ISHS Acta Horticulturae 440: International Symposium on Plant Production in Closed Ecosystems
FORCING CULTURE OF FREESIA AND DUTCH IRIS USING SPOT COOLING SYSTEM |
| Authors: | H. Hirai, G. Mori |
| Keywords: | Dutch iris, flower abortion, forcing culture, freesia, spot air-conditioner, spot cooling, thumbing |
| Abstract:
Hot weather during summer season or early fall greatly affects plant growing in forcing culture of freesia and Dutch iris. At present, ventilation or shading of a greenhouse is carried out in order to keep the temperature inside the greenhouse low. However, thumbing of freesia (i.e., increase in distance between the first and second florets), and flower abortion of Dutch iris caused by high temperature cannot completely be avoided. To diminish these damages, spot cooling system was introduced by using a relatively economical spot air-conditioner in a greenhouse. The purpose of this study is, therefore, to investigate the effect of the spot cooling system on forcing culture of freesia and Dutch iris. In this experiment, two soil beds (1.0 m x 12.0 m each) were used in the greenhouse. One is a control bed which was naturally ventilated and the other is a spot-cooled bed. The spot-cooled bed was covered with tunnel-shaped film 30 cm in height to insulate the bed, and cool air was introduced into the tunnel from 20 September to 2 October in 1994. Freesia corms and Dutch iris bulbs were planted on each bed on 20 September. The mean air temperature on the spot-cooled bed was 5 °C lower and the mean soil temperature was 3 °C lower than those on the control bed. The distance between the first and second florets of freesia plants on the control bed was 6.1 cm and thumbing was observed and, also, the rate of flower abortion in Dutch iris was 12.5 %. Those on the spot-cooled bed were 3.7 cm and 0 % respectively. Thus, spot cooling using a spot air-conditioner was proved to be effective on forcing culture of freesia and Dutch iris. | |
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