Photosynthesis, which occurs in plants, algae, and some bacteria, uses energy from sunlight to convert carbon dioxide into organic compounds. This is food, and plants need food to grow.
If you live in Massachusetts, you may have noticed that there has been what I would call NO SUNSHINE in all of June. Well, maybe there was one day, or two afternoons. Overall, though, there has been a noticeable lack of sun.
And, yet, my sunflower plants, along with the grass, hydrangea, hosta, ajuga, clematis, and all else that is green, have grown steadily. The tallest ones are up to my hip. In a rare and transient moment of June sun, Eli took their picture:
sunflower plants, 6.16.2009 at 6:25pm
Their continued growth is evidence that something continues to happen even though I might say that growing conditions are limited or unfavorable: wet, dark, cold.
What meager light we’ve had seems to have been enough.
Maybe it’s worth us remembering in our own lives that, even when conditions seem limited, subtle processes continue to unfold and yield good things: ones we don’t force, ones that surprise us.
leaf stitch word 
What great role models your sunflowers are.
As an aside to your story: during one of my recent walks through the Arnold Arboretum, I stopped to watch a woman hook up a machine to the leaves of a tree. I asked what she was doing, and she said, “Measuring Photosynthesis.”