| Summary: | The roots of Pennisetum typhoides decomposing in normal field conditions, in sterilized soil inoculated with 15 rhizosphere fungi and in field soil maintained at various moisture levels produced vanillic acid. 3-4-dihydroxy benzoic acid and hydroxy cinnamic acid. These acids proved toxic to the rhizosphere fungi and seeds and seedlings of certain crop plants. Out of 15 rhizosphere fungal species inoculated to the soil only 6 could induce the release of toxins, moreover, the phytotoxic substances were detected from the washing of the roots collected only on the 30th day. The moisture range which showed liberation of toxins was 20-70 per cent. The time of liberation of acids in different set s varied. These were, however, frequently liberated from washings collected from roots decomposed for 15. 30 and 45 days.
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