N, P, and C stoichiometry of Eranthis hyemalis (Ranunculaceae) and the allometry of plant growth.

We report the nitrogen (N), phosphorus (P), and carbon (C) stoichiometry for each of the five organ-types (leaves, aerial stems, reproductive organs, roots, and tubers) of 17 actively growing Eranthis hyemalis plants differing in size (as measured in g C). We also report the N, P, and C stoichiometry of 20 winterized tubers, which are the only perennial organs of this species. Comparisons between whole-plant and winterized N/C and P/C levels indicate that N was resorbed from aerial organs and stored in tubers by the end of the growing season. Leaves were substantial reservoirs for N and P. With few exceptions, N scaled isometrically with respect to C for each organ-type, whereas P scaled as the 3/4 power of C. Thus, N is proportional to P(3/4), which is proportional to C regardless of organ-type. Additionally, annual growth rate G of shoots (leaves and aerial stems) scaled as the -3 power of leaf N/P quotients such that G was proportional to the 3/4 power of leaf P. We suggest that these scaling relationships (together with previously reported allometric trends across herbaceous species) show that growth is constrained by organ-specific N and P allocation patterns (presumably to proteins and ribosomes, respectively).