Abstract
The Amazonian water hyacinth, E. crassipes, a Pontederiaceae, is a rarity among higher plants
due to the production of blue colour in its roots in response to nitrogen deficiency in the medium.
Qualitative and quantitative aspects of pigment deposition in the various root regions, from epidermis
to hypodermis, throughout the entire primary cortex, is described. By determining the activity of
three enzymes of the pentosephosphate cycle and the shikimate pathway, in combination with the
successive pigment deposition in the cell qalls, it has been shown that de novo synthesis must occur
and that the pigments are probably anthocyanin-like compounds.
A possible ecological function of the deposition of secondary products in the roots is discussed.
