VARIABILITY IN THE DISTRIBUTION OF PHOTOASSIMILATES ALONG LEAVES OF TEMPERATE GRAMINEAE

Gradients of photoassimilates were determined at various positions alo ng the length of mature leaves of wheat (Triticum aestivum L.) and Lol ium temulentum L. Attached leaves showed greater accumulation in the t ip region. This distribution was reversed in excised leaves illuminate d uniformly on the adaxial surface. Internal transport of assimilate w as detected both by sub-dividing excised leaves prior to illumination and by the administration of (CO2)-C-14 to the tips. The results are d iscussed in terms of the heterogeneity likely to occur in bulk extract s of leaf tissue and the ability of environmental perturbations to alt er the balance of assimilates within leaves as well as their overall c oncentrations.