Greenhouse growers and researchers have known for years that a key way to increase yield is through strict temperature regulation of the growing environment. For most species, the effects are clear and fast – control the day and night temperatures and you get less plant stretch, more branches, more flowers, and more fruit.
When daytime temperatures are much higher than nighttime temperatures, it sends a message to the plants to release gibberellin growth hormones which cause stem cells to elongate (aka, stretch). Conversely, if night temperatures are close to, equal, or even higher than daytime temperatures then the stretching slows and the plant can put more energy into creating new branch sites. The study of the effects on plant shape is called thermomorphogenesis and is a field of study stretching (o, pun!) back decades.
Calculating Your Temperature Differential (DIF)
Daytime temperature – nighttime temperature = DIF
Most of the time your DIF will be positive – it’s typically warmer during the day. It is possible, however, by elevating your night temperatures and/or air conditioning during the day to create a negative DIF. Some professional greenhouse growers will air condition for 2-3 hours during the morning to trick their plants into a strong negative DIF response.
Any time you are reducing the temperature of your plants there may be a small sacrifice in growth. The best application of this technique (depending on your plant species and desired outcome), maybe to elevate your nighttime temperatures, such as by using a heat producing CO2 generator, such as a propane or a natural gas CO2 generator.
Have experience using the DIF technique? If so, we’d love to hear about your experience!
Journal articles on this topic:
- Effect of diurnal temperature alternations on plant morphology in some greenhouse crops—a mini review
- Day and Night Temperature Differential (DIF) or the Absence of Far-red Light Alters Cell Elongation in `Celebrity White’ Petunia
- Thermomorphogenesis in Lilium longiflorum
- Effect of Day and Night Temperature on Internode and Stem Length in Chrysanthemum: Is Everything Explained by DIF?