Rape is the world's third largest oil crop, an important source of high-quality vegetable oil and feed protein, and has become one of the most valuable trade agricultural products. Rape has strict water requirements throughout its growth stages. With the occurrence of global warming and heavy rainfall events, the rape production environment has deteriorated. The alternating occurrence of drought and flooding has a significant impact on the growth process and metabolic process of rape, and ultimately reduces the yield and quality of rape.‘Sow once, all seedlings’is the basis for high and stable crop yields. The water condition after sowing of rapeseed largely determines the number of seedlings. The effect of water conditions in each growth stage after seedlings in rape production should not be underestimated, which determines the ultimate production benefit of rapeseed.In the process of water stress, the rape root system preferentially senses drought (flooding) signals, and a series of physiological reactions such as stomata closure,photosynthesis weakened and osmotic adjustment occur in the upper part of the plant. The above-ground and underground parts simultaneously activate corresponding mechanisms to combat water stress,and the existing research has not conducted in depth analysis of rape root-shoot interaction.