Relationship between the Accumulation of Putrescine and the Tolerance to Oxygen-Deficit Stress in Gramineae Seedlings

The accumulation of putrescine under anoxia was studied in seedlings of 6 Gramineae species showing tolerance to the stress in the following order: rice, barnyard grass>maize>rye, barley and wheat. The accumulation of putrescine in shoots and roots during 6 h of oxygen deprivation was different among the species and correlated with their tolerance to anaerobic conditions. In both tissues, rice and barnyard grass accumulated more than 0.6 μmol/g fresh weight. The lower increase in the putrescine titer was observed in wheat tissues with less than 0.1 μmol/g fresh weight. Feeding experiments with [l4C]arginine showed that rice tissues have a greater capacity than wheat tissues to synthesize putrescine under anoxia. The better tolerant species to anaerobic conditions showed high arginine decarboxylase activity in shoots and roots than the sensitive species. The presence of exogenous Put partially increased the survival of wheat roots after 7.5 h of oxygen-deficit stress. The role of putrescine in determining differences in the tolerance to anoxia in Gramineae seedlings is discussed.