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  • 1 Free University of Berlin Institute of Biology, Department of Biology, Chemistry and Pharmacy Berlin Germany 12165 Grunewaldstraße 34
  • | 2 BAM (Federeral Institute for Materials Research and Testing) Berlin Germany 12205 Unter den Eichen 87
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Thermal investigations using infrared (IR) thermometry and false colour thermography were carried out on flowering plants in the Botanical Garden of Berlin and in a private garden. Special interest went to phototropic plants that orient their blossoms towards a light source (mainly the sun) and within this group to solar trackers (heliotropism) that follow the path of the sun during the day. Best known among the latter is the sunflower. Bowl shaped flowers comparable to satellite disks focus the solar radiation effectively on their centre, resulting in a warming of the female organs at that point. Temperature differences above ambient can be as high as 10.7 K with a mean value of 6.0 K. Pollinating insects were often observed sun-basking in the bowls or on the flower disks attracted by energetic rewards in form of nectar and heat.

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