Young sunflowers follow the sun and turn from east to west during the course of the day. During the night they reorient themselves to the east to begin the cycle once again. When sunflowers stop growing they permanently orient themselves to the east and wait for pollinators to visit. This phenomenon is called heliotropism and other plants display this type of “sun worshipping” behavior. The underlying mechanism behind sunflower heliotropism was unknown until researchers from the University of California (Davis) published their results on sunflower heliotropism in the journal Science. According to their findings, young sunflowers regulate growth of their stems based on an internal circadian rhythm through phased gene expression that increase cell growth in stems facing the west during the night. This allows them to bend east at sunrise. During the day, stem growth on the east side increases to allow the young plant to bend westward in the afternoon and sunset. Mature plants remain eastward oriented when growth slows to attract more pollinators. An eastward orientation increases the warmth of the plant which increases pollinator attraction.
About this Illustration: Watercolor and micron pen of a sun in motion over a field of sunflowers. You can now purchase merchandise with this illustration on it via RedBubble.