The influence of root temperature on (14)C assimilate profiles in wheat roots.

The rate of translocation of (14)C assimilates from leaves to seminal roots in wheat seedlings was considerably reduced by lowering root temperature from 20° to 10° or 5° although the total translocation of (14)C to the roots after 24 h was little affected by temperature. The lowered root temperatures (particularly 5°) resulted in a more uniform distribution of assimilate along the roots than did a temperature of 20°, the ratios of radioactivity/cm in the apical cm, elongating zone, and basal parts of the root after 24 h being 14.0:9.6:1 in 20° roots by contrast with 2.8:1:1 in 5° roots. Temperature effects on assimilate distribution may help explain the observations that for roots grown below 15° ion uptake is sustained in older parts and that roots grown at a low temperature are thicker than roots grown at a higher one.