| As one of the important renewable energy,bio-energy provided a kind of new pathway to solve the major problems such as energy crisis and global warming.Lignocellulose is the main raw material for the production of energy,also is main components of the cell wall.And the herbaceous plants with high fiber content and high yield are considered to be the important lignocellulose.Lignocellulose is mainly composed of cellulose,hemicellulose and lignin,however,lignin is considered to be main physical barriers for reducing the enzyme degradation efficiency of lignocellulose.In view of the problem that there are low industrial conversion efficiency of cellulose and hemicellulose in biological energy production and utilization,as well as the use of bioenergy plants have some controversy,this experiment was carried out.It is selected the annual gramineous crops of maize,perennial alfalfa and annual legume forages chenopodiaceae weeds lambsquarters as the research object,researching the characteristics of development and deposition of lignin in cell walls,and analyzing the values of degradation degree of lignin acquired by the different pretreatment methods for different biomass material,in order to provide theoretical basis for biofuel production of lignocellulose.Results were as follows:1)For the three plants maize,alfalfa,lambsquarters in different development periods slice processing on sectioning,staining and observing autofluorescence,it is found that the structure of alfalfa and lambsquarters stems cross section was relatively similar,and both of them have different the stem structure with the maize.The original lignin deposition sites in all three kinds of plant stem was the primary xylem,then the lignin deposited in the secondary xylem and other lignification stems tissue.Both of S and G lignin were all deposited in the three kinds of plant stem,and the sedimentary area were all the same.The stem lignin deposition area of alfalfa and lambsquarters was the primary xylem and secondary xylem,and discontinuous lignin deposition in the phloem.Both of S and G lignin in phloem were showed discontinuous sedimentation.Maize stem lignin deposited in the primary xylem and secondary xylem and sclerenchyma,but there is no lignin deposited in the phloem.In addition,lambsquarters epidermis green groups also have a small amount of lignin deposition,while alfalfa and maize found no lignin deposition in epidermis.Lignin deposition in stem was all begins in young period of the three plants,and the constantly deposited was accompanied by the growth and development of the plants.There are still a few of lignin deposition when the plants become fully mature.2)The morphological,biomass and lignin contents of the three plants maize,alfalfa,lambsquarters in different development periods were analyzed,the results:plant height,stem diameter and other the morphological indexes of maize and alfalfa maximizing in the flowering period(anthesis to tasseling for maize),and there are no significant changes found in the later growth period.The stem and leaf biomass of this two kinds of plants reached maximum in milk stage(maize)and green pod stage(alfalfa),and the maximum values of the stem and leaf biomass:maize stem 587.23 g/plant,maize leaf 171.51 g/plant,alfalfa stem 401.36 g/plant,alfalfa leaf269.06 g/plant,respectively.And lambsquarters morphological indexs and biomass unceasingly increase along with the growth and development,and reaching the maximum at full maturity period.The maximum values of stem and leaf biomass are 292.53 g/plant,142.14 g/plant,respectively.The maximum biomass of the three plants are 39.45 t DM/hm~2(lambsquarters)>24.22 t DM/hm~2(maize)>15.00 t DM/hm~2(alfalfa).The stem lignin content of three plants increased continuously in the whole growth and development,and the plant stem lignin content plant in maturity period are 0.1746 g/g DM(lambsquarters)>0.1645 g/g DM(maize)>0.1346g/g DM(alfalfa).It's supposed to be selected that the harvesting time with the large biomass and low lignin content for the herbaceous plants when they used as bio-energy raw materials.Therefore,it is better to harvest alfalfa in the green pod period,and harvest maize after the milk stage.Lambsquarters as a kind of potential energy plants has the advantages of larger biomass and competitive.But there is little research about lambsquarters,especially in the field of bio-energy.Thus,utilizing it as biological energy raw materials,further breeding and domestication are required.3)For these samples of the three kind of plants maize,alfalfa,lambsquarters in different development period preprocessed by acid and alkaline,respectively,and determining the residual lignin content in the stem samples after pretreatment.Explore the effects that different pretreatment methods on the different development period of different plants,to provide the basis for bioenergy industry production of different plants.The results as follows:both the acid and alkaline methods have a significant effect for the lignin degradation of the stem samples of maize,alfalfa and lambsquarters in different development periods.Thereinto,the effect of the alkaline pretreatment lignin degradation was better than that of acid pretreatment.And alkaline pretreatment for mazie stem samples is better than that of alfalfa and lambsquarters,the maximum lignin degradation rates of alkaline pretreatment for the three plants are:72%,66%,62%,respectively.The acid pretreatment lignin degradation rates of alfalfa and maize stem are better than that of lambsquarters,the maximum lignin degradation rates are 59%,57%and 52%respectively.There are significant positive correlation among the lignin contents of the untreated stems and the stem samples residual lignin contents of after acid and alkali preteatment(P<0.01).As the growth and development of the plants,lignin deposition also increasing,and the degree of lignin degradation decreased significantly in all the plant stem samples after both of pretreatments(P<0.05).Consequently,choosing the suitable harvest period with low lignin content and high biomass for the plants to reduce the negative effects of lignin for herbaceous energy plants industrial production are extreme important.In conclusion,it is concluded that the lignin deposition of all the three plants were started from the primary xylem and gradually spread along with the growth and development.Maize,alfalfa and lambsquarters should be harvested in milk stage,green pod stage and mature period,respectively.And the lignin should be removed by the alkaline pretreatment for industrial production,which will effectively improve the lignocellulose conversion efficiency. |
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