A team of researchers has found that plants use phytochromes to sense nighttime temperatures. Phytochromes, which detect light during the day, act as thermometers when the environment is dark. This helps plants determine when to begin budding in spring. The details are in a paper that was just published in the journal Science.
Warm winters often mean early spring blooms for plants. Scientists have been unable to pinpoint the mechanisms behind this phenomenon, however. As climate change results in global temperature increases, understanding the factors that make crops bloom early becomes more important.
A large team of researchers led by scientists from the University of Cambridge studied a plant called thale cress (Arabidopsis thaliana) for twelve years. Arabidopsis is a common flowering plant and often considered a weed. The plant is hardy and easy to study, making it a popular model for plant biology research.
The team found that the plant’s phytochromes underwent molecular changes depending on light intensity. Phytochromes, pigments that help detect light, have long been known for their light-sensing roles in plants, fungi, and even bacteria. When activated by light, phytochromes bind to DNA and inhibit plant growth. Once it’s dark, phytochromes switch “off” and the plant is free to grow. This mechanism encourages plants to quickly grow and find light when, for example, they’re shaded by larger plants. At night, the phytochromes turn off as normal but the researchers noticed something interesting during the study. The rate at which the molecules deactivated was dependent on the environmental temperature. If it was a warm night they turned off quickly, encouraging plant growth. This explains why an unusually warm winter can encourage plants to bud and flower early.
The team’s findings finally provide a scientific answer for why warm nights lead to early budding. The authors believe that this knowledge could lead to the development of temperature-resistant crops that can better cope with climate change.
Jung et al. Phytochromes function as thermosensors in Arabidopsis. Science (2016).