Dry matter production and partitioning in rose (Rosa hybrida) flower shoots

Dry matter production and allocation to the different organs of rose (Rosa hybrida, cv. Dallas) flower shoots were investigated during three growth cycles (spring, summer and late autumn). The crop was grown under greenhouse conditions in a Mediterranean climate (Valencia, Spain). Fresh and dry matter, leaf area, and thermal time were determined at eight phenological stages of the flower shoot, from cutting to harvest. The increase in the shoot dry matter followed an expolinear function quite closely, suggesting that the shoot growth rate was near its maximum value at the time of harvest. The appearance of the flower bud drastically changed the dry matter distribution between the organs (stem, leaves and flower bud). Leaves were the first organs to be affected by the bud demand, showing a strong decrease in growth rate just after bud appearance. Stem growth rate was also affected, but later, and to a lesser extent. Flower bud growth was exponential until harvest. When expressed as a function of thermal time, dry matter partitioning was rather similar during the three growth cycles. Empirical functions are proposed that quantify dry matter partitioning in the organs of flower shoots as a function of thermal time. The overall results stressed the key role played by the flower bud in determining the dynamics of dry matter allocation in rose flower shoots.