How plants know when to flower

Scientists claim to have finally cracked a 80-year-old puzzle of how plants “know” when to flower — “it’s in their genes”.

A team at the University of Washington says that determining the proper time to flower, important if a plant is to reproduce successfully, involves a sequence of molecular events, a plant’s circadian clock and sunlight.

Understanding how flowering works in the simple plant used in this study — Arabidopsis — should lead to a better understanding of how the same genes work in more complex plants grown as crops such as rice, wheat and barley, Prof Takato Imaizumi, who led the team, said.

“If we can regulate the timing of flowering, we might be able to increase crop yield by accelerating or delaying this. Knowing the mechanism gives us the tools to manipulate this,” Imaizumi said.

At specific times of year, flowering plants produce a protein known as Flowering Locus T in their leaves that induces flowering. Once this protein is made, it travels from leaves to the shoot apex, a part of the plant where cells are undifferentiated, meaning they can become leaves or flowers.

At the shoot apex, this protein starts the molecular changes that send cells on the path to becoming flowers. Changes in day length tell many organisms that the seasons are changing.

The scientists investigated what’s called the FKF1 protein, which they suspected was a key player in the mechanism by which plants recognize seasonal change and know when to flower. FKF1 protein is a photoreceptor, meaning it is activated by sunlight.

“The FKF1 photoreceptor protein we’ve been working on is expressed in the late afternoon every day, and is very tightly regulated by the plant’s circadian clock. When this protein is expressed during days that are short, this protein cannot be activated, as there is no daylight in the late afternoon.

“When this protein is expressed during a longer day, this photoreceptor makes use of the light and activates the flowering mechanisms involving Flowering Locus T. The circadian clock regulates the timing of the specific phot­ore­ce­ptor for flowering. That is how plants sense differences in day length,” Imaizumi said in a release.