For this experiment Petri-dish A is fully exposed to the light source while Petri-dish B is partially exposed to the light. Independent Variable: We have chosen our independent variable to be the amount of light exposed to the cress seeds. Our first Petri-dish was allowed to be fully exposed to the light surrounding it, while the second was fully wrapped in black paper excluding a 0. CM slit directed towards the sun. Dependent Variable: Our dependent variable is the reaction/actions to the given conditions, for example he growth of the different cress seeds, the direction of growth or if it grows at all.
Controlled Variable: To keep the test fair we will control the variables by measuring each variable out. Our controlled variables are: Number of cress seeds in each Petri dish (1 5 each) Water absorbed by cotton wool (ml) The location of the Petri-dishes are at the same level and are both the same distance from the window. – this keeps the light source, the temperature and the supply of CA and 02 exposed to the plant the same. The room temperature fluctuates, but tot plants experience the same temperatures making the test fair.
The windows are kept closed because glass absorbs some of the UP light rays Size of cotton sheet used (1 Comic Com) Same water source used therefore no impurities Same type of cotton from same source Same type of plant (Cress seeds) Method: 1) Measure out the cotton and place inside both Petri-dishes 2) Pour ml of distilled water into each Petri-dish 3) Place seeds in at even distances from each other leaving enough space for them to grow 4) Take the second Petri-dish and cover it completely with black paper and cut a ingle 0. CM thick slit through the paper 5) Place the Petri-dish on a flat surface equidistant to the light source 6) Leave the project for a week and water crest seeds daily (1 Mol a day) 7) Write up observations of plant growth throughout the week and compare results Prediction: I predict that both plants will grow towards the light source. This is because the plant is adapted to find a light source so that it can photosynthesis, this means that the plant is positively photometric (can detect light).
This is done by Aquinas (plant ermines) elongating the darker side of plants so that the shoot will grow towards the sun. I also predict that the plants in Petri-dish B will grow at a slower rate, will have a higher degree of bend and will have a higher percentage of dead shoots. This is because without sufficient light the plant don’t have enough energy to grow as much. There is also a thin slit of sunlight for the plants in Petri-dish B therefore some plants may not be able to photosynthesis because there is not enough light for them to grow.