Basipetal Gradient of Axillary Bud Inhibition Along a Rose (Rosa hybridaL.) Stem: Growth Potential of Primary Buds and their Two Most Basal Secondary Buds as Affected by Position and Age

In Rosa hybrida L. cv. Ruidriko ‘Vivaldi’®, the effect of position on growth and development potentials of axillary buds was investigated by single internode cuttings excised along the floral stem and its bearing shoot. The experiments were carried out in both glasshouses and in a phytotron. The study firstly concerned the development of the primary shoot from the onset of bud growth until anthesis. The primary shoot was then bent horizontally to promote the growth of the two most proximal secondary buds, the collateral buds, already differentiated inside the primary bud. They gave rise to basal shoots. In the basipetal direction, the axillary buds along the floral stem exhibited both an increase in the lag time before bud growth and a decrease in bud growth percentage, demonstrating the existence of a physiological basipetal gradient of inhibition intrinsic to the buds or due to short range correlations. The same basipetal gradient of inhibition was observed along the floral stem and its bearing shoot, demonstrating that the age of the bud was not a major factor in determining the rate of bud growth. After bending the primary shoot, the percentage of collateral bud growth was also affected by the cutting position. The more proximal the cutting, the lower the sprouting ability of collateral buds. The growth potential of these buds appeared to be already determined inside the main bud before cutting excision.