| Trichoderma spp. including T. asperellum, could not only promote plant seeds germination, growth and blooming, but also enhance crop yield. In order to thoroughly study the plant growth promoting mechanism of T. asperellum ACCC30536strain. In this research, tissue-cultured Populus davidiana×P. bolleana seedlings transplanted into fields were induced by T. asperellum conidia solution, and the effects of growth, photosynthesis, concentration of endogenous auxin (IAA) in the leaves, and the expression of PodbARF, PodbAUX/IAA, PodbGH3and PodbSA UR, which involved in auxin signal transduction pathway were analyzed systematically. moreover, the influences of the physical and chemical properties and nutrient component contents of the culturing soil treated with T. Asperellum were also analyzed. The results obtained are as followings:1T. asperellum conidium could have potential significant growth promoting action on tissue-cultured P. davidiana×P. bolleana seedlings transplanted into fields. The increment of heights, stem diameters and roots of poplar seedlings had achieved significant increases treated by different concentrations of T. asperellum conidium. Meanwhile, T. asperellum conidium could not only improve the net photosynthetic rate, intercellular CO2concentration of poplar seedling leaves, but also partly influence the parameters of Pnmax, Rd, LSP, LCP of these transplanting seedlings. In addition, our results showed that the effects on poplar seedling growth, biomass outputs and photosynthesis was significantly related with the concentration of T. asperellum, and the best inducing conidium concentration is5×103cfu per cm3soil.2T. asperellum conidia maybe have potential action of accelerating IAA biosynthesis. The concentration of endogenous IAA in the seedling leaves rapidly increased compared with the control group Con on the first day inducing by T. asperellum conidium at the level of5*103cfu/cm3soil. And the IAA concentration always keeped higher levels compared with the Con group within the following15days.3The qRT-qPCR results showed that the gene expression patterns were significant different compared with the control group induced by T. asperellum. The expressions of gene PodbARF were rapidly up-regulated at the first hour treated by T. asperellum. And the changes of expression abundances of PodbARF were fluctuated greatly. However, the up-regulated expression time of PodbAUX/IAA was falled behind gene PodbARF, and the up-regulated expression of PodbAUX/IAA was always maintained for a long time until48hours, then to down-regulated expression. On the other hand, the gene PodbGH3was expressed up-regulated compared with control group during48hours. Finally, the gene PodbSAUR was expressed quickly up-regulated and down-regulated at short time induced by T. asperellum. The change range of PodbSAUR expression abundance was bigger at the initial stage, and the change range of its expression abundance little by little following the inducing time by T. asperellum. The change range of PodbSAUR expression abundance fluctuated diminution at the time point of48h.4The results showed that it could improve significantly the moisture content, and the contents of organic matter, total phosphorus, available phosphorus, total potassium and available potassium in the soil of the bare soil at different sample collected time points during the experiment stage treating by the level of5*103cfu/cm3soil of T. asperellum conidium (P<0.05). At the same time, as for the soil in the seedling-cultured pots, the heavy T. asperellum conidia treatment improved significantly the soil organic matter, total nitrogen, total phosphorus, available phosphorus and total potassium content at different sample collected time points (P<0.05). Meanwhile, the moisture content of the soil in the seedling-cultured pots was decreased significantly (P<0.05). On the other hand, we also found that T. asperellum might be increased the buffering capacity of the pot-soil thus stabilizing soil pH. |
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