Study of the effect of volatile substances from cereal roots

We traced the liberation and biological effect of volatile substances released from the roots of cereals,i. e. barley, wheat, rye and oats, on seedlings of the same and other plant species. Experiments were carried out in a closed glass apparatus with a static or circulating atmosphere in which the CO₂ and O₂ were permanently absorbed and supplemented, respectively. In some experiments the air was bubbled through water or through solutions of boric acid, barium hydroxide and potassium permanganate. The roots of all four cereals tested released volatile substances with a biological activity which appeared to be non-specific with respect to plant species. The effect of volatile substances was partially decreased by bubbling through water, barium hydroxide and boric acid and was completely removed after passing through the solution of potassium permanganate. Volatile substances liberated from roots of barley inhibited elongation of roots and coleoptile, decreased SH-group content and caused excessive formation of root hairs as well as inhibition of both dry matter production and respiration of roots of rye seedlings. Ethylene was found in the atmosphere of experimental vessels.