Change of root morphology in intercropping systems of wheat and faba bean under different phosphorus levels and its relationship with endogenous hormones

We examined the correlation between changes of root morphology and endogenous hormones in intercropping systems of wheat and faba bean under different phosphorus levels by hydroponics. Compared with monocropping wheat (MW), the intercropping of wheat and faba bean (W∥F) significantly increased root length of wheat, reduced root average diameter of wheat, and increased root surface area under the condition of 1/2P (low P) level. At the conventional phosphorus level, intercropping significantly reduced root average diameter of wheat, and increased root length and root surface area. Compared with monocropping faba bean (MF), W∥F significantly promoted the growth of faba bean root and increased root surface area of faba bean. At the level of 1/2P, intercropping significantly increased the content of auxin (IAA), abscisic acid (ABA), sali-cylic acid (SA) and jasmonic acid (JA). At the conventional phosphorus level, intercropping could significantly increase the content of IAA, ABA and JA in wheat root, while no significant difference in the SA content of wheat root between monocropping and intercropping wheat was found. Intercropping could increase the content of ABA and SA in faba bean roots, but did not affect IAA and JA contents of faba bean roots. There was no significant correlation between the contents of endogenous hormones (IAA, ABA, SA and JA) and root morphology (root length, root average diameter and root surface area) of wheat and faba bean roots in wheat or faba bean monocropping system. In wheat and faba bean intercropping system, there was a positive correlation between IAA contents of wheat and faba bean and their root length and root surface area. W∥F enhanced IAA of wheat and faba bean root, which was an important factor driving the change of root morphology in the intercropping system of wheat and faba bean.