6-Benzylaminopurine application enhances petal coloration of pink flowered chrysanthemums

During growing seasons with high-temperatures, anthocyanin accumulation in petals is low, resulting in poor coloration of the inflorescences in pink flowered chrysanthemums. To restore anthocyanin accumulation, 6-benzylaminopurine (BA) at 50 or 100 mg L^‑1 was applied to pink flowered 'Pelican' chrysanthemums at constant temperatures of 20, 25, and 30°C. BA-treated flowers displayed deeper pink petals at 25°C having intermediate L* and C* values compared with those at 20 and 25°C without BA. The amounts of two main anthocyanins, Cy 3-6”-MMG and Cy 3-3”, 6”-DMG, in the BA-treated flowers were higher than in the control flowers at 25°C. A higher concentration of BA (100 mg L^‑1) produced higher anthocyanin accumulation compared to that at 50 mg L^‑1 BA. The highest anthocyanin accumulation, which was significantly different from the control, occurred when BA was applied during the petal appearance to vertical stage (the petal elongated to the vertical position). However, accumulation was lower when BA was applied after petal expansion. This study demonstrates for the first time that applying BA is effective in enhancing coloration and pigmentation in chrysanthemum petals under elevated temperature conditions at 25°C.