Plants have an internal clock that measures the length of day and night, known as the circadian rhythm. This clock helps plants to synchronize their growth and development with the changing seasons. In a recent study, scientists have shown that plants also have a measure of the shortest day of the year, which they use to trigger the onset of flowering.

The study was conducted by researchers at the University of California, Davis. They grew Arabidopsis thaliana plants under different light conditions, and measured the expression of genes involved in flowering. They found that the expression of these genes was highest in plants that were grown under short-day conditions, and that the critical day length for flowering was the shortest day of the year.

This suggests that plants have an internal mechanism for measuring the shortest day of the year, and that this mechanism is used to trigger the onset of flowering. This is an important finding, as it provides new insights into the regulation of flowering in plants.

The researchers believe that this mechanism may involve the accumulation of a protein called CONSTANS (CO). CO is a key regulator of flowering in plants, and its expression is increased under short-day conditions. The researchers found that CO levels were highest in plants that were grown under short-day conditions, and that the critical day length for flowering was the day on which CO levels reached a threshold.

This suggests that CO may be the internal signal that triggers the onset of flowering in plants. Further research is needed to confirm this hypothesis, but the findings of this study provide new insights into the regulation of flowering in plants.

This discovery could have important implications for agriculture. By understanding how plants measure the shortest day of the year, scientists may be able to develop new ways to control flowering in crops. This could lead to increased crop yields and improved food security.