关键词: 水稻秸秆, 高温浸提, 酶解, 液质联用, 促生

Abstract:

【Objective】 To explore the effect of agricultural wastes (rice straw) on plant growth, the identification and analyzation of the small molecules that may exist in the high-temperature extracts and enzymolysis solution of rice straw were performed, and the promoting effect of these substances on cucumber growth was also evaluated.【Method】 The high-temperature extract solution of rice straw was prepared by high temperature water extraction at 115℃ for 30 min. The condensation of the extracellular proteins from Trichoderma guizhouense NJAU 4742 under the induction of rice straw was obtained by ammonium sulfate precipitation method, which was used to hydrolyze the rice straw to prepare rice straw enzymatic hydrolysate. The high-temperature extract and enzymolysis solution of rice straw were diluted into different times, and the growth-promoting effects were verified by cucumber hydroponic experiment. The high-temperature extract and enzymatic hydrolysis of rice straw were identified and compared by UHPLC-QE-MS non-target metabolomics detection technology. Under the control of the acquisition software (Xcalibur 4.0.27, Thermo), the QE mass spectrometer collects primary and secondary mass spectrometry data in the information-related acquisition mode for the high-temperature extract and enzymatic hydrolysate of rice straw. Through the self-written R program package (the kernel was XCMS), the original data was processed for peak identification, peak extraction, peak alignment and integration, and then it was matched with the BiotreeDB (V2.1) self-built MS database for substance annotation. Finally, the growth-promoting effects of some identified substances were verified by the cucumber hydroponic experiment.【Result】 The results showed that both high-temperature extract and enzymatic hydrolysate liquid of rice straw could promote the growth of cucumber seedlings at appropriate concentrations, and the enzymatic hydrolysate of rice straw showed significant growth promoting effect on cucumber when diluted for 100 times. Compared with the CK, the dry weight of overground part, underground part and plant height of cucumber plants treated with 100 times dilution increased by 52.64%, 55.05% and 21.43%, respectively, and the number of plant root tips increased by 31.95%. The high-temperature extract of rice straw owned the best growth promotion effect when it was diluted 50 times, in which the dry weight of overground part, the underground part and the plant height of cucumber plants increased by 44.16%, 63.38% and 55.56%, respectively, and the number of plant root tips increased by 64.44%, compared with CK. The UHPLC-QE-MS non-target detection technology results showed that 714 different substances were identified in the high-temperature extract of rice straw and 638 different substances were identified in the enzymatic hydrolysis solution, among which acetylcholine, L-carnitine and myo-inositol were screened out. Meanwhile, the standard products of these three substances were added to the cucumber root system, and the results showed that they all had considerable promotion effect on cucumber growth. Acetylcholine at the concentration of 1 μmol·L^-1, 10 μmol·L^-1 and 100 μmol·L^-1 could all promote the growth of cucumber. Compared with CK, the exogenous acetylcholine at 1 μmol·L^-1 concentration increases the dry weight of cucumber shoots by 54.69% and the dry weight of roots by 73.67%, the number of root tips increased by 130.5%; Exogenous L-carnitine was beneficial to the growth of cucumber plants at the concentration of 0.1 mmol·L^-1 and 1 mmol·L^-1. Compared with CK, the dry weight of cucumber shoots increased by 33.79% and 30.19%, and the dry weight of roots increased by 44.97% and 48.82%, the number of cucumber root tips increased by 41.8% and 49.9%, respectively; Exogenous myo-inositol at the concentration of 0.05 mmol·L^-1 and 0.1 mmol·L^-1 could promote the growth of cucumber. Compared with CK, the dry weight of cucumber shoots increased by 36.66% and 30.15%, roots dry weight increased by 69.82% and 51.78%, and the number of cucumber root tips increased by 149.0% and 96.7%, respectively.【Conclusion】 In brief, both the high-temperature extract and the enzymatic hydrolysate of rice straw could significantly promote the growth of cucumber, and the acetylcholine, L-carnitine and myo-inositol were detected by LCMS in the pyrolysis and enzymatic hydrolysate of rice straw, which were considered as the functional substances in rice straw.

Key words: rice straw, high-temperature extraction, enzymatic hydrolysis, LCMS, growth promotion