| To study the adaptability of dioecious plants morphological structures to reproductive function,the female and male secondary xylem of the 31-year-old stem of Ginkgo biloba L.and the 5-year-old stem of Salix babylonica L.were used as experimental materials in this study.The sexual dimorphism of tracheary elements were studied by wood section method and segregation method.The tracheary elements were formed by the division,differentiation and development of cambium cells,in order to explore the causes of the sexual dimorphism of tracheary elements,the RNA-seq technique was used to analyze the differences in cambium transcriptomes of two species.The main results showed as follows:1.The annual ring width of female plants of G.biloba and S.babylonica were larger than those of male plants in the same year.The female of G.biloba was 0.34%(31st year)to 25.91%(6th year)larger than that of the male,while the female of S.babylonica was 1.49%(3rd year)to 12.19%(1st year)larger than that of the male.2.In G.biloba,the early wood tracheid length,width and lumen diameter of the female was 3.03%,5.34% and 6.18% larger than that of the male,the late wood tracheid length,width and lumen diameter of the female was 2.57%,5.57% and 6.55% larger than that of the male,the wood ray density was 12.27% greater than that of male plants(P<0.05).In S.babylonica,the vessel length,width,lumen diameter and density of female plants were 8.20%,4.25%,4.39%,and 22.89% larger than those of male plants,the tracheid length,width,and lumen diameter were 7.28%,10.11% and 14.77% larger than those of male plants,the wood fiber length,width and lumen diameter were 9.34%,9.41% and 13.81% larger than that of the male,and the wood ray density was 10.09% larger than that of the male(P<0.05).3.In the same annual ring of G.biloba,the tracheid length,width and lumen diameter of female plants were 1.09% to 7.43%,1.47% to 7.97% and 1.96% to 13.2% larger than those of male plants,the length-width ratio and wall-lumen ratio were 0.40% to 2.22% and 3.47% to 29.70% smaller than that of male plants(P<0.01).In the same annual ring of S.babylonica,the vessel length,width,length-width ratio and lumen diameter of females were 8.90% to 15.56%,1.74% to 3.26%,5.70% to 13.93%,and 1.82% to 3.44% larger than those of males(P<0.01),the tracheid length,width,length-width ratio,lumen diameter and lumen-diameter ratio were 5.48% to 18.36%,8% to 13.01%,1.52% to 8.80%,12.27% to 18.91%,and 4.42% to 6.85% larger than male plants,and the wall-lumen ratio was 14.62% to 22.96% smaller than that of male plants(P<0.01).4.A total of 1 466 differential genes were screened out from G.biloba,of which 844 genes were up-regulated,the gene expression level was 50.10% to 100% higher in females than in males,and 622 genes were down-regulated,the gene expression level was 50% to 100% lower in female plants than in male plants.While there were a total of 1 225 genes expressed differentially in S.babylonica,including 773 up-regulated genes,the gene expression level was 50.10% to 100% higher in female plants than in male plants,and 452 down-regulated genes,and the gene expression level in female plants was 50.10% to 100% lower than in male plants.5.The expression of IAA12 genes in male vascular cambium transcriptomes of G.biloba were 66.79% higher than in female plants,while the expression of IAA4 genes in female vascular cambium transcriptomes of S.babylonica were 65.84% higher than in male plants.The above results showed that(1)in different time scales,morphological structures of tracheary elements of two plants stems had sexual dimorphism,and were adapted to their reproductive function.This not only provided strong structural evidence for the existence of primary sex characters of plants,but also enriched the contents of secondary sex characters of plants,and provided clues for the early sex identification of female and male plants.(2)the sexual dimorphism of tracheary elements in morphological structures of two species were mainly the result of gene regulation. |
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