Variation In Translocation During The Photoperiod - Experiments Feeding (Co2)-C-11 To Sunflower

An array of 14 miniature Geiger counters arranged along petiole and stem has been used to follow the translocation kinetics for nC assimilate in sunflower. Experiments over a 2 d period indicate that (a) speed is insensitive to time of day and (b) the loading delay in the morning is comparable to that in the late afternoon but smaller than that at mid-day. There is evidence for substantial accumulation and retention of label along the path on all occasions.