Abstract
The effect of growth inhibitors from peach roots on the activity of β-cyanoalanine synthase was investigated. A positive correlation was found between the condensed tannin content and the inhibition of β-cyanoalanine synthase activity in the fractions of extract of peach roots. Ethyl-acetate-soluble neutral fraction, which showed the highest content of condensed tannins and the greatest inhibition of the enzyme activity, was further separated by Sephadex LH-20 column chromatography. Fractions containing high condensed tannins reduced the growth of rice seedlings and suppressed the activity of β-cyanoalanine synthase. One of the purified biflavanols, which were isolated from peach roots as growth inhibitors, also inhibited the β-cyanoalanine synthase activity. We inferred that when the growth inhibitors suppress this activity, the normal cyanide metabolism is disturbed, resulting in the accumulation of hydrogen cyanide in the tissues. Thus from an allelopathic point of view, the growth inhibitors derived from the root residues of preplanted peach trees adversely affect the growth of replanted trees by causing cyanogenesis in their roots.
