City Creek Nature Notes – Salt Lake City

September 20, 2016

August 12th

Filed under: Insects, Plants, Red-Rumped Bumblee Bee, Sunflower — canopus56 @ 10:51 pm

Rotating Sunflowers

5 p.m. A recent article in Science magazine (Aug. 4) notes that young sunflowers track the Sun but that adults sunflowers face east. The authors speculate that juvenile sunflowers track the sun in order to maximize photosynthesis and their growth rate. They generate movement by deferentially adding new cells to one or the other side of the stem. In contrast, adult sunflowers face east and do not track the Sun in order to maximize shade for their pollinating insects. At mile 1.25 in the canyon, there is a row of roadside weed sunflowers. The afternoon Sun is in the southwest. I count the blossoms and all but one is pointing to the northwest or northeast. Only one bloom out of 20 points southwest towards the Sun. The blooms facing away from the Sun are covered with bumblebees. The same can be seen along 6th Avenue between F and H Streets where two homes have sunflowers in their front yards.


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