| Microalgae is an important component of soil microorganisms,rich in resources,and has the characteristics of nitrogen fixation,carbon fixation and secretion of plant growth hormones.It has good effects in promoting crop growth,improving soil fertility and soil structure.In this study,one green microalgae strain was isolated and purified from the soil of vegetable greenhouses in the Hexi region.Three strains of bacteria associated with microalgae were also isolated and screened.The microalgae and bacteria were mixed to prepare microalgae liquid fertilizer,and wheat was used as the experimental material.The fertilizer effect was verified by soaking seeds and pot experiments.The research results obtained are as follows:(1)A green microalgae strain was isolated and purified from the soil of the vegetable greenhouse in Hexi area,named ZW.Observation by light microscope revealed that the microalgae cells were round or oval,with equilateral double flagella.Further identification by molecular biology,the sequence of the microalgae ZW and Chlamydomonas debaryana are identical,and the similarity is 100%.Therefore,it is determined that the microalgae ZW is a Chlamydomonas,Chlamydomonas debaryana.The growth conditions of microalgae ZW were studied,including three factors: culture temperature,initial culture pH and light intensity.The results showed that ZW was most suitable for growth under the conditions of temperature 20°C,initial pH 6.5 and light intensity 8000 lx.(2)Three bacteria were isolated and screened from the original microalgae solution.,named as W1 H1 and G1,respectively.The three strains were identified as belonging to Pseudomonas sp.(W1),Flavobacterium album(H1)and Aeromonas sp.(G1),respectively.The nitrogen-fixing and phosphorus-dissolving properties of three strains of bacteria were measured.It was found that strains W1 and G1 had nitrogen-fixing ability,and the total nitrogen content in the bacterial solution was 6.42 mg/L and 4.27 mg/L,respectively.The strain W1 had better phosphorus-resolving ability,and the amount of phosphorus-resolving was 23.07 μg/m L.Therefore,strains W1 and G1 were selected as fermentation strains,and the composite bacterial solution in which strains W1 and G1 were mixed with a volume ratio of 1: 1 was used in subsequent experiments.(3)The compound bacteria and microalgae ZW were selected for mixed fermentation and the conditions were optimized.Firstly,the fermentation medium was optimized,it was found that the highest biomass obtained with the simplified TAP and LB media were mixed as a fermentation medium.Secondly,through single-factor experiments,the optimal algal-bacterial mixture ratio,culture temperature,and light intensity were determined.The results showed that the algal-bacterial ratio(v/v)at 10:1,temperature at 30°C,and light intensity at 12000 lx were the optimal fermentation conditions to the accumulation of extracellular polysaccharides and biomass of bacterial and microalgae.Therefore,the optimal fermentation conditions for algae and bacteria were determined.(4)The effect of fertilizer was verified through soaking experiments and pot experiments.The results showed that the treatment method with soak the seeds in pure water,and then add the liquid microalgal-bacteria fertilizer can increase the germination potential and germination rate of wheat seeds,with the increase rates of 50.94% and 16.25%;When the microalgalbacteria fertilizer is applied,the dilution factor can affect the growth of the crop.Among them,the 50-fold dilution has the most significant effect on promoting the stem and root length,fresh weight and dry weight of wheat.In addition,compared with other types of algal fertilizer,the microalgal-bacteria fertilizer are more effective than single microalgae or a mixture of multiple microalgae. |
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