LEE, DAVID W.*, GEORGE T. TAYLOR, AND ANTHONY K. IRVINE. Department of Biological Sciences, Florida International University, and Fairchild Tropical Garden, Miami, FL 33199. - Structural Fruit Color in Delarbrea michieana (Araliaceae).
The brilliant blue fruit color of Delarbrea michieana (F.
Muell.) F. Muell. (Araliaceae), a Queensland understory rainforest
tree, is caused by a structure (an iridisome) in the epidermal cells.
The iridisome is produced beneath the cell wall and above the
cytoplasm, although its relationship to the plasmalemma is uncertain.
Layers within the iridisomes are of the thickness to interfere
constructively with light at 420-440 nm and produce the blue color.
This structural coloration is unique to this single and uniquely
Australian species, among six taxa in the genus. The iridisome may be
of relatively recent origin. Iridescent blue color production in this
fruit may aid in dispersal by mammals and frugivorous birds and may
allow ripe fruits to continue photosynthetic carbon assimilation.
Key words: constructive interference, fruit, tropical rainforest, ultrastructure