Ultrastructural Basis and Developmental Control of Blue Iridescence in Selaginella Leaves

The iridescentb lue color of several Selaginellasp ecies is caused by a physical effect, thinfilm interference.P redictionsf or a model film have been confirmedb y electronm icroscopyo f S. willdenowaEnid S. uncinataF. or the latters pecies iridescencec ontributest o leaf absorption at wavelengths above 450 nm and develops in environments enriched with far-red (730 nm) light. This evidence supports the involvement of phytochrome in the developmental control of iridescence.