PLANT DIVINATION. “Future changes in resource availability are also predicted and acted upon. It has been known for some years that light reflected from green vegetation has an enhanced far red/red (FR/R) ratio and contains more blue light than normal sunshine. Many plants perceive these parts of the light spectrum and thus model the possibility of future, not current, shading from competitors and thus future reductions of available light energy.”
http://link.springer.com/article/10.1007/s00114-005-0014-9