Last December was the warmest on record for Washington, according to the Washington State Climate Office. As the mild winter continues, many of the plants in our gardens are starting to show signs of small buds, even though it’s only February.
Takato Imaizumi, a University of Washington professor of biology, studies the genes that plants use to monitor seasonal changes. UW News asked Imaizumi to talk about how plants know when to bloom and whether this might change in warmer winters.
How do plants know when it’s time to bloom?
Takato Imaizumi: There are two major factors that plants use to sense the seasons: light — the presence or absence, the intensity, or the color at a specific time of day — and temperature. To control flowering time, plants sense light conditions in the leaves and temperature at shoot tips, which are buds that contain cells that allow the plant to grow and make a flower.
All plants use both factors, but some plants rely more on temperature than light. Some examples include tulips, crocus and cherry blossoms. Plants that rely more on light include mustard greens, cabbage, rapeseeds and chrysanthemum, though temperature is still important for these plants.
Other environmental factors that can affect bloom time include water and the availability of nutrients.
How do you think the warmer weather in December has affected the plants here in Washington?
TI: Temperatures will affect plant growth and development. I assume that warmer ambient temperatures will accelerate the flowering process of some plants that use temperature information to control flowering time.
But warmer temperatures could possibly lead to delays for others. While many plants are “dormant” and not growing during the colder winter months, some plants require exposure to prolonged cold periods before they can bloom — a process called vernalization. If the winter isn’t cold enough, these plants might not be able to initiate the flowering process.
Earlier flowering may be detrimental to plants if the weather gets cold again. That cold weather may kill them because they are no longer in their dormant phase. Also, plants that flower too early may misalign with their usual pollinators if the pollinators respond to different temperature cues.
How does studying the genes involved in the timing of plant flowering help with conservation biology?
TI: Proper timing of flowering is crucial for reproductive success and the health of a plant species. Understanding how the flowering genes are regulated will help us predict how future changes in climate may affect flowering times. That will give us a better sense of which plants may struggle.
This information could also help us design restoration strategies for plants that are struggling. For example, if we wanted to introduce a plant to a novel environment, we would have some ideas about what it would require to thrive. Plants are adapted to local environments. Even within the same species, a plant that lives farther north may require different light and temperature conditions to grow and flower compared to the same species growing farther south. When we think about transplanting plants for conservation, learning specific environmental requirements may increase the chance of transplant success.
For more information, contact Imaizumi at takato@uw.edu.