白色バラ‘アバランチェ’の高温期の花色変化における発生条件の解明と対策

Abstract

Conditions under which the 'Avalanche' variety of white roses turns orange during high temperatures were investigated, to determine methods by which the color change can be prevented. The pigment responsible was identified as β-Carotene, it was measured in rose petals harvested under various conditions. Results indicated that the petals did not turn orange when cut flowers absorbed water at 25°C for 24 hours. However, the β-Carotene content increased afterwards when the flowers absorbed water at 3°C during the same time period. When cut flowers were pretreated at 20°C for at least 4 hours immediately after harvest and then refrigerated, the β-Carotene content decreased to 0.1 mg･100 gFW -1 , and at this level no discoloration could be visually detected. The β-Carotene content of the petals was highest when harvested 2 and 4 hours after sunrise. Furthermore, when the time of harvest and length of time cut flowers were kept in the refrigerator were varied, assuming harvesting and shipping, the β-Carotene content was lower when the flowers were harvested around 4:00 p.m., supporting the above results. β-Carotene was detected when the temperature exceeded 23°C during the growing period, and the higher the temperature, the higher the content. Results indicate that it is not practical to improve the growing environment, and that adjustment of harvest times, as well as pretreatment after harvest and before refrigeration, can help prevent color change in white roses.