Plants get the water they need for photosynthesis through their roots. The roots have a type of cell called a root hair cell - these project out from the root into the soil. Roots have a big surface area and thin walls, which allow water to pass through them easily.
Plants need water for other important things such as:
provide dissolved minerals that keep the plants healthy
provide a medium for transporting minerals
keep the plant firm and upright
keep the plant cool and hydrated
allow other chemical reactions to occur in plant cells
The purpose of adding sodium bicarbonate powder to the water increases the
amount of carbon dioxide in the water.
This investigation can be performed with water plants grown in many parts of
the world, except regions that have permanent ice.
are the tiny structures in plant cells where photosynthesis happens. Chloroplasts contain , a green pigment that absorbs light energy for photosynthesis. However, chloroplasts are not found in all plant cells. For example, they are not found in . These cells absorb the water needed by the plant for photosynthesis. However, since they are usually underground and in the dark, they are unable to photosynthesise anyway.
So the hypothesis that water is the nutrient used by plants was rejected.
Repeat John Woodward's experiment:
In August of 1771, , an English Chemist, put a sprig of mint into a transparent closed space with a candle that burned out the air (oxygen was not discovered yet) until it soon went out.
Repeat this Experiment:
In another experiment, Ingenhousz, placed a small green aquatic plant in a transparent container of water and exposed the container to bright sunlight.
In a series of experiments over as many as 77 days, Woodward measured the water consumed by plants.
For example, one plant showed a mass gain of about 1 gram, while Woodward had added a total of almost 76,000 grams of water during the 77 days of plant growth - this was a typical result.
Van Helmont believed that water was the source of the extra mass and the plant's source of life.
Repeat Helmont's experiment:
, a professor and physician at Cambridge University in the late 1600s, tried to design an experiment to test Van Helmont hypothesis that water was the source of the extra mass.
Animals that consume plants also make use of this energy, as do those that consume those that consume plants, and so on to the top of the food chain.
As important a job as making all of the world's food is, there's another vital function that photosynthesis performs: It generates the oxygen that oxygen-breathing animals need to survive.
In respiration energy is released fromsugars when electrons associated with hydrogen are transported to oxygen (theelectron acceptor), and water is formed as a byproduct. The mitochondriause the energy released in this oxidation in order to synthesize ATP. Inphotosynthesis, the electron flow is reversed, the water is split (not formed),and the electrons are transferred from the water to CO2 and in theprocess the energy is used to reduce the CO2 into sugar. Inrespiration the energy yield is 686 kcal per mole of glucose oxidized to CO2,while photosynthesis requires 686 kcal of energy to boost the electrons from thewater to their high-energy perches in the reduced sugar -- light provides thisenergy.
Prepare a graph of the collected data and analyze it.
(For each group of four students)
elodea (water plant) lamp (40 watt)
test tube razor blade (single-edge)
dechlorinated water (room temperature) tape
sodium bicarbonate powder (baking soda) clock or timer
metal stand with rod or test tube rack metric ruler
In the interest of genetic engineering and agricultural applications, the authors analyze the relative importance of genes that control both metabolic and light reactions as well as the structure, arrangement, and orientation of photosynthesis.