Effects of fertilization on resource allocation of two exotic plants of Salvia

Abstract [Objective] Comparison of resource allocation strategies in terms of growth,reproduction and defense under different nutrient conditions between two exotic plants of the Salvia tiliifolia and Salvia splendens, to understand the invasion mechanism of S. tiliifolia. [Methods] By pot experiments, two exotic plants of Salvia were chosen as experimental materials. Three nutrient gradients [control (0 g), low fertilizer (2 g), and high fertilizer (4 g)] were established. Indexes of growth, reproduction, physical defense, chemical defense, and content of nutrient substances were measured. [Results] (1) The biomass, nutrient content, and chemical defense capability of flowers in both species followed the order: High fertilization > low fertilization > control, while the physical and chemical defense capabilities of leaves followed the opposite order: Control > low fertilization > high fertilization. (2) Under the same condition, S. tiliifolia exhibited higher plant height, leaf number, flower number, and total biomass compared to S. splendens, allocating 43%-52% of its total biomass to sexual reproduction. The physical and chemical defense indices of leaves were also higher in S. tiliifolia than in S. splendens, but the chemical defense indices of flowers and nutrient content were lower. The leaf of S. tiliifolia showed higher content of chemical defense substances than flower, and the S. splendens was the opposite. [Conclusion] Under conditions of abundant resources, both species reduce investment in leaf defense and increase investment in growth and reproduction. S. tiliifolia focuses on leaf defense, while S. splendens focuses on flower defense.