Saturday, December 31, 2011


A couple of weeks ago I asked my students to look at some "dead" twigs in lab. First I asked them to scratch the surface of the twig to note the green photosynthetic tissue beneath it. Having learned the basics of photosynthesis they understood that this tissue needed to have a source of carbon dioxide as well as a way to give off oxygen and water vapor. We then looked at lenticels under the microscope, the tiny structures that form on the epidermis of photosynthetic twigs, which allow gas exchange.

Lenticels and Gas Exchange

Examining these under the dissecting scope demonstrated that plants may look dead in winter but in fact are dormant. And even in a dormant state they are still metabolizing through photosynthesis and aerobic metabolism, no matter at a reduced pace.