Strigolactone regulates plant architecture by inhibiting lateral branch growth in Quercus mongolica seedlings

Mongolian oak (Quercus mongolica) is an important timber species in northeast China, but overdeveloped lateral branches during the seedling stage often result in poor plant architecture and reduce the growth potential. Strigolactones (SLs) were proposed to play an important role in plant architecture by inhibiting the growth of lateral branches; however, there is no knowledge on the strigolactone effects in Mongolian oak. In this study, 0.3, 3, 10, and 30 mg/L of GR24 (analogue of SLs) and 1 mg/L Thidiazuron (TDZ) were applied to Mongolian oak seedlings by the lanolin method. All GR24 treatments significantly reduced the number and biomass of lateral branches; in addition, the length increment of lateral branches was decreased by 3, 10 and 30 mg/L GR24. In addition, the auxin content in lateral branches was significantly increased by the 10 mg/L GR24 treatment, which might be one of the main reasons for the inhibition of lateral branch growth. Increased sucrose content in apex, combined with a decrease of sucrose content in lateral branches, further demonstrated the important role of GR24 in inhibiting lateral branch growth.