Eterrie Rebeck, age 11, of Manitoba, B.C., Canada, for her question:

How many times a minute does a plant breathe?

A plant does not breathe in and out as you do. It has no lungs or nose to inhale and exhale Sts air. Instead, it has tiny pores called stomata all over its leaves and stems. The air seeps in and out through these miniature doorways. A few air molecules are going in while a few are coming out.

The air that gets inside the plant circulates among the living cells. They take the oxygen they need and return their waste carbon dioxide to the circulating gases. In dine, the carbon dioxide reaches the little air pores and seeps through to loin the air outdoors. Meantime, more fresh air bearing oxygen is entering the plant.