Effects Of Ethylene And Other Growth Regulators On The Growth And Fiber Quality Of Ramie

Boehmeria nivea（L.） is an important textile fiber crop in China,whose fiber fineness is an important index to judge the quality of raw hemp.The finer the fiber is,the higher the fiber count is,the more uniform the yarn strength is,and the better the quality of the finished product is.The development process of ramie fiber is regulated by ethylene.It is of great significance to excavate and use the genes related to ethylene regulating ramie fiber fineness at the transcriptional level for revealing the molecular mechanism of ethylene regulating ramie fiber fineness,and it is of great theoretical and practical significance for ramie fiber quality genetic improvement and high quality cultivation.In this study,ramie germplasm with different fiber fineness was treated with different hormones and foliar fertilizer to explore the effects of hormones and foliar fertilizer on fiber quality.Furthermore,the morphological changes,physiological and biochemical changes and transcriptome changes of ethylene and ethylene inhibitor AgNO₃ on ramie fiber quality were further explored.The main research results are as follows:1.Effects of 5 plant growth regulators,GA,ETH and nitrogen and phosphate fertilizer on yield and quality of ramiePolyamines,BR and SA had a slight promoting effect on the growth and development of ramie.SA,ETH and polyamines all increased the number of ramie fibers and slightly decreased the gum content of the fibers.GA improved the yield and reduced the fiber count.The combination of 200 pp MGA and 2%KNO₃ produced an excellent yield increase of85% compared to the control group and 22% compared to the 200 pp MGA treatment alone.ETH increased the number of ramie fibers and decreased the yield and related traits.Spraying with ETH and medium and high concentration of nitrogen and phosphate fertilizer can increase the fiber count and ensure the increase of yield and optimization of agronomic traits,and the combination of 100 ppm ETH+0.4%KH2PO4 has the best effect.The study confirmed that exogenous ethylene would indeed increase the fineness of ramie fiber,and appropriate combination with phosphate fertilizer could improve the problem of quality improvement but yield decline after ETH spraying.Finally,the treatment concentration of ethephon was determined to be 200mg/L in the follow-up test.2.Effects of ETH and AgNO₃ on yield,dry matter accumulation,fiber quality,phloem cell structure and chemical composition of ramieAfter spraying Sanma for several times,the plant height,stem diameter and yield of ETH group were lower than CK,and the yield of AgNO₃ group was higher than CK.From mong long prior to maturity,total dry matter accumulation type present S growth trend,under the ETH processing ramie long dry matter accumulation rate is accelerated,along with the increase in drug spraying times,ramie dry matter accumulation and distribution in black rod began to show the ETH treatment group of dry matter accumulation is reduced,(quality ratio increases,hemp bone proportion is reduced,AgNO₃ showed the opposite effect when the proportion of raw flax and flax shell increased.The upper fiber fineness of ramie treated with ETH was higher than that of CK in the second flax stage,especially in the mature stage.In the mature stage of Sanma,the fineness of each part was higher than that of CK,and the AgNO₃ treatment group was lower than that of CK.The strength of AgNO₃ in most treatment groups was significantly higher than that of CK,and the strength of ETH in most treatment groups was lower than that of CK.After ETH was sprayed on two kinds of hemp and three kinds of hemp,the changes of chemical composition were obvious at the beginning of black stalk,and the contents of lipid wax,hemicellulose,lignin and pectin decreased slightly,while the content of cellulose increased.The contents of lipid wax and water soluble matter in AgNO₃ treatment group were significantly decreased,while the contents of pectin,hemicellulose and lignin were increased.The phloem fiber layer thickness increased and xylem fiber layer thickness decreased under ETH treatment.3.Transcriptome study of ramie stem bark treated with ETH and AgNO₃In this study,transcriptome sequencing was performed on the upper,middle and lower stem bark of two germplasm ramie at 0 and 5 days after the treatment of ETH and AgNO₃ in the second hemp stage.A total of 61326 Unigenes with the length of N50 of 1666 bp were obtained,and the assembly quality was good.The regulation of ETH on the fineness and quality of ramie fiber involves a large number of functional genes,and the expression patterns of each gene are different in the two germplasms.On the one hand,the ETH for expressed in CK higher some expansin associated with cell wall extending cell expansion,extensin |,XTH gene inhibition effect,make the cut part of PME gene expression,pectin content increased at the same time to control the PH lower expansin activity,make the fiber cell diameter smaller,Reflected in the quality of fineness is greater.On the other hand,ETH inhibited the expression of CESA gene in high fineness germplasm,which reduced the content of cellulose,the main component of cell wall,and the thickness of secondary cell wall.The expression of XTH gene in the upper middle of lowfineness germplasm was inhibited and hemicellulose content was decreased.Inhibit the expression of important genes in several lignin synthesis pathways,reduce the lignin content and reduce the fiber strength.The effect of AgNO₃ on ramie was opposite to the effect of ETH on the whole,and the regulation on low-fineness germplasm was more obvious.AgNO₃ promoted the expression of expansin and extensin genes,and promoted the expression of genes related to cellulose and lignin synthesis,which made fiber cells larger,cell walls thicker and lignin content increased.Finally in the quality of the expression of the fiber cell area becomes larger,fiber fineness becomes smaller,strength becomes larger.