| Microbial dyeing of wood is a new method of wood color blending which is based on the biomass properties and multi-scale pore structure characteristics of wood and microbial living habits,by controlling the living behavior of microorganisms on wood,wood can produce color and pattern effect with natural characteristics,improve the quality of wood utilization.It belongs to the category of wood biological processing technology and has a good prospect.In this study,the Lasiodiplodia theobromae was used as the main dyeing subject to carry out microbial dyeing on poplar wood（Populus euramevicana）by the reverse thinking of microbial discoloration control of wood.On the basis of optimizing the normal living conditions of Lasiodiplodia theobromae,the inducible substances that promote the rapid biosynthesis of melanin and produce specific expression in the synthesis pathway were used to realize the induction of the color and yield of Lasiodiplodia theobromae secretion pigment（hereinafter referred to as induced color and induced production）and analyze the induced growth and secretion characteristics of Lasiodiplodia theobromae.Based on the culture characteristics of Lasiodiplodia theobromae induced in vitro,the induced infection mechanism of Lasiodiplodia theobromae on different sections of poplar was analyzed,and the directional induction of color and pattern of poplar by Lasiodiplodia theobromae was explored.The induced melanin by separating was analyzed in structure and used to dye poplar wood.The main conclusions are summarized as follows:（1）Tyrosinase and tricyclazole had significant inducing effects on Lasiodiplodia theobromae in PDA medium.The secretion color of tricyclazole was reddish-brown after induction,and the crude melanin content after induction was up to 3.47 mg/m L.After 20 days,the average efficiency of 100mg/L tricyclazole was 0.083 mg/（m L*d）.5 mmol/L Cu2+had a significant inhibitory effect on the growth and secretion of Lasiodiplodia theobromae.The melanin of Lasiodiplodia theobromae is a kind of isomelanin,which mainly contains benzoquinone structure and aliphatic structure polymer;The melanin of Lasiodiplodia theobromae had good solubility under alkaline conditions,with a relative crystallinity of 81%-84%,mass loss rate of 44.7%-49.5%and a particle size of 50-300 nm.（2）The induced infection of the Lasiodiplodia theobromae in poplar wood was directional,and the infection path showed a three-dimensional structure.The fungus invaded the wood through the tube hole of the tube on the axial direction.Under the induction of tyrosinase,the maximum infection depth reached 20 mm at 20 d,and the infected area accounted for 20%of the cross-sectional area,and the infected area at 40 d up to 70%.However,in the lateral direction,the intrusion into the wood was mainly through the pits in the duct and wood ray cells.The infection thickness of the chord section and the diameter section was about 0.6-1 mm at 40 d.（3）The poplar wood infected by Lasiodiplodia theobromae showed a natural and stable color and had little effect on mechanical strength.Under the induction of tricyclazole,the poplar wood infected by Lasiodiplodia theobromae showed a reddish-brown color.The chromatic aberration was greater than 44.5 NBS after 30 d of cross-section infection,with natural color transition and the gradually changed boundary.After 40 days of infection with Lasiodiplodia theobromae,the 100 h light-resistant chromatic aberration of poplar wood was below 1.5 NBS,and the 4 h water-washing chromatic aberration was below 3.0 NBS,and the crystallinity of poplar wood reduced by 3.4-4.9%.Among them,the weight loss rate of dyed poplar wood decreased by 0.43%-3.09%,and the contact angle increased by 3.1-15.85°.The loss rate of tensile modulus was less than 2%after 20 days of infection,and the change range of compressive strength was-2.57%-6.8%after 40 days of infection.（4）Inducing（tyrosinase,tricyclazole）and inhibiting(Cu2+)substances can achieve the targeted infection of Lasiodiplodia theobromae in poplar wood.The first 5 d achieved the effective regulation and control of Lasiodiplodia theobromae by inducing substances and inhibitors and activities according to the preset target pattern trajectory.After 10 d the induction effect remained unchanged but the inhibitory substance’s inhibition of Lasiodiplodia theobromae decreased.The infestation effect was strengthened and the chromatic aberration between the inhibition area and the induction area decreased.The pattern similarity of 20 d directional infestation decreased by 1.12-6.04%.In the meantime,the oblique line induction kept well in the trajectory growth of the target pattern,and the similarity reached 46.56%.（5）The melanin of Lasiodiplodia theobromae had a good dyeing effect on poplar.The contribution of the dye concentration to the dye uptake rate of poplar veneer after dyeing for 30 min was reduced,and the L*a*b*chromaticity value of poplar veneer with the largest chromatic aberration after dyeing for 2 h was（67.108,10.538,34.554）.After dyeing the wood block for 10 h,the dye concentration had a weaker effect on the dye uptake rate of poplar block,and the L*a*b*chromaticity value of the poplar wood after dyeing for 40 h was（51.142,12.637,28.717）.The melanin of the tyrosinase induced group showed a dense and granular distribution on the surface of the poplar wood block.The melanin dye of the tricyclazole induced group was prone to cluster aggregation during the dyeing process,and the color fastness to washing was poor. |
