| The residue after evaporation（RAE）and the concentrated bacterial solution after ultrafiltration（CBS）are liquid wastes produced in the process of industrial production of vitamin C（Vc）.The main component of RAE is 2-keto-l-gulonic acid（2KGA）,a low molecular weight six-carbon organic acid be used as a source of soil carbon,CBS is rich in bacillus megaterium（CGMCC NO.26402）,which can promote the release of available phosphorus from soil.In this study,Gossypium hirsutum L.was used as experimental material.The seeds were coated by CBS and diluted by 50-fold RAE,to investigate the regulation of Vc industrial waste on the physiological and biochemical processes during seed germination,root and seedling development of cotton in saline-alkali soil,in order to clarify the physiological and biochemical response mechanism of RAE and CBS to promote cotton growth under saline-alkali stress.To evaluate the effects of industrial waste from Vc fermentation on cotton seed germination,seedling stress resistance and rhizosphere microbial community formation,and its potential for agricultural utilization.The results showed that cotton seed germination percentage,root elongation and fresh weight were significantly enhanced by coating seeds with CBS,applying 50-fold dilution of RAE or the combination of RAE and CBS,and the combination treatment had the best result.On one hand,the content of organic matter in alkaline soil of Xinjiang was increased and the p H was reduced to 6.5 in the germination stage of cotton by the combination of RAE and CBS treatments,which provided a more favorable soil environment for seed germination,the seed germination percentage,vigor index and germination index were increased by 37.5%,54.55%and 44.14%respectively.On the other hand,the content of L-ascorbic acid（ASA）in young root increased by 87.73%by increasing the expression level of L-guloronic acid-1,4-lactone oxidase（GLO）gene which catalyzes the transformation of L-guloronic acid-1,4-lactone into ASA.It enhanced abiotic stress resistance during germination and promoted root growth,with root length and fresh weight increased by 19.33%and49.64%,respectively.The expression of Endochitinase（ECA）and Xyloglucan endotransglycosidase/hydrolase（XTH）related to cell wall formation in cotton roots was significantly upregulated,it also showed that the young root cells were more active in division and proliferation.When CBS was coated with seeds and RAE was dilute 50 times,the photosynthetic pigments in the leaves of cotton seedlings were increased to ensure the energy required for normal plant development and enhance the transformation and synthesis of osmotic regulatory substances,the contents of soluble carbohydrate,soluble protein and proline were increased by 58.49%,22.04%and 173.42%respectively,and the osmotic pressure was balanced.The increase of the activities of superoxide dismutase（SOD）,peroxidase（POD）,catalase（CAT）and ascorbate peroxidase（APX）promoted the removal of H2O2 and malondialdehyde in plants,which decreased by 59.37%and 19.13%,respectively.Compared with CK Group,the content of ASA increased by 72.8%and 28.4%respectively in RAE Group and RC Group,this was related to the increased expression levels of key enzyme genes in ASA synthesis and cycling pathway,such as GDP-mannose-3’,5-epimerase（GME）,L-galactono-1,4-lactone dehydrogenase（GLDH）,gulono-1,4-lactone oxidase（GLO）,monodehydroa reductase（MDHAR）and dehydroascorbate reductase（DHAR）.In addition,the expression levels of polyamine oxidase（POA11）and CBF transcription factor gene（CBF3）in RAE group increased significantly,which improved the salt tolerance of cotton.The expression level of Cellulose synthase 8 gene（Ces A8）in RC Group was significantly upregulated,which promoted the growth and development of cotton seedlings.We found that the application of RAE could increase soil organic matter content and microbial abundance in saline-alkali soil,and CBS treatment could increase soil available phosphorus content.Analysis of soil microbial composition after applying RAE,the microbial community that can rapidly utilize the organic carbon in Rae can rapidly multiply and occupy a favorable niche,and the survival and development of other microbial communities are limited,results in the decrease of total OTU count.The increase of soil organic carbon and the regulation of p H are the critical factors that affect the microbial community structure of cotton rhizosphere in Xinjiang saline-alkali soil.In this study,the response of cotton seed germination and the growth and development of seedling in the saline-alkali soil to coating cotton seeds with CBS and applying RAE was studied,the effects of 2KGA-enriched RAE on ASA pathway in cotton seedlings were studied,which provided a theoretical basis for the resource utilization of two kinds of Vc industrial wastes and developing a new planting technology for cotton in saline soil. |
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