Root Parasitism of Castilleja Coccinea

Abstract

The showy Indian paint—brush, Castilleja coccinea (L.) Spreng., is photosynthetic, but its roots produce haustoria that penetrate the roots of plants growing near it. It interacts with those plants as a parasite; unless it penetrates them, it does not mature beyond the seedling stage, and once it does it significantly lowers their dry weight. Phosphate, sulfate, and fructose are known to move across the haustoria rapidly, but what the plant actually uses from its hosts is not known. Artificial feeding of common vitamins, phytohormones, and respiratory substrates does not take the place of a host. C. coccinea will attack plants of many vascular species, including several that do not occur in its range.