Chemical induction and repression of Haustoria in Orthocarpus Purpurascens (Scrophulariaceae)

Abstract

A preliminary survey of compounds that induce haustoria in the hemiparasite Orthocarpus purpurascens suggests that cellulose fibre is one source of the active, water soluble factor(s). Haustoria are induced by extracts of soya bean seeds, flax seeds, plant roots, cotton string, cotton, paper towel, tissue paper and yeast extract. Sugars, hormones, nitrogenous compounds, microbial exudates, and citric and ascorbic acid do not induce haustoria. Citric acid has a positive synergistic affect in the presence of an inducing factor.Terramycin applied to seedlings 3 days of age had a detrimental effect on root development, while penicillin did not. Penicillin reduced the numbers of haustoria formed between 19 and 25 days of age. The combined use of penicillin and inducing factors may provide an excellent experimental system for determining the temporal and developmental pattern of haustoria formation. © 1978 Annals of Botany Company.