Nutrient foraging via physiological and morphological plasticity in three plant species

Abstract

Physiological and morphological plasticity of roots enhance plant nutrient uptake in spatiotemporally heterogeneous soil environments. We examined these two types of plasticity using three plant species (Solidago altissima (L.) Raf., Pinus taeda L., and Liquidambar styraciflua L.). We grew plants in pots (one plant per pot) with equal quantity of fertilizer applied either evenly over the pot surface (H) or on one-quarter of the pot surface (T). A high-concentration 15N-labeled ammonium nitrate solution was injected twice over 48 h before harvest at a random location in H pots, and in either unfertilized or fertilized portion of T pots. Physiological plasticity of N uptake was observed in S. altissima and L. styraciflua. The highest 15N uptake rate for L. styraciflua occurred in H pots (medium level), and that for S. altissima occurred in fertilized portions of T pots (rich level). When low-concentration 15N was added to S. altissima, no differences in uptake were noted among treatments, possibly because of interroot competition. In S. altissima and P. taeda, either morphological or physiological plasticity was strong. In L. styraciflua, both types of plasticity were strong. Total 15N uptake was enhanced when 15N was added to the fertilized patches. Physiological plasticity contributed >70% of enhanced 15N uptake in S. altissima and L. styraciflua.