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Scientia Silvae Sinicae ›› 2021, Vol. 57 ›› Issue (9): 42-51.doi: 10.11707/j.1001-7488.20210905

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Effects of Exogenous IAA on Stem Secondary Growth of Pinus massoniana Seedlings

Zijing Zhou1,Fuhua Fan1,*,Xianwen Shang1,Huijuan Qin1,Conghui Wang1,Guijie Ding1,Jianhui Tan2   

  1. 1. Institute for Forest Resources and Environment of Guizhou Province Key Laboratory of Forest Cultivation in Plateau Mountain of Guizhou Province College of Forestry, Guizhou University Guiyang 550025
    2. Guangxi Zhuang Autonomous Region Forestry Research Institute Nanning 530002
  • Received:2021-04-21 Online:2021-09-25 Published:2021-11-29
  • Contact: Fuhua Fan

Abstract:

Objective: Pinus massoniana is a unique fast-growing tree species in China and is one of the main afforestation tree species in southern China, which has high economic and ecological value. Auxin has a significant effect on the secondary growth of plants. An in-depth study on the secondary growth of the stem of P. massoniana can provide theoretical basis for breeding new varieties of P. massoniana with fast growth and high yield. In this study, two-year-old P. massoniana seedlings were sprayed with different concentrations of IAA. The effects of exogenous IAA on the secondary growth of P. massoniana seedlings were analyzed in combination with physiological, biochemical, morphological traits and anatomical structures and transcriptome changes. This study could lay a foundation for elucidating molecular regulation mechanism of stem secondary growth of P. massoniana seedlings. Method: Two-year-old P. massoniana seedlings were sprayed with different concentrations of IAA(0, 1, 50, 100 mg·L-1). After 160 days of treatment, growth traits, anatomic structure, physiological and biochemical properties were measured. The differentially expressed genes were identified by high-throughput transcriptome sequencing, and analyzed by GO and KEGG. Result: IAA treatment significantly promoted the ground diameter, cell growth(xylem and phloem thickness and xylem cell layers), physiological components of wood(lignin, cellulose and hemicellulose), endogenous hormone contents(auxin, gibberellin and brassinolide) of two-year-old P. massoniana(P < 0.05). Six cDNA libraries of CK and IAA were sequenced by Illumina sequencing, 778 differentially expressed genes(including 482 up-regulated genes and 296 down-regulated genes) were obtained. GO analysis showed that these differential genes were mainly involved in 22 categories of cell components, molecular functions and biological processes, and KEGG analysis showed that they were involved in 64 different pathways. Differentially expressed genes related to secondary growth of P. massoniana were screened, such as BRL1, GASA6, CAD, CESA2, etc. Conclusion: IAA treatment changes the content of endogenous hormones, promotes cell division, increases the accumulation of lignin, cellulose and hemicellulose. Thus it promotes the secondary growth of P. massoniana. Our results provide a solid basis for revealing the mechanism of hormone regulation of secondary growth of P. massoniana.

Key words: Pinus massoniana, IAA, secondary growth, transcriptome

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