The Effects Of Endophytic Fungi Trichoderma Asperellum Cadmium Accumulation Of Maize Seedlings

Cadmium is known as one of the most toxic trace elements in soil and water.It is non-biodegradable and tends to accumulate in living organisms,causing significant threats to both the environment and public health.The cadmium pollution in soil is extremely serious.There are three most commonly methods of remediation to heavy metal pollution:physical remediation,chemical remediation and phytoremediation.Among these methods toremediate heavy metal contaminated soils,the plant-microorganism combined remediation is being considered as an esthetic,cost-effective and eco-friendly technology for broad prospects.It has known that endophytic fungi are potential bio-adsorbents and play important roles in host plant growth and heavy metal tolerance.Trichoderma asperellum as the most tolerant of cadmium was isolated from eight endophytic fungi of Kosteletzkya pentacarpos,Then pot experiment was conducted to understand the effectivition of Trichoderma asperellum increasing cadmium accumulation and cadmium resistance of maize seedlings.1.In this experiment,heavy metal cadmium resistance of eight endophytic fungi from kostelezkya virginica:Trichoderma asperellum,Penicillium funiculosum,Cladosporium sp.,Aspergillus niger.Trichoderma viride,Alternaria tenuissima,Ceriporia lacerata,Penicillium aurantiogriseum.Trichoderma asperellum was the most tolerant to cadmium,followed Ceriporia lacerate,aurantiogriseum,Cladosporium sp.Alternaria tenuissima.Trichoderma viride,Aspergillus niger,Penicillium funiculosum were the most intolerant to cadmium.2.In this experiment,the Trichoderma asperellum was transformed by genetic transformation,and the pCAM-gfp Plasmid profile was transferred to Trichoderma asperellum.Confocal laser scanning microscopy（CLSM）to examine conidial germination and hyphal colonization in the roots of maize seedlings for 72 hours post inoculation.Confocal laser（CLSM）found that Trichoderma asperellum colonizes the root of maize and colonizes intercellularly.3.The stem length,dry weight,fresh weight,chlorophyll contention and root length of maize were obviously increased after colonizating,without cadmium stress the stem length,dry weight,fresh weight,chlorophyll contention and root length were increased 31.60%、142.08%、64.09%、32.78%and 73.02%.The effect of Trichoderma asperellum on maize was not obviously with low cadmium stress（100mg/kg）,but SOD、POD、CAT were increased obviously in leaves,only POD was increased obviously in roots.SOD was increased 40.56%,POD was increased44.50%,CAT was increased 45.10%in leaves.,in roots POD was increased40.01%.With high cadmium（200mg/kg）stress the stem length,dry weight,fresh weight,chlorophyll contention and root length were increased 34.26%、218.06%、105.02%、78.79%and 44.79%,SOD was increased 56.6 0%and 50.40%,POD was increased 37.8%and 70.20%,CAT was increased 44.8%and 55.30%in leaves and roots after colonizating.4.Trichoderma asperellum increased the cadmium bioaccumulation of maize seedlings and increased the cadmium translocation from aerial parts to root zone under cadmium stress.Under low cadmium（100mg/kg）stress,the inoculation of maize seedlings was 2.51 times that of uninoculated total cadmium.Under high cadmium（200 mg/kg）stress,the inoculation of maize seedlings was 1.67 times that of uninoculated total cadmium,compared to uninoculated under low cadmium stress and high cadmium stress,the TF was reduced by 0.12 and 0.11.There was a tendency that the cadmium translocation from aerial parts to root zone.5 Without the cadmium stress inoculated with Trichoderma asperellum,Part of high-affinity NO₃^-transporters genes expression was increased,Under the cadmium stress inoculated with Trichoderma asperellum Part of genes expression of high-affinity NO₃^-transporters and reductases,detoxification and activation of the cellular antioxidant systems were increased compared to uninoculated.These findings demonstrated that the endophytic fungal Trichoderma asperellum symbionts associated with plants play pivotal roles in promoting plant growth,enhancing host tolerance and assisting phytoremediation.