1. Research question
Due to the fact that most plants have no appropriate apparatus to ingest and digest food, they have to obtain it by themselves using simple ingredients. That is why plants are called autotrophs or simply “self – feeders”.
The process of converting carbon dioxide taken from air and water from the soil into complex substances like glucose, is called photosynthesis and can be presented by the equation:
6CO2 + 12H2O ? C6H12O6 + 6O2 + 6 H2O
carbon dioxide + water ? glucose + oxygen + water
Oxygen, as a waste product, is released to the atmosphere.
Photosynthesis demands also a free energy taken from the sunlight that falls on the plant. After that, chlorophyll which is a green chemical substance contained in chloroplasts, in green parts of the plant, enables to trap it and use in the further process. Those organelles are filled with a matrix, called stroma and inside stroma there are membranes – thylakoids where photosynthetic pigments can be found. Thylakoids are grouped in grana.
Photosynthesis requires two steps:
a) the light-dependent stage in which the light energy is used to make high-energy molecules
b) and the light-independent stage in which a carbohydrate is produced.
My experiment will be geared for the first one because it involves the impact of the light.
Pphotosynthesis is affected by external factors such as the level of carbon dioxide, light intensity and the type of water.
Those are directly proportional to the rate of the process, however only until it reaches its limit just not to allow for the damage of a plant. Also the temperature should not be forgotten however this factor has not a significant influence on the whole process of photosynthesis (10-18 ï¿½C).
My target is to consider whether the concentration of carbon dioxide and the light intensity have an impact on the course of photosynthesis in an aquatic plant Elodea Canadensis. My researches will be done with use of the mineral, soda and tap water. Those three will be exposed to the sun light but to check the relationship fully, it is necessary to keep another sample separated – with a mineral water.
My predictions will be as follows:
First of all, the rate of photosynthesis will be the fastest in a tube with a soda water exposed to the sun light due to the fact that content of the carbon dioxide is higher than in the rest of samples. On the second place will be the rate in a tube with a mineral water exposed to the sun light because I presume that the abundance of macro elements such as potassium, calcium and magnesium which are
important nutrients for a plant, will allow for speeding up the process. However calcium and magnesium are also usually found in a tap water, after the process of the water treatment it may contain many other, not healthy substances, therefore the tube filled with this type of water will be on the third place. Finally, I am about an opinion that in a tube separated from the light the process of the photosynthesis will not occur.
In my experiment I have used variables:
a) dependent – the rate of photosynthesis (measured in seconds)
b) Independent – the light intensity (observed by naked eye), the concentration of carbon dioxide (measured in percentage), and the size of the plant (measured in centimetre).
I have used:
* 4 parts of the plant Elodea (of the same size – 5 cm length)
* 4 tubes (of the same size – 15 cm high, and a diameter 1,6 cm)
* 4 beakers (of the same size – 7 cm height, diameter 5cm)
* 140 ml of tap water
* 70 ml of mineral water
* 70 ml of soda water
* a ruler
* a digital stop-watch
5. Methods for the control of variables and collection sufficient relevant data
* To obtain results of the influence on the rate of photosynthesis I will observed by a naked eye produced bubbles
* The phenomena of producing bubbles will be checked two times after 10 and after 20 minutes of the experiment (those intervals will be controlled with use of a digital stop-watch with an error equals to 0,4 seconds)