Solar tracking by plants.
Leaves of many desert and agricultural species have the ability to move diurnally, orienting perpendicular or parallel to the sun's direct rays. This phenomenon is widespread in many plant families and occurs in both C(3) and C(4) photosynthetic pathway plants. In the annual flora of desert communities, solar tracking becomes more frequent as the length of the growing season decreases. Leaves that are perpendicular to the sun's direct rays for tracking appear to have high photosynthetic rates throughout the day, whereas leaves parallel to the sun's rays have reduced leaf temperatures and transpirational water losses.
Ehleringer
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Forseth
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