from “No Shrinking Violet”
by Cherie Winner
Washington State Magazine
Summer 2006

Plants don’t ‘eat,’ of course, but they do take in energy, in the form of light. They use that energy to convert CO2 and water into carbohydrates. Although plants can’t move to a sunnier or shadier spot like a sunbather going for optimal tan, plant physiologist David Kramer says some of them make smaller movements to control their exposure to light. They turn their leaves to intercept more or less light. They even rearrange their internal parts to enhance or diminish their energy intake....
Kramer says plants have another, even more subtle, way to control how much light energy they feed into the photosynthetic pathway. In weak light, they are incredibly efficient. Their light-gathering apparatus...send about 80 percent of the photons striking them into growth and maintenance activities.
In bright light, though, they pull the shades. Instead of funneling the light energy into the photosynthetic reactions, the antennae send up to 90 percent of it back out into the environment as heat...or risk being bleached and burned by the intense energy concentrated in their chloroplasts.
‘Basically, the plants are dealing with explosives,’ he says. ‘They need to drive all these reactions--but if they take in too much, they’re going to pay the consequences.’