Effects of harvest shoot stage on partitioning of photosynthates originating from bent shoots in the modified arching technique of cut rose production

By using a stable isotope method, partitioning of photosynthates was examined in a modified arching (MA) technique that achieved a high cut flower productivity to clarify how photosynthates produced by bent shoots are distributed within a plant at different developmental stages of harvest shoots. The translocation ratios from bent shoots at four days after harvest, eight days after harvest, for 10 cm-shoots, flower budding, and blooming were 44.0, 40.2, 51.0, 38.3, and 23.4%, respectively, and plants at the blooming stage had lower translocation ratios compared to those at the other developmental stages. The distribution of photosynthates produced by the bent shoot parts varied with the plant stage of the harvest shoots. The partitioning ratios of roots and crowns at four days, eight days, for 10 cm-shoots, flower budding, and blooming were 63.9, 53.5, 17.5, 26.6, and 81.0%, respectively. From these results, it was revealed that in the period from blooming to the next sprouting, roots and crowns were strong sinks. The partitioning ratios of mother stems were 36.2, 46.4, 7.2, 15.0, and 8.2%, respectively. We estimate that the mother stems are a strong sink right after harvest and absorb the photosynthates for the new sprouting. At the 10 cm-shoot and flower budding stages, photosynthates were partitioned to harvest shoots at 75.2% and 58.4%, respectively, indicating that they were distributed preferentially to vigorously growing harvest shoots. A total of 11.4% of the photosynthates were partitioned to harvest shoots at the blooming stage, suggesting that the photosynthates from the bent shoots were not involved directly in flower blooming. This study will contribute to improving the MA technique and cut rose production.