Abstract
To examine effects of root zone heating during the daytime on the flowering characteristics, growth and yield of strawberry plants (Fragaria × ananassa Duchesne ‘Akihime’) grown in substrate culture, Experiment 1 (September 26, 2005 to May 24, 2006) and Experiment 2 (September 26, 2006 to May 24, 2007) were conducted in a heated plastic house. Treatments in Experiment 1 consisted of 4 heating periods (0, 0.5, 2 and 6 h) starting from 05:00 for all treatment conditions. The mean root zone temperature during the daytime throughout the experiments was 16.2°C, 16.8°C, 18.6°C and 21.0°C, respectively. Treatments in Experiment 2 consisted of 3 heating periods (0, 2 and 10 h) starting from 6:00. The mean root zone temperature was 17.4°C, 19.3°C and 22.0, respectively. As a result, the flowering date of the 1st flower of each flower cluster was enhanced after the 2nd axillary flower cluster at the heating treatments in both experiments 1 and 2, because flowering duration between the clusters was reduced at the 2nd to 4th axillary flower cluster. With increases in the substrate temperature, the flowering duration was reduced and the flowering date was enhanced significantly. Finally enhancement of the flowering date at the root zone heating treatments increased one flower cluster, especially at 6 and 10 h heating treatments in Experiments 1 and 2. This increment resulted in the number of fruit harvested and marketable yield. Days to maturation and soluble solid contents of fruit were not affected by the heating treatment.
