsion method with ultrasonic dispersion technique to prepare NAA nano-suspension, and comparing with the original agent preliminary studies this agent effect on the Medicago sativa L.(alfalfa) tube-seedling growth, in order to improve the effective utilization of NAA in plant tissue culture, shorten the rooting time and further improve the alfalfa Group Tissue Culture and industrialized breeding system. The main research work are as follows:1. Preparation of NAA nano-suspension: Using microemulsion-phacoemulsification method, the concentration NAA is0.4g·L-1, the amount of dispersant Tween80is about1%, the sample speed is8mL·min-1, the ultrasonic time is60min.2. Characterization of the NAA nano-suspension: Being detected by transmission electron microscopy, the particles disperse well,and the average size is about50×150nm. After infrared spectroscopy, its structure and composition are not basically changed.3. The optimal concentration range of NAA nano-suspension which is suitable for alfalfa plantlets culture is0.2～0.5mg·L-1, in which1/2MS+0.5mg·L-1is the best medium for alfalfa rooting, and plants grow best.4. NAA nano-suspension which is at low concentration(0.2～0.5mg·L-1) has a significant role in promoting the rooting rate, plant height, stem diameter, the above-ground biomass and the under-ground biomass. When the concentration is0.5mg·L-1, promoting effect is best. Compared with the original agent, above-mentioned indictators respectively increase by13.1%,24.8%,6.4%,11.9%,23%and17.3%.5. The effect of NAA nano-suspension on the chlorophyll content and root activity of alfalfa plantlets shows promotion at low concentration, inhibition at high concentration. Compared with the contrast group (CK), the content of chlorophyll and root active absorption area of alfalfa plantlets which are treated with0.5mg·L-1NAA nano-suspension obviously increase by78.3%and35.8%. And compared with the original agent, the indictators respectively increase by23.9%and7.5%.6. Different concentration of NAA nano-suspension has different impacts on MDA content, POD and SOD activity. Compared with CK, the content of MDA in alfalfa tube-seedlings treated with0.5mg-L"1NAA nano-suspension decrease by37.1%, the activities of POD and SOD are highter, increasing by40.9%and32.6%. And compared with the original agent, the content of MDA decrease by23.7%, the activities of POD and SOD increase by15.5%and13.7%, the treatment effect is significant.
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