Effects of the High Day and Night Temperature Treatments on the Growth and Petal Coloration Rates in Eustoma grandiflorum Picotee Cultivar

Artificial climate experiments were conducted to investigate the main cause that the petals with low coloring ratio appeared in Eustoma grandiflorum picotee cultivar. The influence of high temperatures during the day and night on petal coloration rates was examined using six artificial climate chambers to replicate day and night temperatures of 25 and 15°C, 25 and 20°C, 30 and 15°C, 30 and 20°C, 30 and 25°C, and 35 and 20°C, from the vegetative stage to the harvest. Petals with a color ratio of >40% to the whole petal area appeared at day and night temperatures of 25°C and of 15°C or 20°C, respectively, which were also suitable for growth. The color ratio of the petals at a daytime temperature of 30°C fell when nighttime temperatures were above 20°C. The ratio of petals with <5% color relative to the whole petal area was 85% and no colored petals appeared slightly at daytime/nighttime temperatures of 30°C and 25°C, respectively. Moreover at daytime/nighttime temperatures of 35°C and 20°C, respectively, the ratio of colored petals to the total petal area was <30% and almost all of the colored petals had a color ratio of 5% to 20%. And other features of cut flowers such as cut flower length, stem length and number of flower buds were also fine.