Allelopathic compounds, thelypterin A and B in the fern Thelypteris normalis

The growth of Thelypteris normalis (C. Chr.) Moxley gametophytes is inhibited under T. normalis sporophytes. Competition for minerals, light, change in pH, or microbial inhibitors were experimentally eliminated as causes of the inhibition. This is the first demonstration of allelopathy between a sporophyte and gametophyte in a fern. Two inhibitors, thelypterin A and B, which were released from the roots of the Thelypteris sporophyte, were isolated and a bioassay for the inhibitors was devised. Thelypterin A gave an Ehrlich-positive reaction indicative of secondary aromatic amines and an ultraviolet absorption spectrum indicative of a heterocyclic ring. The inhibitors affected the growth of Thelypteris, Pteris and Phlebodium gametophytes.