Clonal Integration and Root Morphological Plasticity of Indocalamus latifolius Under Heterogeneous Phosphorus Environments

Owing to clonal integration and morphological plasticity, clonal plants generally exhibit higher fitness in nutrient-heterogeneous environments. Indocalamus latifolius (Keng) McClure is a clonal plant with considerable economic value in China. However, the mechanisms of clonal integration and morphological plasticity in I. latifolius under phosphorus (P) heterogeneous conditions remain unclear. To clarify the mechanisms, a pot experiment was performed with I. latifolius clonal fragments consisting of mother ramet, rhizome, and daughter ramet. The experiment used a two-factor design with the following six treatments: P addition regime (uniform P addition, localized P addition to mother ramets, and localized P addition to daughter ramets) and rhizome status (connection vs. severance). Biomass allocation, root morphological plasticity, and the allocation pattern of P and non-structural carbohydrates were determined. The results showed that localized P addition increased the biomass of ramets growing in high-P patches and the total biomass of the clonal system compared with uniform P addition. Under three P supply regimes, rhizome connection significantly improved the biomass and P accumulation of daughter ramets relative to rhizome severance. In heterogeneous P environments, rhizome connection facilitated the proliferation of finer root and raised the soluble sugar concentrations in belowground tissues of ramets located in low-P patches compared with rhizome severance. In conclusion, resource allocation within the I. latifolius clonal system is prioritized toward daughter ramets and ramets in high-P patches. Clonal integration can promote compensatory root growth and morphological modification in ramets located in low-P patches. Localized P addition to mother ramets combined with the maintenance of rhizome connectivity between mother and daughter ramets is more conducive to the overall growth of the clonal system.