Variation in Translocation during the Photoperiod: Experiments Feeding 11CO2 to Sunflower

An array of 14 miniature Geiger counters arranged along petioleand stem has been used to follow the translocation kineticsfor ¹¹C assimilate in sunflower. Experiments over a 2 d periodindicate that (a) speed is insensitive to time of day and (b)the loading delay in the morning is comparable to that in thelate afternoon but smaller than that at mid-day. There is evidencefor substantial accumulation and retention of label along thepath on all occasions.