Scaling of phloem hydraulic resistance in stems and leaves of the understory angiosperm shrub Illicium parviflorum.

The overall architecture of the phloem tissue in this understory angiosperm shrub scales in a manner consistent with taller trees that make up the forest canopy. Thus, the evolution of larger sieve plate pores in canopy-dominant trees may have played a key role in allowing woody angiosperms to extend beyond their understory origins.