Seedling adaptive characteristics of Phragmites australis to nutrient heterogeneity under salt stress using a split-root approach

Coastal wetlands are highly heterogeneous due to their location between land and ocean. Clonal plants living in coastal wetlands can adapt to nutrient and salinity heterogeneity through clonal integration. However, little is known about how the single clonal ramet with fine roots adapts to nutrient heterogeneity within the microhabitat. Pot control experiments with 12 treatments were conducted to evaluate adaptive characteristics of Phragmites australis seedling to nutrient heterogeneity under salt stress. The results showed that under homogeneous nutrient treatment, 1.5% salt significantly reduced plant height and tiller number in P. australis and depressed the effect of nutrients on the leaf length, width and internode length. The homogeneous nutrient gradients had no significant effect on the aboveground biomass of P. australis in 1.5% salt condition. However, under 1.5% salt treatment, heterogeneous nutrient significantly reduced the underground biomass, including rhizome and adventitious root biomass. The root-shoot ratio was higher under homogeneous nutrient treatment than heterogeneous treatment with the same total nutrient amount applied. However, the accumulation of total nitrogen and total phosphorous in the stems and leaves of P. australis did not show significant differences, except that without salt stress, heterogeneous treatment decreased the total nitrogen content of stems and leaves at low nutrient levels. The results demonstrated a preference for homogeneous nutrient conditions in saline micro-environments in P. australis; however, when encountering heterogeneous soil nutrient environments, plants can maintain their nutrient requirements and even promote growth through physiological plasticity