Table 1.

Nomenclature.

interspecific scaling law	a scaling power-law to show the allometric relationship between a biologic variable and body weight. A general format of the interspecific law is written as: A = K · Ba, where A refers to the shape, anatomy, or physiological parameters among species, B body weight, K the scaling coefficient and a the scaling exponent.
Y = Kmetabolism · B3/4	the allometric 3/4 scaling law of metabolism (i.e. an interspecific scaling law), where ‘Y’ is the metabolic rate and ‘Kmetabolism’ is the corresponding scaling coefficient.
the stem–crown units	a vessel in a tree is selected as a stem and the subtree distal to the stem down to the terminal vessels is defined as a crown. A tree structure consists of many stem–crown units, as shown in figure 1a. In a stem–crown unit, the crown volume, Vc, is the sum of the intravascular volume of each vessel from the stem to the terminal vessels and the crown length, Lc, is the sum of the length of each vessel from the stem to the terminal vessels.
intraspecific scaling law	a scaling power-law to dictate the design of cardiovascular trees within a given species. A general format of the intraspecific law is written as: A = K · Ba, where A and B refer to morphometric or physiological parameters in an integrated system of stem–crown units, K the scaling coefficient and a the scaling exponent.
	the length–volume scaling law (i.e. an intraspecific law), where ‘Klength–volume’ is the scaling coefficient of the length–volume scaling law.