Heat stress to the developing floral buds decreases the synthesis of flowering pigments and scent compounds in the rose petals

We analyzed the floral pigments and scent compounds in rose flowers to investigate the effects of short-term heat stresses on the color and scent compounds of the developing flowers. Two cut rose cultivars, 'Penny Lane' (yellow) and 'Vital' (red), were used as the materials, which were treated with daytime heat stress of 37°C for three days when the flowering shoot reached the early floral bud stage (SI, 1 cm in floral bud diameter) or petal opened stage (SII), respectively. After heat stress at SI (HSI), 'Vital' produced smaller buds with fewer petals and bloomed earlier, compared to the control plants, but 'Penny Lane' did not really show such differences. However, the pigments and scent compounds were significantly influenced by HSI. In petal pigments, carotenoids in 'Penny Lane' increased by 43% but anthocyanin in 'Vital' reduced by 50%. The scent compounds fell 4-7% regardless of cultivar. The HSI affected the pigments more than the scent compounds. Heat stress at SII (HSII) influenced the flower mass or early flowering in both cultivars. Nevertheless, HSII typically reduced both pigments and scent compounds by 40-60% in 'Penny Lane', and also diminished anthocyanin by 20% in 'Vital', of which the main scent compound, 3,5-dimethoxytoluene, was never detected. Conclusively, the negative impact of short-term heat stress on the synthesis of pigments or scent compounds was revealed.