Circadian Clock Controls Sunflower Blooms, Optimizing for Pollinators
Published:31 Jan.2023 Source:University of California – Davis
A sunflower head is made up of hundreds of tiny florets. Because of the way sunflowers grow, the youngest florets are in the center of the flower face and the most mature at the edges, forming a distinctive spiral pattern from the center to the edge. Somehow, florets coordinate so that they open in concentric rings starting from the edge and moving inwards on successive days, with a ring of female flowers always outside the earlier-stage, pollen-bearing male flowers.
An internal circadian clock controls the distinctive concentric rings of flowering in sunflowers, maximizing visits from pollinators, a new study from plant biologists at the University of California, Davis shows. The internal circadian clock of a plant or animal runs on a cycle of about 24 hours, allowing different genes to be activated at different times of day. Natural day/night cycles keep this internal clock synchronized to actual day time. Changing the length or day light, or darkness, can reset the clock. In sunflowers, continuous light disrupts the clock entirely.
Understanding how the circadian clock and the environment affect flowering will help breeders develop cultivars that flower at the optimal times of day to promote pollination, despite climate change and declining insect populations.