Comparing the Growth of Pea Plants Grown in the Light and in the Dark

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Comparing the Growth of Pea Plants Grown in the Light and in the Dark

Aim: To compare the vertical growth and weight gain of pea plants

grown in the light and in the dark.

Background Knowledge: Photosynthesis forms the basis for this

experiment. This is the process by which a plant makes food for itself

from the raw materials around it. The energy needed for photosynthesis

comes from sunlight, which is the variable for this experiment. The

substance that absorbs sunlight is chlorophyll, which is mainly

contained in chloroplasts. This energy is used to convert carbon

dioxide (CO2) and water into sugars. This conversion creates the waste

product oxygen, which is used by humans for breathing. Without being

able to photosynthesise plants will stop growing and die. In a plant

growing in the dark the chlorophyll will slowly be destroyed causing

them to use their food reserves. Once the reserves have been used the

plant will die. This is what happens in plants that are not grown in

sunlight. Etiolation is a phenomenon that occurs in plants not being

grown in sunlight, whereby the stem of the plant rapidly elongates to

increase the probability of the plant finding light. In order to carry

out this etiolation the plant must use its food reserves, so if the

plant does not find light having used these reserves, it will die.

Planning: I am planning to do an experiment over 3 weeks to find out

the effect light has on the growth of pea plants. It will take place

in an environment with controlled light, with equal amounts of plants

being grown in the light and in the dark. All elements of the

experiment other than light will be kept the same, such as amount of

seeds in each pot, amount of soil in each pot and amount of water

given to each plant each day. This will ensure a fair experiment.

Prediction: I predict that in general, the plants grown in the light

will grow better than those grown in the dark. To begin with the

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