| The stimulation effect of refined lignin extracted from the pulping waste liquid on plant growth was proved and the refined lignin can be used as a plant growth regulator,and it has been found that its stimulation effect on plant growth is related to the structural characteristics of lignin.In order to provide a high value utilization route for pulping waste liquid,this study selects waste liquid from non-wood fiber alkali pulping mill to explore its effect on plant growth.How will the stimulaotion effect on plant growth change when oxidation modification happened to alkaline pulping waste liquor and the stuctral characteristication of lignin from waste liquor were studied to explor the relationship between stimulation effect and lignin structral characteristic.The results of this research are as follows:1.Effects of pulping waste liquor on seed germination and seedling growth of Chinese cabbage:Chinese cabbage seeds were used as research objects,wheat straw alkaline pretreatment black liquid（ABL）,wheat straw alkali sodium sulfite cooking waste liquor（SSWL）,rice straw oxygen-alkali cooking black liquor（OABL）and Fenton oxidized rice straw oxygen cooking black liquor（FOABL）were diluted to obtain solutions with certain concentrations based on the lignin concentration,wihic were applied to the seed germination and seedling growth experiments of the Chinese cabbage.The results showed that ABL,SSWL,OABL and FOABL could not promote the seed germination of Chinese cabbage seeds,but OABL and FOABL promote the germination rate of seeds,and the germination potential increased by 4%compared with the control.The four cooking wastes liquor solution with a certain lignin concentration range promote the growth of stem length of Chinese cabbage seedlings.The promotion of stem length was most obvious when the lignin concentrations of ABL,SSWL,OABL and FOABL were 50ppm,200ppm,200ppm and50ppm,respectively,the stem length increased by 74%,82%,18%and 26%.respectively.There was no promoting effect on the root length.ABL,SSWL,OABL and FOABL significantly promoted the fresh weight and dry weight accumulation of Chinese cabbage seedling,especially shoot weights.ABL,SSWL,OABL,and FOABL promoted the fresh weight and dry weight of the shoot,and the highest fresh weight of the shoot increased by 65%,46%,48%,and 47%,respectively and he shoot dry weight increased by 59%,10%,55%and 56%respectively.As the root dry weight increased by 35%,18%,64%,54%under the influence of ABL,SSWL,OABL and FOABL respectively and the root length did not increase.The promotion effect on root growth expresses as root hairs and lateral roots increasing.The promotion effect of OABL and FOABL solutions on the growth of Chinese cabbage seedlings was more obvious,than ABL、SSWL solutions.Non-wood alkaline pulping waste liquor showed similar biological activity,expressing promotion effect on growth of plants,as humic acid.2.Oxidation modification of black liquor and effect of oxidized black liquor on the growth of Chinese cabbag plantlets:Fenton oxidation modification was carried out on wheat straw alkali sodium sulfite cooking waste liquor（SSWL）,wheat straw caustic soda cooking black liquor（ABL）and straw oxygen alkali cooking black liquor（OABL）to obtain fenton oxidation modified wheat straw alkali sodium sulfite cooking waste liquor（FSSWL）,fenton oxidation modified wheat straw caustic soda cooking black liquor（FABL）,Fenton oxidation modified straw oxygen alkali cooking black liquor（FOABL）.SSWL and its FSSWL expressed inhibition effect on the growth of Chinese cabbage plants.Under the influence of ABL solution with the lignin concentration of 50ppm and below,the growth of stems and leaves and roots weights were promoted.The highest fresh weight of stems and leaves and the fresh weight of roots increased by 27%and 42%,respectively.OABL,FABL and FOABL only promoted the accumulation of organic matter in the stems and leaves of Chinese cabbag plantlets when the lignin concentration was less than 50ppm,and the highest fresh weight of stems and leaves increased by 8%,9%,and 24%compared with control,respectively.When the concentration of lignin was 25ppm,the oxygen-alkali black liquor promoted the growth of the roots of Chinese cabbage plants,and the fresh weight of roots increased by 12%compared with the control.After Fenton oxidation modification,ABL and OABL did not promote root growth.Inhibition on plant growth was exhibited when the concentration of lignin came higher.The growth of Chinese cabbage plants in different growth stages responded differently to the treatment of pulping waste liquid.The promoting effect on growth Chinese cabbage plants that pulping waste liquid expressed was more significant in the seedling stage than in the growing period.3.Structural characterization of black liquor lignin:extraction and purification of lignin from wheat straw caustic soda cooking black liquor（ABL）and straw oxygen-alkaline cooking black liquor（OABL）were conducted,and infrared spectroscopy,31P nuclear magnetic resonance spectroscopy,1H-13C two-dimensional nuclear magnetic resonance spectroscopy structure characterization were taken on lignin from ABL、OABL.The results showed that both ABL lignin and OABL lignin were GSH-type lignin,and the structure of aromatic ring in OABL lignin changed during chemical reaction during cooking.The singal strength of benzene ring in 2D NMR spectrum was weaker than lignin from ABL.The signal of the bond between lignin units in lignin from OABL is less than that of lignin from ABL,which is consistent with the results of quantitative determination of hydroxyl content and carboxyl content in phosphorus spectrum.The hydroxyl content of lignin from OABL is 0.55mmol/g-lignin more than lignin from ABL,the aliphatic hydroxyl group and the phenolic hydroxyl content are 0.28 and 0.27 mmol/g-lignin higher than that of lignin from ABL,respectively.The carboxyl content is 0.77 mmol/g-lignin higher than that of lignin from ABL.The content of condensed phenolic hydroxyl in lignin from ABL is 0.13mmol/g-lignin slightly higher than that of lignin from OABL.The rupture of lignin unit linkage bond during oxygen-alkali cooking is more intense than that in the caustic soda-cooking process.ABL and OABL lignin also coumaric acid and ferulic acid,and lignin from OABL contain more content of small molecule organic acids than lignin from ABL.When the content of active groups in lignin,such as aliphatic hydroxyl group,phenolic hydroxyl group and carboxyl group,is more,it can promote the growth of Chinese cabbage seedlings and early plant growth.When the contents of the Lignin-derived compounds that inhibits the growth of Chinese cabbage plant such as coumaric acid and ferulic acid increase the pulping waste liquid expresses an inhibitory effect on Chinese cabbage plant growth. |
