| Plants grown in cells of plug tray often show limited growth due to low levels of water holding capacity and fertilizer conservation in the medium. Water and fertilizer supplied steadly is critical to produce srtong seedlings. y-Poly glutamic acid (y-PGA) and phosphorus soluble bateria M20 was used to enhance the fertilizer availability and induce the rhizosphere microecologe. In this study, tomato and watermalon was used as experiment material. Firstly, The optimal concentration of y-poly glutamic acid application was chosed from five treatments which was mixed with the substrates before sowing. Physicochemical properties of substrates and growth parameters of plug seedlings were measured. And then four different treatments were established: CK, M20, y-PGA and M20+?-PGA. The growth and development parameters and nigtrogen and phosphorus absorbtion of plug seedling were measured. Colonization by GFP-marked M20 on root surface of watermalon root hair zone and rhizosphere were observed by fluorescence microscopy. Illumina MiSeq sequencing was used to characterize the rhizosphere bacterial communities of tomato and watermalon seedling. The main results showed as follows:At the beginning of the treatment, y-PGA improved the water filled porosity, water holding capacity, EC value, and the contents of NH4+-N, NO3--N, olsen-P, available K, exchangeable Mg and Ca in the substrates, while the pH values were reduced. At the seedling growth stage, y-PGA increased the available N, P, Ca and Mg contents in the substrate, especially improved the enzymatic activities of phosphatase and catalase at the late growth stage. For the tomato seedlings, chlorophyll contents increased with the increasing y-PGA. The highest root activity was obtained in the treatment of 3 kg·m-3 ?-PGA. y-PGA mainly improved the shoot growth but restrained the root growth applied by either mixing with the substrates before sowing or watering with ?-PGA solution. ?-PGA showed a delayed effect on the growth of tomato seedlings, and the effects were much better for the late-stage seedlings than early-stage seedlings.-The leaf area, stem and leaf dry weight, root dry weight, seedling index and phosphorus absorbtion of tomato were enhance by M20 inoculation, y-PGA addition and both applied M20 and y-PGA. The phosphatase activity and phyte activity were increased too. Otherwise the rhizosphere bacterial communities was changed and bacterial diversity was reduced. Some beneficial bacteria genera (e.g. Streptomycetaceae unclassified) were enhanced by M20 inoculation and Some beneficial bacteria genera (e.g. Pseudomonas, Nitrosospira, Cupriavidus and Bacillus) were enhanced by y-PGA addition. y-PGA addition did not affect the colonization of M20.-The water filled porosity,water holding capacity, NH4+-N, NO3--N, olsen-P, available K, exchangeable Mg, exchangeable Ca, microbial activity, neutral phosphatase activity and catalase activity were improved by y-poly glutamic acid and pH was reduced. Effects of y-poly glutamic acid on watermelon seedling were more obvious at the late growth stage than that at the early growth stage. The shoot biomass and leaf area were maximum in the treatment of 3 kg·m-3 y-poly glutamic acid at the late growth stage which were increased by 22.6% and 55.7% respectively compared with that in the control.-The shoot height, stem diameter, leaf area, stem and leaf dry weight, seedling index, substrate phosphatase activity and phosphorus absorbtion of watemalon seedling were enhance by M20 inoculation, y-PGA addition and both applied M20 and y-PGA. Otherwise the rhizosphere bacterial communities was changed and bacterial diversity was reduced. Some beneficial bacteria genera (e.g. Streptomyces) were enhanced by M20 inoculation and Some beneficial bacteria genera (e.g. Pseudomonas, Nitrosospira, Bradyrhizobium, Cupriavidus and Bacillus) were enhanced by y-PGA addition. y-PGA addition did not affect the colonization of M20.In conclusion, either M20 inoculation or y-PGA addition enhanced nutreient available of substrate and substrate phosphatase activity and changed rhizosphere bacterial communities and increased some beneficial bacteria genera and promoted the growth and development of sedlings and strong seedling production. |
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