A sunfleck is basically a bright spot or dapple of light. The term is frequently used in an ecological context to describe bright spots of light reaching the forest floor. They result from the random movement of tree leaves tossed about in a breeze on a sunny day. This has huge consequences for the plants living in the understory. Plants often acclimate to local light conditions by producing leaves adapted to full sun (curiously enough, called sun leaves) or to full shade (shade leaves). Imagine being a small plant growing quietly in the shadow of large trees. Suddenly a sunfleck arrives, bathing your shade leaves in brilliant light. What a jolt. Leaf temperature suddenly climbs, water rapidly evaporates from your leaf surfaces and photosynthesis rate goes way up. Then just as quickly, the light disappears. Back to normal, only to have the light return a few seconds later. No such thing as getting used to your environment, because it’s always changing. The transient changes in biochemistry produced by sunflecks are fascinating and are the subject of ongoing scientific study. For example click here or here.