JUGGLING EFFICIENCY. “Future shoot formation and light foraging indicate intelligent behavior. The morphology of many plants is constructed so as to minimize self shading. Leaves possess two light sensitive organs (the petiole and the pulvinus) that control the direction of the leaf lamina, ensuring it is intelligently placed at 90° to the prevailing polarity of incident sunlight thus capturing maximum energy.”
http://link.springer.com/article/10.1007/s00114-005-0014-9