Structural Fruit Coloration in Delarbrea michieana (Araliaceae).

The brilliant blue fruit color of Delarbrea michieana (F. Muell.) F. Muell. (Araliaceae), a Queensland understory rain forest tree, is caused by iridisomes (structures) in the epidermal cells that are produced beneath the cell wall and probably outside of the cytoplasm. Layers within these iridisomes are of such a thickness that they interfere constructively with light at 420-440 nm and produce the color. Such color production may aid in attracting mammals and large frugivorous birds (which may disperse the fruits) and may also allow ripe fruits to continue photosynthetic carbon assimilation.