May 7, 2013
Biological Science 2
Plymouth State University
Effects of Temperature on the Survival of Duckweed
Common duckweed is a plant found floating in compact colonies in ponds, marshes, lakes, and slow moving streams. Duckweed is a very tiny pale green, seed bearing plant (Wang and Messing 2012). Duckweed consists of 1 to 3 fronds, or an oval shaped leave–like structure (Wedge and Burris 1982). These fronds grow no bigger than 10 millimeters and usually serve to attach to other fronds, which create massive thick mats of duckweed (Wedge and Burris 1982). A small root-like structure, known as a rootlet, hangs below the fronds (Wedge and Burris 1982). Duckweed can spread very quickly and can cover the entire surface of a pond in a short amount of time. The growth of duckweed is common when the water contains high levels of nitrogen and phosphates (Wang and Messing 2012). Small amounts of duckweed will not harm a water source, but large amounts will stop the sunlight from entering the water. This can cause oxygen depletion, which can harm fish and submerged plants (Wang and Messing 2012).
Studies have found that duckweed is able to survive under several different temperatures. Duckweed is more cold tolerant than other aquatic vascular plants. There are conditions such as seasonal temperature change that can result in a morphological alteration to another form, called turions (Wang and Messing 2012). When the temperature lowers the energy stored in the duckweed during photosynthesis is transferred to starch biosynthesis, causing the starch to gather in turions (Wang and Messing 2012). Due to the amount of intercellular air space becoming less and starch increases the density of the tissue, the duckweed is able to sink to the base of the water where the organism is still able to live even if the surface of the water freezes (Wang and Messing 2012). When the warm conditions return the duckweed will...