Fig. 1.

The stoichiometry-based and ecology-based perspectives (Table 1) often suggest contradicting predictions of the relationships between plant genome size (1C or 1Cx value), guanine–cytosine (GC) content, and plant tissue nitrogen (N), phosphorus (P), and N : P ratio. Black lines indicate hypothesized trends for the central tendencies, whereas grey lines indicate hypothesized trends in lower, middle and upper quantiles. (A) DNA is an N- and P-demanding biomolecule, and thus its content (1C value) can be positively correlated with plant tissue N and P, while it can be negatively linked to plant N : P because DNA is a relatively P-rich biomolecule with low N : P. The stoichiometry-based perspective also predicts positive links of GC content to plant N and N : P, because GC pairs have more N atoms in their molecules than AT pairs. We also expected that the proposed relationships would be more pronounced in upper quantiles, i.e. in plants with large genomes and GC-rich nucleotide compositions that can contribute more to the overall plant N and P pools than small genomes or GC-poor nucleotide compositions. (B) The ecology-based perspective suggests negative links of genome size to plant N and P and a positive link to N : P. Stress-tolerant species are typically slowly growing and conservative, with larger genomes but lower N and P, and higher N : P compared to fast-growing and acquisitive ruderals. Ecological strategies are also connected to GC content as P-poor (but with high tissue N : P) stress tolerators tend to have higher GC content. The strength of the proposed relationships can vary across quantiles; for example, small genome species (lower quantiles) might allocate more P and N to RNA and proteins, respectively, to promote fast growth.