Abstract
Investigations were carried out in order to clarify the effect of root temperature on the budbreak, shoot growth and development of flower clusters of‘Muscat of Alexandria’vines. Six-year-old vines were grown in the greenhouse under confined rhizosphere conditions. Forcing was started on December 18. The air temperature was kept above 18°C and 4 plots were used with root temperatures adjusted to 13, 20, 27 and 20-27°C. In the 20-27°C plot, the root temperature was kept at 20°C for 18 days until the start of forcing and thereafter at 27°C. In addition to these plots, two treatments were set to see their effect on budbreak promotion; 1) the air temperature near the branches was kept at 25°C and 2) garlic juice was painted on the cane sections.
1. Budbreak began earlier at 27°C than at 13°C, and elongation of shoots and development of flower clusters was more active in the former. Growth at 20 and 20-27°C was similar to growth at 13 and 27°C, respectively. Differences in the percentage of budbreak among the plots were slight. However, the number of sprouted buds per arm was greater at 27°C than at 13°C. Rooting occurred first at 20-27°C followed by 27°C and 20°C. Rooting in these plots occurred before sprouting, while in the plot at 13°C it occurred 2 weeks after sprouting.
2. High temperature treatment of the branches as well as painting of garlic juice promoted budbreak. Garlic juice in particular showed a significant effect on budbreak in all the plots. At 27°C, cluster development was so conspicuous that fully developed florets were observed even at the top of the cluster, while at 13°C development of the cluster was depressed. At 13°C garlic juice was less effective on cluster development and few florets per cluster were observed.
3. There were no significant differences in the percentage of berry set, total sugar content and titratable acidity of berries at harvest among the plots. Although the temperature control of the rhizosphere was terminated 3 weeks after full bloom, berries at harvest were larger at 27°C than at 13 and 20°C.
