Articles
EFFECT OF TEMPERATURE ON INITIATION AND DEVELOPMENT OF FREESIA FLOWERS
High temperatures delay the process of flower initiation.
The effect of radiation and daylength on flower development is variable and depends on temperature.
Modern culture techniques such as soil-cooling, and, probably in the near future, culture on rockwool, enable the grower to a better control of the environment.
This requires additional information on environmental factors involved in the processes of flower initiation and flower development.
This paper deals with the effects of temperature.
Three cultivars were planted each at different temperatures, ranging from 9 to 25°C. In all cultivars flower initiation started 5 weeks after planting in the temperature range of 9 to 15°C. Flower initiation was delayed by higher temperatures, and depended on the cultivar.
A delay was observed in ‘Blue Heaven’ when temperature was 16°C or higher, in ‘Ballerina’ 17°C or higher and in ‘Aurora’ 18°C or higher.
At temperatures which delay flower initiation the apex initiates more leaves.
At low temperatures 10–12 leaves and at high temperatures 15–20 leaves are initiated.
For optimal plant development, temperature is normally kept at a higher level for several weeks before it is decreased to the lower level, which is optimal for flower initiation.
A temperature of 20°C given for 3 weeks or more after planting before temperature is decreased to 14°C gives an increasing delay in flower initiation and reduced flower quality.
Experiments with ‘Blue Heaven’ at three soil temperatures (14, 17 and 20°C) and two air temperatures (approx. 16 and 19°C) show that the start of flower initiation mainly depends on soil temperature.