* Solar refers to the sun itself or anything related to it. So, something "under the influence of the sun" could be described as solar-influenced.

* Heliotropic refers to the tendency of plants and other organisms to turn towards the sun.

* Phototropic refers to the growth of a plant or other organism in response to a light stimulus, usually from the sun.

* Insolation refers to the amount of solar radiation received by a surface.

The most appropriate term depends on the specific context of your question.