Effects Of Nitrogen Fertilizers On Agronomic Traits,Cell Wall Compositions And Biomass Enzymatic Digestibility In Rice

Rice is a major food crop with large biomass residues for biofuels and bio-chemicals in China.Plant cells walls are majorly composed of cellulose,hemicellulose and lignin,and they play important roles in plant morphogenesis,carbohydrate metabolism and environmental stress responses.Plant biomass yield and composition is affected by a number of environmental factors,such as the availability and conversion of solar energy,water and nutrients.Among the nutrients,nitrogen is most frequently the main limiting factor for plant growth and development and is an essential component of fertilizers used to increase the productivity of agricultural crops.Nitrogen is an essential element for plant growth,development and reproduction.It is also a major component chlorophyll and amino acids.Despite that N supply is critical to increasing grain yield and biomass production in rice,little is yet reported about its effects on plant cell wall compositions and wall polymer features,as well as biomass enzymatic saccharification for biofuels.In this study,seven distinct N fertilizer treatments were performed in two rice cultivars in experimental fields,then we observed major agronomic traits and determined cell wall compositions and biomass enzymatic digestibility due to various physical and chemical pretreatments.As a result,seven nitrogen fertilizer treatments could largely increase grain yields of seeds and biomass production of straws in two rice cultivars,compared with control(with basal fertilizers only).By comparison,the N fertilizer treatments led much higher cellulose contents and lower silica levels in straws,but hemicelluloses and lignin exhibit variations among different N treatments.Under different chemical(Na OH,Ca O,H2SO4)and physical(hot water)pretreatments,two rice cultivars supplied with N fertilizers exhibited much higher hexose yields released from biomass enzymatic hydrolysis,as well as higher bioethanol production from yeast fermentation,as compared to the control.Notably,cellulose DP values and hemicellulosic Xyl/Ara ratios were much reduced in the straw biomass residues of two rice cultivars supplied with N fertilizers,whereas other wall polymer features(cellulose Cr I,three monomers of lignin)showed a variation.Furthermore,correlation analyses indicated that cellulose DP,Xyl/Ara and silica level are the major factors negatively affecting biomass enzymatic digestibility and bioethanol productivity in rice.In conclusion,the N fertilizer supplies could not only largely increase grain yields of seeds and biomass production of straws,but also significantly alter cell wall composition and wall polymer features for enhancing biomass enzymatic digestibility and biofuel production in rice.Hence,it also provides the strategy for enhancing both agricultural food production and biomass-based products in the future.