Relatedness Of Neighboring Plants Affects Plant-plant Interaction Of Setaria Italica

Empirical evidence suggests, like animals, some plant species can recognition their kin neighbors, and reduce competition or interference between individuals of close proximity, i.e. positive interaction, and increase fitness. Kin recognition may play an important role in the process of crop plants growth and reproduction. However, so far, little is known about whether crop plants can recognize their kin neighbors. The objective of this study was to explore kin recognition in Sataria italica, the roles of belowground and aboveground competitive cues in the expression of kin recognition in S. italica, and its responses to the different environmental conditions. A field experiment was conducted in the suburb of Shanghai. Plants of S. italica grew with different neighbors (kin, non-kin or stranger), at high or low plant density and high or low soil nutrient level, under the condition of root segregation or root contact. We investigated how neighbor identity and its interactions with root neighbor and plant density and soil nutrient level affected morphology and biomass allocation of S. italica. Results showed,1) Under the condition of root segregation, leaf biomass allocation and stem diameter of plants in kin groups significantly decreased and increased, respectively, suggesting that plants of S. italica in kin groups decreased inter-individual competition (positive interaction), and adapted to the local windy climate; under the condition of low plant density, stem biomass and leaf biomass allocation of plants in kin groups significantly increased and decreased, respectively, compared with non-kin groups; as the plant density decreased, i.e. the distance between neighboring plants increased, plants in kin groups significantly increased stem biomass, while leaf biomass allocation decreased significantly, in contrast, plants in non-kin groups did not show such responses; under the condition of high soil nutrient level, leaf biomass allocation of plants in kin groups decreased significantly compared with non-kin groups.2) Under the condition of root contact treatment, plants in kin groups significantly increased biomass allocation to seeds compared with non-kin groups, suggesting increased fitness in kin groups; at high plant density, plants in kin groups significantly increased seed biomass allocation compared with non-kin groups, as the plant density increased, plants in kin groups decreased leaf biomass allocation, while seed biomass allocation increased significantly, plants in non-kin groups did not show such responses; under the condition of high soil nutrient level, plants in kin groups significantly increased seed biomass allocation compared with plants in non-kin groups, as soil nutrient level increased, plants in kin groups significantly increased biomass allocation to seeds than non-kin groups.3) Plants of S. italica in stranger groups significantly increased biomass allocation to seeds compared with non-kin groups under the condition of both root contact and root segregation treatments, indicating that plants of S. italica in stranger groups may reduce the growth of their neighbors due to the asymmetric competition, thus, allocated more biomass to their reproduction and increased fitness.4) Compared with plants in non-kin groups under the condition of root contact and kin groups under the condition of root segregation, plants in kin groups significantly increased seed biomass allocation and aboveground biomass allocation under the condition of root contact, suggesting plants in kin groups increased fitness and performed better than plants in non-kin groups when belowground interaction existed.5) Kin groups gained the highest group seed biomass allocation under the condition of root contact, which produced 16.5% more group seed biomass than non-kin groups under the condition of root contact, and 28.6% more than kin groups under the condition of root segregation. Our results suggested that plants of S. italica can recognize their kin neighbors, as plants of S. italica decreased competition or interference when planted with their kin neighbors, and increased fitness; belowground competitive cues or the interactions of belowground and aboveground competitive cues played important roles in the course of kin recognition in S. italica; kin recognition was regulated by plant density and soil nutrient level, under the condition of root segregation, lower plant density and higher soil nutrient level may facilitate the ability of kin recognition, while under the condition of root contact, kin recognition tended to be stronger under higher plant density and higher soil nutrient level; kin recognition may increase productivity of S. italica.