TOPOPHYSIS AFFECTS THE POTENTIAL OF AXILLARY BUD GROWTH, FRESH BIOMASS ACCUMULATION AND SPECIFIC FRESH WEIGHT IN SINGLE-STEM ROSES (ROSA-HYBRIDA L)

Topophysis, the effect on growth and differentiation of position of ax illary buds along the shoot, was studied by propagating five-leaflet-l eaf single-node cuttings which were excised from seven stem positions and grown as single stemmed plants. In Rosa Rosa hybrida 'Korokis' Kis s(R), 'Tanettahn' Manhattan Blue(R), and 'Sweet Promise' Sonia(R) foll owing release of the buds from apical dominance by excision, morphogen etic development was studied until anthesis. The time from excision/pl anting until onset of bud growth, visible flower bud appearance, and a nthesis was generally shorter in plants originating from apical bud po sitions than From basipetal positions. Topophysis mainly affected the onset of axillary bud growth; the earliest growth and development was found in cuttings from the second uppermost node position. This node t ended to have the lowest plastochron value, which indicated the existe nce of a transition between sylleptic and proleptic buds. Stern length at visible flower bud and al anthesis generally increased as the cutt ing position changed basipetally until the second lowest position, and the number of five-leaflet-leaves at anthesis and the total number of nodes generally increased basipetally. For internode length, growth r ate, and fresh biomass efficiency the cuttings taken from the uppermos t and lowermost positions generally had significantly lower values tha n cuttings from all medial positions., At anthesis, plants originating from cuttings excised from lower medial positions generally had a hig her fresh weight, greater flower stem diameter, and a significantly hi gher specific fresh weight than those plants originating from apical o r basal positions. Among the cultivars, Sonia was the most efficient i n increasing fresh biomass and had the highest growth rate, whereas Ma nhattan Blue possessed the highest specific fresh weight, indicating a higher plant quality. It is suggested that topophysis in Rosa is an i ndependent phenomenon intrinsic to the axillary bud. (C) 1996 Annals o f Botany Company