Students also investigate the properties and the importance of chlorophyll. Using paper chromatography, students find that the color in green plants consists of several chlorophyll pigments. Students explore the cellular structure of plant cells to observe chloroplasts in various parts of an Elodea plant. Students connect the role of chloroplasts to the process of photosynthesis. From these observations, students conclude that photosynthesis takes place in Elodea.
Through investigation, students observe that an Elodea plant in water and exposed to light performs photosynthesis. By using an oxygen meter, students can identify an increase in the amount of dissolved oxygen in the water containing the Elodea plant. This is a product of photosynthesis. Using the pH indicator phenol red, students will observe the change in pH of the water containing an Elodea plant. Students will correlate the observed change in pH to the use of carbon dioxide during photosynthesis.
in plants is dependent upon capturing light energy in the pigment , and in particular chlorophyll a. This chlorophyll resides mostly in the and gives leaves their green color. The range of light absorption in leaves is extended by some such as the , but does not cover the entire visible range - that would make the leaves black!
Some plants and plantlike organisms have developed other pigments to compensate for low light or poor use of light. Cyanobacteria and red algae have phycocyanin and allophycocyanin as accessory pigments to absorbe orange light. They also have a red pigment called phycoerythrin that absorbs green light and extends the range of photosynthesis. The red pigment is found in vegetables. Some red algae are in fact nearly black, so that increases their photosynthetic efficiency. Brown algae have the pigment fucoxanthin in addition to chlorophyll to widen their absorption range. These red and brown algae grow to depths around 270 meters where the light is less than 1% of surface light.
Chlorophylla-a is the primary for in plants. Its structure is shown at left. It has the composition C55H72O5N4Mg. It exhibits a grass-green visual color and absorption peaks at 430nm and 662nm. It occurs in all photosynthetic organisms except photosynthetic bacteria.
Immediatelyafter exposure to 14CO2, the plant's photosynthetic tissue iskilled by immersing it in boiling alcohol, and all of the biochemical reactions cease.
Mark the top of your bands and their origin
Chromatography is a good way to identify pigments and retention rates, but it may not be the best wayto measure photosynthesis.
Chromatography is a process where different compounds or pigments can be analyzed through separation.
Through experiments, students determine that carbon dioxide, light, and chlorophyll are three of the necessary components of photosynthesis. They also discover that during photosynthesis, plants produce oxygen and produce sugar, which is then quickly converted to starch.