Universal scaling of respiratory metabolism, size and nitrogen in plants

Evolution: growing apart It's almost a law of nature: as animals and plants vary in size, their metabolism varies (or ‘scales’) at a predictable but different rate, a phenomenon called allometry. Less certain is the precise rate at which the two quantities vary. Classical theory derived from simple geometry suggests that if mass increases by a given amount, metabolism increases by two-thirds as much. However, much recent work points to a scaling exponent of around three-quarters. This has opened up an enormous front of research and debate, and into the fray step Reich et al. who, in an unprecedentedly comprehensive survey of plant metabolism, overturn the whole notion of allometric scaling. Metabolism in plants varies not allometrically but isometrically, in one-to-one step with changing mass. This underlines fundamental differences between animals and plants, with plants controlled largely by biochemistry and animals largely by vascular networks.