They use carbon dioxide from the air and water to make carbohydrates. This process requires an energy input – this energy comes from a light source. Plants need an adequate amount of light for the process of photosynthesis to occur correctly. When a plant photosynthesises it is providing itself with food to grow, without the component of light, a plant will not grow correctly because light is a limiting factor; I therefore predict that the cress seeds growing in complete darkness will become etiolated (they will be taller and thinner than the others; seeking any available light).
The seeds in full sunlight will grow to be shorter but stronger. Plan: 1. I will firstly collect my apparatus: 5 dishes with an equal diameter of 10cm (the dishes will be used as a base), 25 cotton wool pads (each dish will be layered with the cotton wool pads as a basis for the seeds to grow on), cress seeds, 5 equal sized shoe boxes (a dish will be placed into each box), 12 sheets of standard A4 paper (the paper will be used as light filters to decrease intensities), a syringe (to measure equal amounts of water for each plant), pins (to pin paper onto certain shoeboxes) and a ruler (to measure the height of the cress seeds after seven days.)
2. After collecting all the required apparatus I can now begin to set up my experiment. I will firstly cover the base of the dishes with one layer of cotton wool pads. I will then go on to place 70 seeds into each dish. I will then moisten the cotton wools pads with 15cm3 of water using a syringe. 3. I will then begin to set up my shoeboxes in preparation for the dishes to be placed in each. All the shoeboxes will be the same size, length: 28cm, Width: 20cm, Depth: 10cm.
Box 1 will have no lid, allowing full light to enter, Box 2 will have two sheets of standard A4 paper placed over the top, Box 3 will have four sheets of standard A4 paper placed over the top, Box 4 will have 6 sheets of standard A4 paper placed over the top and box 5 will have its original lid placed on it, blocking out all available light. (The paper placed over each shoe box will act as a filter decreasing intensities) I will now place one dish containing the cress seeds into each shoebox. The A4 sheets of paper will be held down by pins into each box, (one in each corner of each shoebox).
4. After the experiment has been set up I will now place all of my five shoeboxes outside on a balcony where they will all be facing the same direction, all dishes will be central in the box and the plants will receive equal amount of sunlight. 5. The experiment will be left to run for the next seven days, each day I will water each plant with 15cm3 of water. 6. After the seven days have passed I will begin to collect my results, I will measure the height of ten cress plants in each box, and I will measure them by using a ruler right from the base of the stem up to the top of the stem.
I will measure ten from each box to get a wider range of results which I can eventually take an average from. I will now record my results into a results table. 7. Now that I have carried out my experiment and have a set of results I will go on to draw my diagram, process my results onto a bar chart and finally write a detailed conclusion and evaluation. I also will state any modifications to my plan. Modifications to plan: As my experiment was in procedure I decided to make two modifications to my plan which were necessary but also beneficial to my overall results.