Over the course of a few short weeks we have witnessed the transition of seasons. Colorful leaves are in full glory in the valleys yet at the higher reaches, winter is playing an icy hand.
Photo taken October 16, 2007
Photo taken October 9, 2007
Photo taken September 24, 2007
As mentioned in previous entries, there are remarkable changes occurring within the plants that we cannot even see. We take in the stunning results of the accumulation of sugars giving us the red colors and the unmasking of the cartenoids giving us the glowing oranges and yellows as the plant stops production of green chlorophyll. All of these visual changes are a result of shorter cooler nights and warm sunny days, yet deep within the plant tissues there are some other amazing shifts that are invisible to us.
One remarkable shift is the ability of plants to tolerate freezing. Dropping leaves is an important part of the process of preparing for colder temperatures and lack of available water, but plants actually adapt on a intercellular level to tolerate formation of ice. Now there is a problem of freezing inside cells (intracellular as opposed to intercellular) since the sharp crystals can rupture membranes, damage cells and kill the plant. The trick here is that plants confine ice formation to the areas between cells, thus avoiding damage to individual cells. The ability of plants to shift the ice formation from within the cells to the spaces around the cells has to do with metabolic shifts closely aligned with the changes in day length and cooling temperatures. A similar process takes place in several insect and frog species. Only they don’t advertise the changes with such a dramatic shift in color.