Effect Of N、P Conditions On Growth And Nutrition Quality Of Duckweed

Duckweed plants with fast growth, high removal rate of N、P, adaptability, strong resistance, widely distributed, easy to harvest, etc. Duckweed plants has been widely used in abroad contaminated river restoration.Duckweed has been extensively studied, and a great amount of work were concentrated in the duckweed on wastewater treatment, the effects of different factors on the growth of duckweed, etc. But there were few work on the influence of growth factors on duckweed nutrient quality. With the further understanding of the nutritional value of duckweed, the research of duckweed would be further, more detailed, such as strict control growth conditions, to find the growth, quality changes of duckweed, removing harmful substance of the sewage after treatment duckweed, duckweed plant substances extraction etc.The results were as following:(1)With Spirodela polyrrhiza, Spirodela oligorrhiza, Lemma minor as material, three gradient concentration of N:0.05,0.5,1.0mmol/L, and NH4+-N and NO3--N content ratio of5/0,4/1,3/2,2/3,1/4,0/5were set for training test, observation items included growth changes, nutritional quality of duckweed and total nitrogen, total phosphorus removal from cultivation solution.(2) With Spirodela polyrrhiza, Spirodela oligorrhiza, Lemma minor as material, three gradient concentration of N:0.05,0.5,1.0mmol/L was set with NH4NO3, phosphorus concentrations of0.01,0.1,0.3,0.5,0.7mmol/L was treated in the training test, changes of growth, nutritional quality of duckweed and changes of total nitrogen, total phosphorus removal were observerded.The results are as following:(1) In the suitable environment, ability of biomass accumulation for the duckweed was Lemma minor> Spirodela oligorrhiza> Spirodela polyrrhiza. In low nitrogen supplication condition, nitrogen concentration was the main factor influencing the growth of duckweed. Highest biomass of Spirodela polyrrhiza was obtained in the medium of0.05mmol/L nitrogen and O.lmmol/L posphorus, In middle and high nitrogen concentration, ammonia nitrate ratio at1/4,0/5, concentration of phosphorus0.1～0.3mmol/L was more suitable for the growth of Spirodela oligorrhiza and Lemna minor. (2) Improving nitrogen concentration of the culture solution could effectively improve the content of nitrate in the three kinds of duckweed. Under the condition of low nitrogen supplication, phosphorus was not the main factors influencing the nitrate content of Spirodela oligorrhiza and Lemma minor. Under the condition of high N, increasing P concentration could obviously reduce the nitrate content of Lemna minor and Spirodela oligorrhiza, improve the quality of the two kinds of duckweed. Improve the ratio of nitrate nitrogen of the solution, nitrate content of pirodela oligorrhiza had been significantly influenced.(3) In low nitrogen supplication condition, nitrogen concentration was the main factor affecting soluble protein content of the three duckweed. Protein content of three kinds of duckweed treated with middle and high nitrogen concentration was relatively higher than that with low nitrogen concentration. In middle and high nitrogen concentration, higher group of soluble protein of the three kinds of duckweed could be obtained with the ammonia nitrate ratio of1/4,0/5..(4) In middle nitrogen concentration, ammonia nitrate ratio of1/4,0/5were more suitable for soluble sμgar accumulation of the three duckweed. phosphorus concentration was not the main factor affecting soluble sμgar content of three duckweed.(5)The Vc content of three duckweed from high to low were as Spirodela oligorrhiza, Lemna minor, Spirodela polyrrhiza. Change of Vc contentis of three duckweed was not consistent biomass. Condition of middle and high nitrogen, phosphorus concentration of0.01,0.1mmol/L could promote the Vc synthesis of Spirodela polyrrhiza and Spirodela oligorrhiza, low nitrogen concentration, phosphorus concentration of0.1,0.3mmol/L could promote the synthesis and accumulation of Lemna minor Vc.(6) Too low nitrogen, phosphorus concentration was not conducive to the absorption of nitrogen, phosphorus of duckweed. To the elimination rate, to improve the nitrogen, phosphorus concentration could not effectively improve the ultimately eliminate rate of nitrogen and phosphorus. For the total perspective, increase the concentration of nitrogen, phosphorus could greatly improve the ultimately eliminate amount of the three duckweed.