Carbon loss from roots of wheat cultivars

The amounts of organic materials released into soil from roots during the first 4 weeks of growth were determined for 11 cultivars of wheat ( Triticum aestivum L.). Carbon loss from roots was measured by supplying 14 CO 2 continuously to the shoots and measuring the 14 C content of the roots, root-free soil, water-soluble material and CO 2 flushed from the root chamber. Six cultivars were compared in each of two experiments, with the cultivar Condor common to both experiments. There were no significant differences between cultivars, relative to Condor, for 14 C activity present in soil, roots, water-soluble material or rhizosphere CO 2 . There was a significant difference between cultivars in experiment 1, but not in experiment 2, for the variate log 10 ( 14 C lost from roots: 14 C translocated to roots). There was evidence that a reduction in growth temperature, within the range 10–15°C, increased carbon loss from wheat roots into the rhizosphere.