Adaptive strategies in architecture and allocation for the asymmetric growth of camphor tree (Cinnamomum camphora L.)

The stability-related asymmetry in roots, trunk, and crown is always found as a typical effect of biomechanical design under heterogeneous stimulus environment. However, it appears to be a conflict between the biomechanical principle and the source-sink distance of nutrient allocation strategies when the orientational asymmetry occurs. Adaptive growth strategies associated with biomass and nutrient allocation remain to be explored. This study used both the minirhizotron and harvest methods to test the effect of trunk inclination of camphor trees (Cinnamomum camphora) and found that the asymmetry coefficient of root biomass was - 0.29, showing more root biomass distributed on the other side of trunk inclination. This side had larger surface area and volume of fine roots, the smaller in diameter and the larger in length of the first level roots, higher leaf total nitrogen (TN) and slightly higher root TN content, higher activities of antioxidant enzymes SOD, POD, and CAT in leaves, and lower soluble sugar and protein. The biomass, morphological and physiological characteristics suggest that trees may follow both the biomechanical design and source-sink distance of nutrient allocation strategies. The research results expand the connotation of root-shoot balance in the orientational allocation of biomass and physiological responses.