Studies on the Soil Sickness Problem for Peach Trees

I. Cyanogenesis Involved in the Relationships between Root Sensitivity to Waterlogging and Soil Sickness

Abstract

Cyanogenesis involved in the relationships between root sensitivity to waterlogging and soil sickness in peach trees was investigated.
1. The cyanogenic glucoside in peach roots was predominantly prunasin and its level was highest in April and May, while lowest in August and September.
2. Waterlogging caused the rapid decrease in the level of prunasin and cytokinin activity in the roots and chlorophyll content in the leaves.
3. The anaerobic condition caused cyanogenesis in the roots, but the aerobic condition reversed it. The respiratory inhibitor, NaN₃ also caused cyanogenesis in the roots. There seemed to be some relationships between respiratory inhibition and cyanogenesis in peach roots.
4. More growth inhibiting substances were found to be excreted from the roots under the anaerobic condition than under the aerobic condition by the Avena coleoptile section elongation test. Benzoic acid and other UV absorbing substances were detected in the inhibiting fraction by TLC and GLC.
5. Benzoic acid also caused respiratory inhibition as well as cyanogenesis in peach roots. Therefore this suggests that for a poorly drained soil such respiratory inhibiting substances from the roots may be accumulated and become one of the causes of the peach replant problem.