Articles
A RE-APPRAISAL OF DIF EXTENSION GROWTH RESPONSES
Article number
435_4
Pages
57 – 64
Language
Abstract
Published data sets for petunia (Kaczperski et al., 1991), fuchsia (Erwin et al., 1991) and lily (Erwin et al., 1989) were re-appraised to determine if extension growth is determined by the difference (DIF) between day temperature (DT) and night temperature (NT) or by absolute DT and NT. It was found that, in all cases, quadratic models based on absolute DT and NT terms gave extremely good fits to the data.
Increasing DT gave increased internode extension in all three species, as found in tomato and chrysanthemum by Langton & Cockshull (1997), with indications of very high DT optima for extension growth.
The effects of NT were more varied.
In lily and fuchsia, increasing NT decreased internode length, the reverse of the situation in tomato, while in petunia, as in chrysanthemum, NT had little or no effect on internode length.
Models based on DIF ‘work’ only when DT and NT have opposite effects on extension growth as in lily and fuchsia.
Taking all five species together, it is concluded that while DIF is a concept that provides growers with a simple and effective way of appreciating growth responses to temperature it is, nevertheless, an artefact.
Extension growth responses are determined by absolute DT and NT.
Increasing DT gave increased internode extension in all three species, as found in tomato and chrysanthemum by Langton & Cockshull (1997), with indications of very high DT optima for extension growth.
The effects of NT were more varied.
In lily and fuchsia, increasing NT decreased internode length, the reverse of the situation in tomato, while in petunia, as in chrysanthemum, NT had little or no effect on internode length.
Models based on DIF ‘work’ only when DT and NT have opposite effects on extension growth as in lily and fuchsia.
Taking all five species together, it is concluded that while DIF is a concept that provides growers with a simple and effective way of appreciating growth responses to temperature it is, nevertheless, an artefact.
Extension growth responses are determined by absolute DT and NT.
Authors
F.A. Langton, K.E. Cockshull
Keywords
chrysanthemum, day and night temperatures, fuchsia, internode length, lily, petunia, tomato
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