Studies on the Fragmented Shoot Apex of Grapevine

Scanning electron microscopy (SEM) was used to provide direct evidence that shoots produced in vitro from fragmented shoot apices of grapevine were adventitious in origin. The effect of temperature on the formation of the adventitious buds was also examined using SEM. At 27°C, shoot buds were initiated by 31 d following fragmentation of the apex, while at 35°C shoot initiation and multiplication were already well-advanced at only 18 d after the start of culture. At 38°C, apical fragments quickly browned and died. After 25 d at 35°C, structures resembling inflorescence primordia were also visible. These did not occur in cultures at 27°C. The primordia later developed into multiple-branched tendrils, structures which appear to be intermediate between tendrils and inflorescences and have not been previously described.