Study Of Moso Bamboo Lignin As A Plant Growth Regulator

Natural cellulose and hemicellulose have been widely used in the production of paper,sugar and fuel ethanol,but lignin,which is second only to cellulose in reserve,has not been well utilized.In this dissertation,bamboo was selected as the raw material to study the effects of sulfuric acid lignin,alkali lignin and lignin treated with hydrothermal alkali activation in regulating plant growth,and the effects of lignin structure changes on plant growth,the regulatory mechanism of lignin on plant growth were studied,and provide reference for the high-value utilization of lignin.Sulfuric acid lignin(SAL)was prepared by Klason method.Bamboo chips were treated with by caustic soda process of 25% available alkali,and alkali lignin(AL)was prepared by treating black liquor with acid extraction.Different concentrations of lignin solution were prepared for the hydroponic experiment of rice seedlings.The results showed that SAL concentration of 0.05% had the best promotion effect on rice seedlings,which increased stem length by 16.0% and root length by 11.9% compared with the control sample.When AL concentration was 0.04%,stem length and root length were increased by 13.6% and 14.8%,respectively.By characterization the structure of lignin,SAL and AL showed no significant difference in the types of active functional groups.The content of hydroxyl and carboxylic groups in SAL lignin was slightly higher than that of AL,but the G/S ratio of SAL in bamboo was significantly lower than that of AL.The effect of SAL on stem length was better,while the effect of AL on root length was better.It was speculated that this phenomenon was related to the structure of lignin and the active groups.Alkali-catalyzing hydrothermal treatment was used to modify bamboo SAL to increase the content of active groups.The effects of hydrothermal degradated bamboo sulfuric acid lignin(Bamboo HSAL)on plant growth regulation were investigated in rice seedling hydroponic experiments.The results showed that the HSAL obtained by hydrothermal treatment at 280℃ had the best promoting effect on rice seedlings.It was further determined that the HSAL of bamboo and Chinese fir had the best promoting effect on rice seedlings when the concentration was 0.05%.Under the above conditions,the stem length and root length of rice seedlings treated with bamboo HSAL were increased by 37.5% and 33.0%,respectively,compared with control sample,but the effect was similar to that of Chinese fir HSAL.Therefore,hydrothermal degradation could significantly improve the promoting effect of bamboo SAL on rice seedlings,but there was no significant difference in the regulatory effect of Chinese fir lignin.Combined with the characterization of lignin structure,it was found that the S/G ratio of HSAL was slightly higher than that of SAL after hydrothermal treatment.In addition,the content of active groups such as hydroxyl and carboxyl in lignin was higher,which showed that it had a better promotion effect on the growth of rice seedlings.The alkali-catalyzing hydrothermal treatment was used to modify bamboo AL to increase the content of active groups.The effects of hydrothermal degradation of bamboo hydrothermal degradated alkali lignin(Bamboo HAL)on plant growth regulation were investigated in the hydroponic experiments of rice seedlings.The results showed that the bamboo HAL obtained by hydrothermal treatment at 280℃ had the best promoting effect on rice seedlings,and further determined that the HAL concentration of 0.04% had the best promoting effect on rice seedlings.Under the above conditions,stem length and root length of rice seedlings treated with HAL increased by25.7% and 44.6%,respectively.HAL had a more significant effect on root length than HSAL.Combined with the characterization of lignin structure,it was found that the content of hydroxyl and carboxyl groups in bamboo HAL was significantly increased by hydrothermal treatment compared with bamboo AL,and was higher than bamboo HSAL,which indicated that the promotion effect of lignin on plants was related to the structure and active groups of lignin.