THE EFFECT OF DIFFERENCE IN TEMPERATURE REGIMES (DIF) ON POT CHRYSANTHEMUMS AND BEDDING PLANTS

The present heavy reliance on the use of plant growth regulators to control plant stature may be found unacceptable in the future and may be restricted by legislation as has already occurred in some European countries.
Application of growth regulators is expensive in material cost and labour use and ill-timed applications can seriously reduce the commercial value of crops.
Nevertheless, control of plant stature will remain a vital element in the growing of high value ornamental pot and bedding plants and to this end the DIF approach based on the manipulation of day and night temperatures may well have an important role to play.

Work carried out at HRI Efford during the winter of 1992/3 examining the use of DIF drop regimes at sunrise as a method of regulating growth of pot chrysanthemums and bedding plants are reviewed.
The treatments used were based on previous experiments at HRI Efford and growth cabinet work carried out at HRI Littlehampton.
An 8°C drop for 6 hours from sunrise was evaluated at different stages of production on 3 varieties of pot chrysanthemum and a 6°C drop for 2 hours was used on 8 bedding plant species.
The trials were conducted in a computer environmentally controlled glasshouse facility to enable accurate monitoring of temperatures and the crops grown under as near as achievable UK commercial conditions.
Various aspects of the use of DIF regimes will be presented and discussed.
Among these:

• growth control achieved using DIF drops at sunrise

• how achievable are DIF regimes by growers under UK conditions

• the potential cost of adopting such regimes as commercial practice

• an assessment of the effect of DIF drop regimes on the quality of pot chrysanthemums and bedding plants

Workshop on Environmental Regulation of Plant Morphogenesis

L. Sach

https://doi.org/10.17660/ActaHortic.1995.378.10