Temperature and the translocation of photosynthate through the leaf of Lolium temulentum.

Localized cooling of a 2 cm length of the leaf blade of the grass Lolium temulentum to 0° C, had only a small effect on the mass transfer of assimilates from the distal part of the leaf. There was no evidence of a reduction in the velocity of movement of (14)C-labelled assimilates through the low temperature zone, and the retention of assimilates along the pathway of movement was reduced by low temperature. In contrast to the longitudinal movement, lateral movement of (14)C, induced by steam killing sections of the leaf, was extremely sensitive to temperature and showed no sign of acclimatization, even after 3 days at low temperature. These results suggest that, although loading sugars into the transport system was sensitive to temperature, the movement of assimilates was not directly controlled by metabolic processes along the pathway.