Soybean triggers tomato root horizontal asymmetry by modifying capture of P rather than N under low nutrient condition

Plants alter root placement patterns to respond nutrients and neighbors, but whether neighbors influence the root architecture by modifying the availability of nutrients is still unclear. Here we aimed to screen intercropping plants cause changes in tomato root architecture and explore the role and potential activation pathways of N and P nutrients.

We carried out the experiments of tomato-neighbor interactions to survey root plastic responses of target tomato seedlings and root placement patterns to intercropping soybean under different P or N levels. In addition, we investigated the effects and physiological mechanisms of intercropping soybean on P capture of tomatoes.

The intercropping soybean changed the horizontal symmetry of tomato roots, the dry weight and total root length of tomato roots in the ‘Toword’ region were significantly higher than those in the ‘Away’ region, while other intercropping plants did not. P rather than N levels, significantly affected the tomato root placement patterns in soybean intercropping systems. Under phosphorus deficiency condition, tomato roots showed a tendency to soybean. This phenomenon disappeared when the P supply increased. Under low P condition, intercropping soybean significantly increased P concentration of tomato plants and rhizosphere soil available P content. Compared with tomatoes, soybean roots secreted more acid phosphatase, protons and organic acids.

Soybean triggered tomato root horizontal asymmetry through modifying tomato P rather than N capture mediated by root exudates under low nutrient condition, which contributes to the selection and application of tomato cultivation models in low input agriculture.