Effect of different root separation methods on kin recognition and selection of Stylosanthes guianensis ‘Reyan No. 5’

This study assessed the effects of different root separation methods on kin recognition and selection of Stylosanthes guianensis ‘Reyan No. 5’. Three root separation methods were used: (i) no separation, (ii) nylon mesh, and (iii) plastic film. ‘Reyan No. 5’ was grown alone and separately with three cultivars ‘Reyan No. 2’, ‘Reyan No. 21’, and ‘Reyan No. 24’, in pot experiments. Changes in the morphological characteristics (plant height, number of branches, root length, and number of lateral roots) and biomass allocation (aboveground biomass, underground biomass, total biomass, leaf-stem ratio, and root-shoot ratio) were recorded. The results showed that the growth indices of ‘Reyan No. 5’ changed significantly under different root system separation methods. The aboveground, underground, and total biomass phenotypic indices showed a significant (P < 0.05) trend of no separation between roots < nylon mesh separation between roots and plastic film separation between roots. With no root separation, the plant height, the number of branches, aboveground, underground, and total biomass indices, and the leaf-stem ratio of ‘Reyan No. 5’ increased significantly (P < 0.05) when it was grown with ‘Reyan No. 24’. The number of branches and lateral roots, underground and total biomass, and leaf-stem ratio improved significantly (P < 0.05) when it was associated with ‘Reyan No. 21’. The aboveground and total biomass, and leaf-to-stem ratio of ‘Reyan No. 5’ was significantly (P < 0.05) reduced when it was grown with ‘Reyan No. 2’. Compared with the control group, the other growth indicators were not significantly different. The relative interaction index showed that the growth of ‘Reyan No. 5’ was promoted when it grew with ‘Reyan No. 21’ and ‘Reyan No. 24’, with ‘Reyan No. 24’ having a stronger effect. The growth of ‘Reyan No. 5’ was inhibited when grown with ‘Reyan No. 2’. These results suggest that ‘Reyan No. 5’ could identify the relationship between neighboring plants and itself through root exudates and then adopts a cooperative response strategy of controlling its growth with neighboring closely related plants.