Opis:
Organisms have many different strategies to survive winter. Some organisms burrow deep, others fly south, some loose leaves and become dormant, some hibernate, some have anti-freeze in their blood, and others over-winter as eggs. There are many different and fascinating strategies to survive long winters and freezing temperatures. Duckweed has a very unique strategy to avoid freezing at the surface of a pond. In late fall, as duckweed is reproducing by budding, it produces a special bud called a 'turion'. The turion continues photosynthesis but it takes the sugars it makes and combine them into starch molecules. The starch molecules are very dense and weight down the turion. The turion is more dense then the water around it so its sinks to the bottom. Ice is less dense than water so it floats to the surface. Ponds do not freeze to the bottom. Ice is always at the surface. Reduction of gases within the turion aids in increasing its density. In the spring when the ice at surface thaws, the turion breaks the starches back into sugars, increases the gas content and it floats back to surface.