Influences of brassinolide synthesis gene DWF1 and DET2 on xylem formation in Populus tomentosa

Brassinolides are important for plants growth and development. Transgenic poplars with brassinolides biosynthesis genes GhDWF1 and GhDET2 were selected and analyzed about the growth，microstructure of xylem and cell wall composition. It was found that DWF1 and DET2 had influences on xylem formation and cell wall composition in Populus tomentosa. Transgenic poplars had higher xylem area，smaller cells and thicker cell walls than the control，which may affect cell division and lateral expansion. Pits on vesselswere enlarged，which may affect water transport in poplars. Contents of acidic pectin increased，and contents of cellulose decreased in transgenic poplars， which may change frame structures of cell wall. Transgenic poplars with GhDET2 had higher lignin content and high S-lignin ratio， which may cause chemical degradation easily，while transgenic poplars with GhDWF1 had lower lignin content，higher G/S ratio and smaller S-lignin content .