Behavior of phenolic substances in the decaying process of plants

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Abstract
The changes in amount of ether-extractable phenolic substances, individual phenolic adds, organic matter content, and pH value in the decaying process of rice straw were compared at 10, 30, and 50°C under moist and flooded conditions for 70 days. 1) The changes in pH value with time varied markedly according to temperature and water conditions. 2) Phenolic substances in the ether-extractable fraction obtained from the acidified solution of alkaline methanol extract contained undetected phenolic compounds in amounts larger than the phenolic adds detected by gas chromatography. pH value during incubation was hardly attributable to these phenolic substances because of their small quantity. 3) The changes in amount of the ether-extractable phenolic substances with time was mainly due to phenolic compounds other than phenolic acids, and influenced largely by the temperature and water conditions. Their formation and degradation took place rapidly at high temperatures under flooded conditions. 4) From the plots of individual phenolic acids vs. time, it was tentatively concluded that phenolic acids contalned in non-decayed straw were rapidly degraded in the earlier stage, and some of them were newly produced from ether-unextractable precursors in the later stage. These reactions occurred rapidly at high temperatures, especially under flooded conditions. 5) The content of p-hydroxybenzolc acid increased simultaneously with a rapid decrease in p-coumaric acid during the incubation ot straw. The relationship between vanillic acid and ferulic acid was the same.