Study challenges metabolic scaling law

A paper in this week's Nature claims that plants do not show the same mass-to-respiration ratio widely documented in animals. According to Peter Reich of the University of Minnesota and his colleagues, plant mass scales in a one-to-one ratio with respiratory metabolism, while most animal respiration is proportional to an animal's mass raised to the 3/4 power. The authors claim that this discrepancy arises because plant respiration is constrained by nitrogen availability, rather than by delivery of nutrients through vascular networks.Reich and his co-authors make a "strong argument" that respiration rate is not dependent on the delivery of metabolites through plant vascular systems, said John Damuth of the University of California, Santa Barbara, who was not involved in the study.But not all scientists agree. Brian Enquist of the University of Arizona in Tucson and his colleagues have theorized that metabolism?as well as other physiological processes?scale in a consistent...