Abstract
The durations of the nuclear cycle and its phases were measured in the root tips of two cultivars of Triticum durum, Aziziah and Cappelli, by autoradiographic techniques. After labelling with 3H-thymidine the roots were allowed to grow in the absence of label for a period up to 26 hours. The average total duration of the mitotic cycle was found to be about 14h in Aziziah and 16h and 15′ in Cappelli. This time included in Aziziah a synthetic period of about 6h 30′, a post synthetic period(G1) of 4h 15′, a mitosis duration of lh and a pre-synthetic period (G1) of 2h 15′. In Cappelli the synthetic period was found to be about 9h 20′, G2 4h 45′, mitosis Oh 50′ and G1 lh 20′. The single phases duration was also considered as percentage of the total time.