No notable tragedy of the commons was found in Monkhead or in 92-46
Pot partitioning treatments allowed us to exclude confounding effects of rooting space when testing plant responses to neighbours (Semchenko et al. 2007). We predicted that old Monkhead would have a greater expression of the tragedy of the commons than modern 92-46. However, our results showed that most allometric relationships were not affected by the presence of roots from an intra-variety neighbour (Table 3, Appendix 1, 2), which suggested stable allometric relationships in wheat crop when confronted with root competition. However, in low fertility treatments, old Monkhead did show some tragedy of the commons, with slightly increased allocation to stem&leaf biomass whilst reduced seed allocation in mesh partition compared with plastic partition (Table 3, Appendix 1c and e). This slightly allometric plasticity due to competition was also found in a research in Senecio vulgaris(Weiner, 2009). Anyway, as the magnitude of ‘the tragedy of the commons’ was small, they might not have ecological and agricultural significance. However, in a recently research, both Monkhead and another modern variety showed significant root proliferation in the presence of neighbour’s roots and the response was much higher in Monkhead (Zhu et al., 2019). More researches using more varieties were needed to examine the universality of this tragedy of the commons. Moreover, old Monkhead increased relative stem&leaf allocation in the presence of root competition, indicating the capacity of neighbour-identity recognition via the phytochrome system (Smith 2000) or root exudates (Dudley and File 2007; Chen et al. 2012; Fang et al. 2013; Kong et al. 2018).